[HN Gopher] US companies are producing heat pumps that work belo... ___________________________________________________________________ US companies are producing heat pumps that work below -20F Author : jbrins1 Score : 212 points Date : 2022-12-28 13:19 UTC (9 hours ago) (HTM) web link (electrek.co) (TXT) w3m dump (electrek.co) | sneezesForAttn wrote: | We just installed a Solstice Inverter Extreme[0] before the the | storm hit. The low in our area was -24F. The heat pump is | advertised to work at -22F, but was still heating the house at | the low. Efficiency and capacity are reduced with as the | temperature drops. We have backup resistive heat in the buffer | tank of our hydronic setup. It is early but we are happy with the | performance during this first cold snap. | | [0] https://www.spacepak.com/solstice-inverter-extreme | maxerickson wrote: | What's the rough cost? | | (obviously there will be lots of variation based on the | complexity of the install, but the ballpark is still | interesting) | sneezesForAttn wrote: | About $10k for the heat pump. NPV is positive for 10 years | compared to a propane boiler. This doesn't include | installation, but it is doable for the advanced DIY | homeowner. | | The entire system cost $25k + installation. Not cheap, but in | our climate we heat 7+ months and it is worth it. The | extended federal tax credits help, but our state does not do | anything in terms of rebates. | DIVx0 wrote: | I recently bought some land in Minnesota on a lake. I really want | to do a 'no compromise' off-grid setup. Water and septic wont be | a problem but I am worried about the heat. | | I plan to install a huge solar array with a battery house. I'd | like to run everything off electric, including the heat. | | I am in early days of thinking about this and I have time to | plan. Anyone have insights on electric heat in ultra cold | environments? I assume I can simply scale up a solar array and | battery capacity to meet needs (dead of winter, with spans of | cloudy days). The only fossil fuels I want on property are for | equipment and if I must have it, a backup NG generator. | | I don't know anyone who runs heat pumps in MN, I'm sure there are | some but most folks are burning NG or wood pellets. Electric heat | seems relegated to secondary needs, like base boards or heated | floors. | | *edit cloudy | jupp0r wrote: | If you do some back-of-the-envelope math on this, you'll notice | that this will be cost prohibitive to implement using | batteries. | mrinterweb wrote: | I have a Mitsubishi Hyper Heat, and it operates to -13f, which | would be unheard of in Western Oregon (where I live). So long | as your house is well insulated, you'd likely be fine with a | heat pump. Pay attention to R-Value for insulation, but if you | choose the right materials, that goes a long way for heat | storage. | | I know there exceptions in Minnesota where it can get | considerably colder than -13f, but I don't know how long those | super low temps are sustained. You would definitely need some | sort of emergency heating system. An outdoor propane tank (the | larger variety) and a propane heater would likely do the trick | as an emergency backup. Not great for air quality in your | house, but plenty of people use that as their normal heating. | inthepipe wrote: | [dead] | zamalek wrote: | Look up ground-sourced heat pumps. You store your heat in soil | during the summer, and draw it out in the winter. | vitaflo wrote: | I want this someday too (also live in MN). Wood pellets or just | a wood burner are your best bets for secondary heat. I grew up | in WI and we only had electric base boards and a wood burner | (then pellet stove). Get the house up to 85 before bed and by | morning it's in the high 50's and start the fire again. You | need to be ok with fluctuating temps to really make it work. | | You mention cloudy days but the one positive about our brutally | cold winters is that when it's below zero it tends to be sunny | out. If you set up your solar to extract as much sun as | possible during these times, as well as build your house with | large south facing windows with stone or concrete flooring you | will not need to heat the house much during even the coldest | days (solar radiation will heat the house and the concrete | flooring will release what heat it gained in the evening). | Qwertious wrote: | Keep in mind that you don't need a traditional electrical | battery for heat - storing heat directly is _extremely_ cheap, | you just need insulation and thermal mass (i.e. sand /rocks, | any old crap will do). There are a fair few systems that use | easy summer-solar to generate heat, store it for months at a | time and then release the heat in winter. | | It scales up really well thanks to the cube-square law, which | is a euphemistic way of saying it's hard to make a viable | system that's really small. But if you're off-grid because | you're in the middle of nowhere, then you can spare a few | square meters anyway. | [deleted] | nashashmi wrote: | Can they work in pair with co2 capture? Assuming neg 20 deg is | co2 liquid point ? | londons_explore wrote: | The needs of the homeowner and the needs of the grid are at odds | with one another here. | | The electricity grid wants the highest possible efficiency on the | coldest days, so that they can serve as many users as possible | without building more infrastructure. | | The homeowner wants the _average_ efficiency to be as high as | possible over the whole season, to reduce heating /cooling costs. | They don't care if one or two really cold days have bad | efficiency, as long as the system has sufficient output to keep | the house comfortable. | | Someone needs to use laws or incentives to align those two - | because if every home owner used one of todays heat pump systems, | then the electricity grid would fail on the coldest days of the | year. | itake wrote: | If my power goes out (due to ice storms or hurricanes) and I | need to rely on a local power supply (battery, solar panels, | gas generator), I would like my AC to be as efficient as | possible. | londons_explore wrote: | I didn't explain clearly... AC systems don't have a single | efficiency number - they have different efficiencies | depending on the indoor temperature, the outdoor temperature, | and the number of kilowatts you want delivered. | | You can generally design any AC system to work efficiently at | any specific combination of those variables - but if any | variable deviates far from the optimum design point, | efficiency will drop. | | So the real question is, not "I want an efficient system", | but "I want an efficient system when it is 20F outdoors, | because that's the temperature most of the year". | jnsaff2 wrote: | Are there even heat pumps where efficiency goes down when the | delta-T decreases? | londons_explore wrote: | Yes. If the cold side gets too hot, the pressure on the | compressor input gets too high, which means the compressor is | doing far more work with every stroke - and input electrical | power goes up massively. The motor overheats and the thermal | cutout stops it. When the motor is cutting in and out | efficiency goes way down. | | This is an issue with fridges. When you buy a new fridge and | first turn it on, it's called a 'pulldown'. The compressor | gets far hotter than it ever normally gets in normal | operation. Most fridges are only rated for 3 pulldowns in | their lifespan - and if you do more than that and the fridge | fails, they'll claim it isn't in warranty anymore. And in | modern fridges, the software keeps track of how often so they | can deny the warranty claim too... | the-alchemist wrote: | If you want an (entertaining) deep dive into heat pumps, I can | recommend Technology Connection's | https://www.youtube.com/watch?v=43XKfuptnik and its followup, | https://www.youtube.com/watch?v=MFEHFsO-XSI | moffkalast wrote: | Do we really need heat pumps that work that far into the | negative? You can always turn on an internal resistive heater to | compensate after all. | | Not quite something you can do on the other end though, when | trying to cool with exceptionally high ambient temperature. It's | such bullshit that the physics of this universe does not allow | for resistive cooling. | eppp wrote: | Resistance heat is extremely expensive to operate. Burning | something is cheaper. | zdragnar wrote: | The problem is that if everyone comes off of fossil fuel heat | and switches to heat pumps, you need a grid that is capable of | delivering enough eletricity to power simultaneous resistive | heating to every house... because every house is going to need | resistive heating at the most dangerous time to not have any | heat at all. | | These cold snaps tend to also coincide with extreme winds and | other weather events that can take out power lines, so a | stressed grid just compounds the issue. | jupp0r wrote: | On top of that, it's also the time when you need the most | energy for heating because it's the coldest. | EVa5I7bHFq9mnYK wrote: | My AC runs just fine at -15C (+5F), the problem is when | temperature swings between zero and sub-zero, it causes formation | of the ice in the outer unit which can break the fan. | kwhitefoot wrote: | Some heat pumps designed for low temperatures have heaters to | avoid the freezing of condensation. | lizknope wrote: | I'd like to see an efficiency curve of this heat pump at -20F, | 0F, +20F, +40F | | I have a heat pump that can be used for both cooling an heat | along with a natural gas burner. The installer has set the system | to use the heat pump at 40F and above and switch to natural gas | at below 40F below based on the efficiency of the heat pump | dropping at low temperature. | | My heat pump is a SEER 18 unit primarily for cooling in the US | south so I'm sure a heat pump designed specifically for northern | cold climates will be more efficient than mine at low temps but | I'd like to see how much. | newZWhoDis wrote: | Well that installer cutoff was likely waaaaay too high. Your | heat pump should be fine to 30F, maybe even 25F before needing | gas. | | Modern systems are 24 SEER and good to -5, and these research | units take that to the next level. | bowow wrote: | Unfortunately only the very top-of-the-line (very expensive) | variable speed compressor units are rated for anything close | to 24 SEER / -5F (unless that's what you meant by modern | systems). | rudedogg wrote: | > Well that installer cutoff was likely waaaaay too high. | Your heat pump should be fine to 30F, maybe even 25F before | needing gas. | | The parent post was saying it's cheaper to use natural gas at | those temps, so that's why the installer did the cutoff | there. | | You can look at COP numbers for heat pumps here: | https://ashp.neep.org/#!/product_list/ | Majromax wrote: | > Well that installer cutoff was likely waaaaay too high. | Your heat pump should be fine to 30F, maybe even 25F before | needing gas | | One possibility might be that the unit lacks de-icing | circuitry. If that were cut for cost optimization, the unit | would still work fine for cooling and for moderate- | temperature heating, but anywhere near 30F it would ice up | and stop working. | sokoloff wrote: | > "additional efforts are needed to address common technical and | market barriers to wider adoption by consumers - which include | performance at temperatures of 5F and below, installation | challenges, and electricity grid impacts during peak demand | periods." | | There are definite market barriers at play. In my house in New | England, I tried to replace my aged boiler with an air-to-water | heat pump (after carefully verifying, via experiments during a | cold week in February, that my heat distribution would indeed | work fine at a supply of 130degF). Only one company was even | willing to come out and provide a quote and their quote was | around 2.5x the costs of "put another boiler in", such that the | payback period would be "literally never". | | If, after doing the research to find out about them and | specifically seeking one out, I couldn't manage to make an air- | to-water heat pump make sense, I doubt that very many of them are | being sold. I suspect it's one of those items that, if more were | sold, more firms would sell/install them, bringing the costs into | the realm of economically reasonable (and lowering the risk of | having a difficult-to-support heating plant in the decades to | come). | lizknope wrote: | I watch the PBS show This Old House which takes place in the | Boston area. The plumber / HVAC guy Richard Trethewey is a fan | both ground ("geothermal") and air source heat pumps including | the air source heat pumps that work at 0F and heat water for | radiant floor heating. I'm surprised that more companies aren't | doing it there. | maxerickson wrote: | The majority of their projects are pretty high end (and they | tend to want to demonstrate new technology, because it's more | interesting). | throw0101c wrote: | For the 'project homes', perhaps, but if you're going to go | through the effort of building new or re-doing an entire | structure, you might as well use the latest and greatest | stuff/practices/code. | | They also have many segments of smaller DIY jobs for | simpler fixes/maintenance, e.g.: | | * https://www.thisoldhouse.com/plumbing | panzagl wrote: | The 'cast' of 'This Old House' is mostly MIT MechE grads who | figured out they could make more money doing renovations for | Route 128 techies than burning themselves out working at | their companies. | [deleted] | throw0101c wrote: | Oh yeah, Richard Trethewey and Tom Silva are definitely MIT | guys: | | * https://www.thisoldhouse.com/21071273/richard-trethewey | | * https://www.thisoldhouse.com/21071309/tom-silva | | * https://www.thisoldhouse.com/cast | panzagl wrote: | Well, they've done episodes like this: | https://www.thisoldhouse.com/season-20-ask- | toh/23197052/s20-... | throw0101c wrote: | Advanced technology being developed at advanced research | labs: who would have thought? | | But that doesn't change the fact that hosts are mostly | 'regular folks' in the trades that hook up a bunch of | wiring and pipes (or glue/nail/screw together a bunch of | wood). | panzagl wrote: | I had 'cast' in quotes for a reason- I was half thinking | of Norm (though I don't think he went to MIT) and more of | the various sub contractors that filter through the show | (some of which seemed to be thinly disguised product | reps). Still, you can't deny they were higher quality | outfits than anything most of us are likely to run into. | caycep wrote: | I haven't watched since a kid w/ the Bob Villa days.... | ngetchell wrote: | No they are mostly second and third generation trades | people. | laidoffamazon wrote: | I mean that did describe Car Talk | ableal wrote: | > their quote was around 2.5x the costs of "put another boiler | in", such that the payback period would be "literally never". | | Doesn't that depend on the costs of both energy sources? | | Last year I made a similar choice, albeit at smaller scale, | just for one water heater. Picked an electric heater with heat | pump, also cost 2.5x more than plain electric, but 1/3 the | energy cost. It will take a few years to pay back ... | sokoloff wrote: | > Doesn't that depend on the costs of both energy sources? | | Yes, it depends on the costs and efficiencies of the | competing energy sources, the difference in capex, the annual | building heat load, the projected lifespan of each source, | annual maintenance costs, and the interest rate. | linuxftw wrote: | I recently spoke to a well driller that also does geothermal | well drilling. He was telling me that the systems are more or | less obsolete at this point, as the air-to-air units have such | a high SEER rating that the ground loops really will never pay | off. | benmanns wrote: | Is geothermal any quieter? I was assuming the ground loop | pump would be quieter than the air-to-air fan. | sokoloff wrote: | There's no outside noise in a ground-source system (for all | practical values of noise: it's just flow in insulated | pipes). The pumps are nearly inaudible inside the | mechanical room as well. | | Inverter-based air-source outdoor units are nearly | inaudible during any time when your neighbors are likely to | have their windows open. When the weather is uncomfortable | enough to have the units need to run at high-speeds, they | are no longer inaudible, but the neighbors are likely to | have their windows closed. | zacharycohn wrote: | I'm looking at a system now that is 45 decibels - 10db | quieter than my robovacuum which is one of the quietest in | the market. | implements wrote: | What attracted me to geothermal was the year round | availability of 50F water - easier to extract winter heat at | that temperature, and you could create a simple fan / | radiator ducted air cooling system for the summer. The latter | would actually store summer heat in the ground, and could be | powered purely by solar. | Bedon292 wrote: | I have been doing a bunch of research into geothermal | recently and this doesn't seem to match with what I have | seen. But it probably also varies a lot by location and such. | | They appear to still be about twice as efficient as an air to | air one, and have less parts and maintenance (no outside unit | to deal with). Yes the initial install is a lot higher | because of the drilling but that should last for decades. In | the US there is also 30% rebate at tax time which helps cut | the costs down a bunch too. | linuxftw wrote: | You're looking to spend at least $30k if you need a | vertical system, probably a lot more. And from what I | understand, they ground loops inevitably don't reach their | expected lifespan, so you'll be drilling new holes sooner | than later. | | If you live in a very cold climate, I suppose with tax | credits it could make some sense. For most people, AC + | Natural gas is the cheapest way to go. | dashundchen wrote: | Was it a company that also did gas boilers? | | If it's not a company that solely does heat pumps, I have heard | a lot of contractors will give outrageous estimates because gas | is simpler for them and they don't want to do it without the | huge markup. | | I had ground source heat pump installed with vertical wells in | a city by a dedicated geo installer. The cost with tax credits | came out not much more than a high end gas furnace and water | heater. Going airsource would have been even more cost | competitive, especially with the federal tax credits in place | starting in 2023. | sokoloff wrote: | They did. To (only partially) guard against that, I made it | clear that I wouldn't be hiring them to hang a gas boiler. | (That still allows them to prefer someone else's gas boiler | job over my air-source job, but at least prevents me bidding | against myself.) | | And there definitely would be more labor, more piping, and | more electrical work to switch to an ASHP; that's part of the | market forces problem that is hard to overcome with anything | other than large price increases for gas or larger direct | subsidies for switching. | CoastalCoder wrote: | My house uses a heat pump + oil-burning furnace. It gives a | pretty good combination of efficiency, and ability to handle | really cold weather. | toomuchtodo wrote: | I think this is most of the way to what the future looks | like: a high efficiency heat pump with cogeneration, so you | can still burn propane or natural gas for heat and limited | power to drive the heating system in an emergency (and if you | don't have gas service to the premises, you have either a | propane tank [1] or an exterior outlet to hook up outside). | You must have a solution for when utility power is down for | substantial periods of time. | | During the winter storm that just passed, a friend in the | Midwest called that their house had no power and was rapidly | cooling. The utility could provide no ETA to resolution. I | walked them through (over the phone) safely enough | backfeeding enough power from a gasoline generator (outside, | with the extension cord run through a basement escape window) | into their furnace circuit to bootstrap the furnace (and run | the blower fan) to keep the house warm so that the pipes | didn't freeze and burst. If the HVAC system had had a small | battery and some way to generate power from the heat it was | burning, the gasoline generator would've been unnecessary. | Perhaps an integrated thermoelectric generator [2]? A standby | generator isn't financially practical for most folks ($6k + | install). | | (EDIT: to the safety folks out there possibly concerned, the | furnace breaker and main breaker were tripped, and the meter | was pulled to prevent any chance of harm to electrical | linemen from inadvertently energizing the utility line; take | no chances with safety, do not attempt this at home) | | [1] https://www.amerigas.com/about-propane/propane-tank-sizes | | [2] https://patents.google.com/patent/US5427086A/en | throw0101c wrote: | > _A standby generator isn 't financially practical for | most folks ($6k + install)._ | | An Honda EU2200i generator costs US$ 1400 (and less | expensive generators can probably be found): | | * | https://powerequipment.honda.com/generators/models/eu2200i | | You also need an external plug, a cable going from that | plug to a sub-panel, and a line going from the sub-panel to | the main panel with an interlock device for safety, if you | wish to avoid running extension cords. | | There are dual-fuel generators that can also use either | gas/petrol or propane, and some tri-fuel generators that | could also be connect to a natgas pipes (and conversion | kits that can be added to propane-capable generators). | phil21 wrote: | The Honda EU2200i can be aftermarket modded to run tri- | fuel. I did it to mine just in case, and currently have | it set to run propane. A simple swap of a small part will | let it burn natural gas instead. | | I also like that I don't have gasoline to deal with - I | can stock up a 20lb propane tanks and generally forget | about it. Rotating gas is a giant pain if you keep enough | on-hand for an outage of any appreciable amount of time. | toomuchtodo wrote: | Would you mind sharing a link to the part you mentioned? | sokoloff wrote: | https://www.amazon.com/Grenergy-Gasoline-Conversion- | Generato... | phil21 wrote: | https://www.hutchmountain.com/products/honda- | eu2200i-propane... | | If you are at all handy this is probably a 30 minute job, | it involves cutting a single hole for the propane tank | connection and otherwise can be done with a screwdriver. | | It's been reliable for me going on 4 years now - although | I only really have run the generator for maybe 100 total | hours since then. | | I haven't looked for some time, but there are also other | kits on the market. I those these guys due to reputation | on forums, and how clean it is to install. | mindslight wrote: | The problem is that while all that electrical work is a | weekend project for a DIYer, it's quite expensive to have | a professional do it. So then you start bundling things | (since I'm already paying thousands, maybe I'll just | splurge for that Generac with the auto tranfer switch...) | | (FWIW, I believe there is an aftermarket propane | conversion kit for the EU2200i. Converting a gasoline | engine to run on propane is straightforward) | sokoloff wrote: | For others interested in preparing for a situation like | this, here's a video laying out in reasonable detail what | to do.* | | https://www.youtube.com/watch?v=1JNuovFpCpQ | | * I don't like that they skipped putting a bushing or an NM | clamp on the back of the box into the furnace, but | otherwise the video looked sound when I watched it a couple | weeks ago. | jchw wrote: | I've been waiting to do this in the event of a power | outage; that said, I'm really curious what the current | draw of my furnace blower will wind up being. There is a | label that suggests it has a peak draw of 8.5A, but that | seems like a lot. Still, it seems like a nice backup plan | in the event of an outage, even if I only have a couple | kWh worth of battery storage. | a9h74j wrote: | Many furnaces use third-party controller boards with | well-known suppliers. You might find in the furnace | manual that there are different wire-to-board | permutations to allow different fan (interior | recirculating blower) speeds. From home testing a few | years ago, I recall RMS currents 50%-80% of peak rated | draw, but could be mistaken. | mikeyouse wrote: | What's the model number of your furnace / blower? I've | been doing a ton of research in this area as I'm | remodeling my place and have several furnaces and duct | loops to deal with. | | From what I've seen so far, unless your unit is super | old, the 8.5A is almost certainly just a 'peak' startup | current that's overstated as well. Your blower should say | something like "1/3 HP" and from there it's | straightforward conversion of 1HP = ~750W so a 1/3HP | would be 250W. On a 120v service, that's 2 Amp. With | maybe 15% efficiency loss, at peak speed, the blower | motor wouldn't be drawing more than 2.5A. It could/will | draw more than that to start, but literally just for a | second or two. | jchw wrote: | Thanks, that's useful! That was my thought w.r.t. startup | current, since I assume it is an inductive load. The | model is a Carrier 58STA090-14 and it is indeed 1/3 HP. | Seems likely I could run that load off my car in a pinch, | which is definitely a good option to have available. | mikeyouse wrote: | So per the spec sheet -- the "Full Load Amps" for that | model could actually be up to 5.2A per the bottom portion | of the 90-14 column second from the right on page 5: | | https://d1049ui2fjityy.cloudfront.net/userfiles/inriver/d | ocu... | | That motor has a switch so it could be in 3 different | settings -- As shipped, the blower motor speed is set to | be faster for AC (more draw in the summer) to prevent the | coils from icing over, and then it's shipped to be the | slowest fan speed while in heating mode, but it is | possible that your installer changed that. If indeed it | is in the "slow" speed for heat, then 2.5A would be about | right. | mynameishere wrote: | I don't know what's up with that, but the standard fix is | to let the faucets trickle. | toomuchtodo wrote: | Challenging when you're on a well and your well pump | requires power. Will your generator support 220V and the | surge start a well pump requires? That surge is going to | occur every X minutes to replenish the pressure tank as | it depletes due to trickling. In this scenario, driving | the 15A furnace circuit was a more simple fix. | | Something else to consider: electric pipe heat cable to | keep pipes from freezing draws ~7 watts per foot, is | quick to install, and easy to power if you've planned | ahead. | mynameishere wrote: | I guess I must plead ignorance once again. Maybe flushing | the pipes would be possible? I just know I would | electrocute myself screwing with anything more powerful | than a laptop battery. | sbierwagen wrote: | Houses designed to be vacant in freezing temperatures | will have a drain port at the main shutoff valve so the | pipes can be fully emptied. | | Unfortunately, this is not a universal feature in | residential construction. | sokoloff wrote: | I happen to have valves that would allow me to drain | almost all of my house to prevent freezing, but that's | not universally the case (and even in my case, I couldn't | drain the hot water tank fully without power without | letting it just flood the basement). | | Freezing pipes is one concern, though having heat for the | humans is another pretty desirable thing, so if I could | spend effort on something that would result in drained | pipes and no heat or on something that would result in | enough heat in the house to make that unnecessary, I'm | going for option #2 every time. | [deleted] | lizknope wrote: | I was also without power last week for 6 hours. | | I have a SEER 18 heat pump for cooling which can reverse | for heating in the winter but it also has a natural gas | burner. Based on the installer's advice we set the system | to use the heat pump if the outside air is 40F or above and | switch to natural gas below 40F. | | The problem was that when the power was out the electronics | in the system could not communicate with the thermostat in | the house. My Nest thermostat literally said there was no | system connected. I wish there was some kind of UPS to | power those electronics and the blower fan. | jacquesm wrote: | Can't you just hook up a sizeable computer UPS for that | purpose? That should run it for long enough to get you | through most outages. | sokoloff wrote: | The heat pump will be a 240VAC load. Consumer-level | computer UPSes in the US are 120VAC. | | The 24VAC transformer for the control circuitry will be | on one of the 120VAC legs, but it's likely the installer | didn't specifically wire it to allow partial powering of | just the transformer and electronics board. | jacquesm wrote: | Hm... you might be able to get away with ordering a EU | UPS then, those are 240V, you'll have to add a center tap | transformer and maybe mess around a bit with it to get it | to output 60 Hz (that will only improve efficiency). | alpos wrote: | There is, an inverter sized for the load with an auto | transfer switch attached to a set of 100ah batteries will | do what you're looking for. And that is what a UPS is on | the inside. They just tend to use terribly small | batteries. | | Such setups are easy to build if you want it and running | a 100-200w blower doesn't require too many batteries | either. However, if you need to run a compressor, the | number of batteries required to power that for 6hours | would start to get cost prohibitive. | | https://www.amazon.com/s?k=2000w+pure+sine+wave+inverter+ | aut... | | https://www.amazon.com/s?k=220v+automatic+transfer+switch | +50... | | https://www.amazon.com/s?k=100ah+lifepo4+battery | | This guy has accumulated essentially everything you could | want to know about such setups, at any voltage, any | reasonable power range, in various applications: backup | systems, full off-grid, mobile power. | | https://www.youtube.com/@WillProwse | | https://www.mobile-solarpower.com/ | | For a 240v load, there are inverters that output 220v or | you can use one inverter to power each hot line, just buy | the batteries at the same time from the same manufacturer | and ensure they will stay balanced. In your case you | could also use a cheaper manual transfer switch if you | don't mind going into the closet to flip it when the | power goes out. | illegalsmile wrote: | What model do you have? I currently have a boiler for | hydronic baseboards and would like to move to a more all | in-one-solution for heating/cooling that is predominantly | electric. My goal is to move all my gas appliances to | electric with solar but it would be great to have gas | backup and gas for those cooler days. | jabart wrote: | New homes should be built to better insulation standards. | You have to solve so much and use so much energy to solve | for a drafty house or lack of insulation on the outside | walls. Newer homes are factoring in the R-value of 2x6s and | finding ways to insulate those now. | | In this scenario, high efficiency heat pump with a backup | gas fireplace. Those typically don't require any | electricity to run as they can ignite off AA battery or a | push button. My PC battery backups barely last 30 minutes | on a wifi router because of conversion loss. Furnace fans | also account for up to 1/3 of energy usage of a unit. | Cogneration would add $5-10k to a home build versus a 50 | gallon propane tank with a single emergency gas fireplace | unit. | toomuchtodo wrote: | Most of the heat from a fireplace goes up the flue | unfortunately. It's one of the least efficient heating | sources per the dept of energy (~15% efficient). A low | tech solution is more thermal mass perhaps in high | performance dwellings. | | Wood burning furnaces are a challenge because homeowners | insurance providers don't want to insure dwellings that | use them (but will if certain conditions are met, such as | it not being the primary hearing source, professionally | installed, etc). | jaggederest wrote: | Wood stoves are really efficient these days, hitting 70% | plus, and it's Carbon Neutralish(tm) as a fuel source | (obviously uses fossil fuels for harvest and transport | and such, but that's only some percentage of the total) | | I'm always amazed at the ability of our questionable | 1990s wood stove to happily heat the entire house. It's a | great backup heat source on days when it gets proper cold | out, which is thankfully rare here. | throw0101c wrote: | > _Most of the heat from a fireplace goes up the flue | unfortunately._ | | Depends on the fireplace. Direct-vent gas fireplaces take | outside air for combustion and then exhaust it, with no | inside air being used in the process. There are also | direct-vent wood _stoves_ that can do the same. | | Wood stoves can get about 85% combustion efficiency, but | that's not heat-delivered efficiency (often 10-20% | lower): | | * https://www.epa.gov/burnwise/energy-efficiency-and- | your-wood... | masklinn wrote: | If you've got wood available, you could also have a wood | furnace as backup, and / or an actual fireplace (an | efficient one ideally, possibly a masonry heater if you | have the space and foundations to handle that load). | patentatt wrote: | This is a great solution too. I have a wood 'heatilator' | (or fireplace insert) and during the recent cold snap in | the Midwest I went through about 1/4 face cord of kiln- | dried oak over 3 or 4 days (that's a lot by my | standards). It kept the gas furnace mostly idling and the | home warm (in the 80's by the fireplace actually, lol). | Probably not exactly cost efficient with the cost of wood | these days but I like being able to take some of the load | off the gas furnace. | Scoundreller wrote: | Problem is high efficiency furnaces/boilers require a | powered vent, so they need quite a bit of power to operate. | And then you'd need to circulate "cold" air/water against | the heat exchangers. | | This usually adds up to several hundred watts. | alpos wrote: | Up in the northeast power goes out every winter. It also | gets restored a lot faster than the midwest, personal | experience, but the reliability of it going out at some | point during the winter means that everyone has a wood | stove and a backup generator. Portable ones are practical | enough and wiring a couple of circuits and a plug for the | generator is not cost prohibitive for most. | | What I've found in traveling the whole country for a few | years is that local power generation or storage always | forces you to consider just how little power you actually | need. You can pretty much never just power the whole house, | or even a whole RV. Even 50amps is ALOT of power and trying | to provide that from solar/generator/batteries is | incredibly expensive. | | So your real question is pretty much never going to be, | "how do I power my whole house in an outage?" but rather, | "What is absolutely essential to spend up to 3000w on?" and | even then knowing that a generator putting out 3000w burns | 20lbs of propane in about 4hrs and 3000w for 4hr on | batteries would require 10 to 12 100ah lithium batteries at | $350+ each. | | I still agree with you that super efficient heat pumps are | the future without fossil fuels but that probably also has | to come with greatly improved insulation values in almost | all homes regardless of region. Think double the current | DOE recommendations. If you're running on electricity, you | will feel the cost of every bit of heat you lose through | the walls, roof, and windows. More insulation is a one time | cost versus monthly, it always makes sense in the long run. | | However, we'll need regulation to force home builders to | invest in that instead of just adding unnecessary sqft that | people never use but have to heat and cool anyway. For some | reason people don't want to pay extra for a house that is | well built and well insulated, they'd rather go with bigger | is better even when it's already absurd, and builders have | noticed this. | jcadam wrote: | My house uses a NatGas boiler and in-floor radiant heat. It | also has wood stoves for those -20F (or worse) nights when I | need a little supplemental heat (or the power is out and the | main heating system is offline). | | A heat pump would be a waste up here in Alaska esp given I | don't need A/C. Just opening the windows and running some | fans in the summer tends to do the trick for cooling. | throw0101c wrote: | > _Just opening the windows and running some fans in the | summer tends to do the trick for cooling._ | | The problem with 'natural' ventilation is you also get | things humidity, pollen, dust, _etc_ coming in as well. | | One of the major advantages of mechanical ventilation (like | HRV/ERVs, which cycle the air) is that things are tempered | and filtered beforehand. Sometimes you also want to deal | with individual variables: the temperature is fine, but the | humidity is off. | a9h74j wrote: | Is filtering incoming air (for a mix) necessarily the | norm, though? Even in the rare high-performance homes | built on spec[ulation], my sense is that filtering | incoming air might be omitted, in favor of a single | filter acting on recirculation. | sbierwagen wrote: | It wasn't the norm, but now that more people have pollen | allergies and widespread summer fires are common again, | it's become more important. | jcadam wrote: | And forced air can be quite dirty (dust/pollen/etc.) if | you don't clean your ducts regularly. | jcadam wrote: | There's the expense of maintaining a central A/C, | ductwork, etc., that I'd rather not deal with (not to | mention electricity is expensive here). Yes, if the air | outside is dirty (forest fires, volcanic eruption, etc.) | you've got a point. HEPA filters can help some with this, | I suppose. | | Humidity isn't usually a big issue here most days. If | anything, it can be a bit dry (but not as dry as running | an A/C would make it). Though, I do have a portable | dehumidifier I use when I need to :) | wmeredith wrote: | Mine is the same with a gas furnace/heat pump combo. It's | great. | euroderf wrote: | My use case is similar. The oil furnace feeds hot water into | a network of radiators. My design goal is to maximize the | electricity outage that we can make it thru without frozen | pipes, and it has to be on a budget (so no generator or giant | UPS). | | The house is mostly unoccupied (a second home). Operation in | an outage has to be fully automatic - it needs an automatic | transfer switch I guess. The typical indoor temperature is | just 5.5C (42F) - this does not leave much margin for the | house to cool down during an outage when outside is like -5C | (or -10 or -20). | | But it turn out that an oil pump and a water circulation pump | do not draw THAT much power, so if I can run them off backup | power (say, a new car battery plus an inverter), it should | last for some time before ice has any chance to form. | ethagknight wrote: | Anyone know how these pumps manage to squeeze enough heat out of | ambient air to make it worth the while? -20 is down there! I | understand how heat pumps work, but what's the differentiator? | contravariant wrote: | It helps if you look at it as temperatures in Kelvin, to bring | something from 250K to 300K requires a 20% increase, which can | be done by an ideal engine at an efficiency of 300/(300-250) = | 6. Sure you can't ever reach that ideal but the upper limit is | high enough to make it worthwhile. | | I'm not fully sure at what point it stops being worth it, but | anything above 150K can get an efficiency of more than 200%, in | theory at least, and 150K is way above any reasonable ambient | temperature. As far as I know the ideal is not even that hard | to approach it's just how to do it in small scale and quickly | that is the problem. | fallingknife wrote: | What does an efficiency above 100% mean? | Qwertious wrote: | It's a multiplier for the electrical input - if your heat | pump is 400% efficient, then it means the electricity is | being 100% turned into heat, plus 3x as much heat is being | sucked in from outside. | supertrope wrote: | Instead of burning fuel to generate e.g. 1500W of heat, a | heat pump uses 500W of electricity to transfer heat inside | generating the same 1500W heating effect. | contravariant wrote: | It means you transfer more heat than work put into the | system. | yosito wrote: | > -20 is down there! | | That's 244 Kelvin. It may not seem like a lot of heat to the | human body, or judging by the state of everyday elements like | water. But in terms of energy, there's actually still quite a | bit there. | ape4 wrote: | -29C for non-Americans. Its a prototype. | Ottolay wrote: | The issue with heat pumps is that most of the ones currently | being installed in South East of the US don't work well below | +20F let alone 0F or -20F. Most of them are being installed with | an electrical resistive backup heat, which is incredibly | inefficient. | | The problem is when a cold spell like Christmas 2022, with | temperatures down towards 0F. All the heat pump users switch to | resistive backup heat and it overloads the electric grid and we | get rolling blackouts. | | In my opinion, heat pumps are amazingly efficient at moderate | cold temps, but they really need propane or wood heat backup for | the really cold temperatures instead of resistive heaters. | newZWhoDis wrote: | We've had heat pumps that work down to -5F for years. If you're | installing one that can only go to 20F in 2022(3?) something is | very wrong. | | Backup heat methods increase the complexity and cost. | Ottolay wrote: | I am just saying what the typical install is in the South | East US. The heat pumps installed may produce some heat at 5F | but they can't keep the temperature to the set value, so | there are resistive elements (Aux heat) to make up the | shortfall. | | It's pretty common for people with heat pumps to have Aux | Heat kick in during cold spells, which cause power grid | overload issues. | | I realize you can insulate a house well enough and have a | good enough heat pump to avoid backup heat, but 5F or 0F days | are rare enough that the codes do not enforce this. | bowow wrote: | When I researched this year on replacing my A/C / Propane | Furnace system with a heat pump, I found that companies | didn't seem to want to advertise what temperatures their heat | pumps can operate effectively at. If I look at some marketing | materials from Google it seems companies like Carrier and | Trane are only willing to talk about their heat pumps working | in low temperatures if it's regarding their top-of-the-line | (very expensive) variable speed compressor units. No one | talks about what temps the mid range units can handle, and | I'm guessing it's because they don't work well below 20F. | mrinterweb wrote: | My heat pump is advertised to operate as low as -13F. One | thing to note is the efficiency of heat pumps is not optimal | when they are operating close to their extremes. | haberman wrote: | What is inefficient about resistive heat? Isn't | electricity->heat basically 100% efficient? | | Maybe you are saying that heat->electricity->heat is | inefficient, since most electricity is produced from heat | inefficiently. | | I always get tripped up by this, since I live in an area where | almost all electricity is hydro. In that case resistive heating | seems fine. | zdragnar wrote: | Electricity offers resistive heating, and heat pumps. Heat | pumps are much more efficient than resistive heating. | | Otherwise, you have chemical fuel which burns, and a bit of | electricity to pump it around (either by forced air or water | pumps). | | In terms of electrical input, resistive heating is the worst | of the lot, even if it can be sourced in a carbon neutral way | (unlike nat gas or fuel oil). | 1123581321 wrote: | In the US, anyway, when people say electric resistance heat | is inefficient they are comparing it to natural gas heat. | It's the same story in water heaters; if you install a HPWH | you are betting on not needing to resort to resistance heat | because if you do that too much, you probably should've | installed a cheaper gas unit instead. (I'm a happy HPWH owner | weighing the timing of adding a heat pump for central heat.) | thatcherc wrote: | That 100% efficient figure is correct - you get one Watt of | heat for one Watt of electricity. It's just that heat pumps | can deliver 3 or 4 Watts of heat for each Watt of electricity | (usually quoted at around 300% or 400% efficiency!). Compared | to that, resistance heaters aren't as efficient. | | The explanation that made the most intuitive sense to me is | that it takes less energy to move heat from one place to | another (air at 273 Kelvin to air at 300 Kelvin, like a heat | pump does) than it does to create heat from nothing (like a | resistor does). That's why the heat pumps can get deliver | more heat to you from the same amount of electricity. | haberman wrote: | That makes sense, but GP was calling resistive heating | inefficient compared with propane or wood heat, which | doesn't make sense to me. | bluGill wrote: | The best natural gas power plants are 64% efficient. A | modern furnace is around 95%. Sure electric restive heat | is 100% efficient in your house, but the whole system us | much worse. | | Of course electric can come from many sources, if your is | renewable at the time resistive is good. However you | might also be using some old 1920s coal generator that is | 10% efficient (these still exist, but are only used in | the worst emergencies) | anikom15 wrote: | Natural gas (not sure about wood; in most areas it's | abundant) is about 1/3 of the cost of electricity in | America, so it's economically less efficient. | ARandumGuy wrote: | Resistive heat is 100% efficient, but heat pumps can operate | at greater then 100% efficiency. That's because a heat pump | doesn't actually generate heat, but just moves it around. | Even when it's cold outside, there's still a lot of heat | energy in the air, which can be moved inside to warm your | home. | | Due to the increased efficiency, heat pumps are better then | electric resistive heat (when temperatures outside are within | the heat pump's operating range, that is). This is regardless | of the method of power generation. | gibspaulding wrote: | Since heat pumps are moving heat around rather than actually | producing it, they can be effectively better than 100% | efficient so it's not so much that resistive heat is | inefficient, but that it's less efficient than a heat pump. | brilee wrote: | I wrote up a brief discussion here on the boiling points of | refrigerants https://www.moderndescartes.com/essays/refrigerants/ | | The long and short of it is that if the heat pump works below | -20F, then the boiling point of the refrigerant must be below | -20F. This, in turn, implies a higher pressurization (as per the | Clausius-Clapeyron eq) required in order to achieve a T_hot of | 80F (or whatever output temperature you want. The higher | pressurizations require more expensive components and | compressors. | Scoundreller wrote: | Maybe I'm dumb, but aren't compressors pressure-agnostic? They | just add pressure, right? | | Other than needing to be a bit stronger to keep from bursting | against the higher delta with the ambient atmospheric pressure | like the rest of the components. | zip1234 wrote: | Even if you do need to make thicker pipes, strength in a | metal generally increases with the square of the thickness, | so it doesn't cost twice as much in materials to double the | strength. | londons_explore wrote: | This isn't true. For pipes, double the pressure requires | double the wall thickness, which requires double the | material. | | However, I don't think raw material cost is a big part of | the cost of refrigeration systems anyway. | dragonwriter wrote: | > For pipes, double the pressure requires double the wall | thickness, which requires double the material. | | Double the wall thickness requires more than double the | material. | samtho wrote: | The "soft" copper tubing they use in refrigerant lines is | not only very cheap (it's not 100% copper) but is very | much over built for pressure it is likely going to be | subject to. It's way cheaper, in this instance, to simply | sell a line set that works with 99% of systems instead of | having dedicated factory lines and consumer confusion | from having different grades of registrant tubing. | SnowHill9902 wrote: | Power for compressible fluids is approximately proportional | to the relation of pressures not difference. | Cerium wrote: | In this case there is a higher delta between the system and | the atmosphere as well as a higher delta between the hot and | the cold side, which is what requires a stronger compressor. | Gibbon1 wrote: | I had a HVAC guy mention that seals are problematic always | with non hermetic compressors. Everything larger than a | fractional HP system has a shaft seal between the | compressor and the motor. Small systems being a pain | because there is less refrigerant and no way to monitor the | amount. | warmwaffles wrote: | There is a way to monitor it, but you'd need to put in | T-Junctions and add a pressure sensor on the high and low | pressure sides. You'd then need to rig up some system to | read those pressures. But _you_ would be unfortunately | the one that has to do it because I don't think there are | any off the shelf solutions. | mindslight wrote: | The ideal model of everything is everything-agnostic. | | Refrigeration stuff is generally soft copper, and modern | refrigerants are already working up in the hundreds of PSI. | So I can see that getting expensive or requiring a sea change | in materials. | eloff wrote: | If they're using copper, changing materials would probably | save money. Copper is comparatively expensive. I suspect | your premise that they are using mostly copper is | incorrect, but then I write software for a living, what do | I know. | loeg wrote: | Copper is (very) effective for conducting heat. Aluminum | is also pretty effective but obviously has different | material properties than copper. It might be a good fit | here; I don't work in the space. | bluGill wrote: | Aluminum generally has fatigue limits that mean it will | fail eventually, releasing refrigerant (which is normally | an environmental disaster) | dylan604 wrote: | what qualifies as a disaster? the amount of refrigerant | in a consumer unit just doesn't seem like a lot even if | 100% of it was released. if it was a continuous supply, | then maybe it could get disaster level, but these are | closed systems with a finite amount. at these levels, it | seems to me that just driving one's car would qualify as | an environmental disaster. | adonovan wrote: | If a typical large split system has about 10Kg of R410A | (GWP = 2000x CO2) that's about 20 metric tonnes of CO2. | Compare to 5 tonnes for an average passenger car per | year. So a leak is like four years of driving a car. | | Is it a disaster when an invisible odorless gas escapes | and no-one notices? Or when a tree falls in forest? Not | on its own, but our entire crisis is a pile of sand | grains each too small to count. | dylan604 wrote: | My real point was accident vs disaster. Whether anyone | knows about it or not (someone will know when the AC | doesn't work and the repair tech sees it being empty). If | one house looses coolant, then I'd call it an accident. | If a vendor has a major problem during manufacturing so | that the majority of units fail, then maybe we can use | bigger words. | Retric wrote: | The issue isn't just the 1st one that breaks the issue is | the other 100,000+ that do. | dashundchen wrote: | The newer refrigeratants that require higher pressures | are much better for ozone and have a lower global warming | potential. | | Pentane and isopentane, R601 being one of them (of course | flammability is a problem) and R744 which is just CO2. | kazen44 wrote: | aluminium also has the problem that it is a dissimaler | enough metal from most other plumbing hardware (being | either made of brass, copper or steel) that it will | result in the buildup of a lot of gunk because the | aluminium disolves. | eloff wrote: | That's galvanic corrosion, but it's usually an issue in | water. I don't know that it would be a problem with | refrigerants, likely not. | pjc50 wrote: | Copper has long been the choice for piping because it's | soft enough to bend without cracking. The obvious #2 | choice, stainless steel, is often even more expensive. | | (I don't like the standard HN analysis technique of | assuming that another field has made a really basic error | that can be spotted by an autodidact from outside) | etrautmann wrote: | While I generally agree with your response to the | perceived arrogance - shouldn't we all ask if we can do | better than assuming someone else is an expert and has | fully optimized a solution? As long as we approach new | domains with a sense of humility and respect I think it's | desirable to always be looking for better solutions. | mindslight wrote: | > _assuming someone else is an expert and has fully | optimized a solution?_ | | I wasn't offering my own singular expert [0] opinion, but | rather pointing out what I've observed the entire | industry has seemingly converged on. Despite being | subject to the hyper-cost-optimization of the consumer | market, every refrigeration appliance I've seen still | uses copper heat exchanger tubes and copper piping. | | I would welcome someone chiming in saying something like | "actually I work in HVAC and things are moving towards | aluminum heat exchanger tubes and stainless piping" or | "that's already the case for most new building-scale | systems", because I'd learn something new. But "just | asking questions" based on one single material property | isn't particularly helpful. | | And yeah, copper has gotten expensive. That has helped | some new technologies displace it (eg PEX), but copper is | also still used where it's needed (eg PEX and PEX | fittings over 1" nominal (which is equivalent to 3/4 | copper) are prohibitively expensive for some reason). | | [0] In fact, I'm not a refrigeration professional, and | have yet to pretend to be one. I just tend to look at how | things are built. | eloff wrote: | First off, I was upfront about my ignorance. Secondly, | copper is way more expensive than stainless steel, unless | I'm missing something. More than 8x according to random | websites on Google. | | I'm sure there is a reason copper is used, but if the | industry has to find an alternative, it would likely be | cheaper. | mindslight wrote: | Stainless sucks at heat transfer, and has to be welded. | Copper can be soldered (low temperature), or I believe | refrigeration lines are commonly brazed (higher | temperature). | | Material cost doesn't tell the whole story. Stainless is | harder to work with, therefore costs more to manufacture. | And even if it ended up being less expensive in the long | run, there would a lot of capital equipment to recover. | [deleted] | jasonwatkinspdx wrote: | FWIW there does seem to be a certain blind spot about PEX | as an alternative in the US. | | A friend redid his whole house with it himself to great | success. He mentioned one of the contractors he got a bid | from while deciding his plan, when asked about PEX, said | "Well that just saves you time and money" in tone of | dismissal. | | I think there's something similar going on with ductless | heat pumps in the US. They're a fantastic option in my | area but still uncommon. Part of that seems to be the | installers make more from other options. | | I very much agree with you about the tendency of HN's | community to assume other industries are simply obvious | idiots, rather than realizing they're just ignorant of | that industry's reality. | FuriouslyAdrift wrote: | Scroll compressors have come down in cost a bunch in the last | few years. There's really very few reasons not to get a heat | pump, now, for new construction. | nightski wrote: | The main reason in my area is that a.) these fancy new | efficient ones aren't available easily and b.) no contractors | in the area to install/service them. I just got a new gas | furnace and really wanted to add a heat pump to the mix but | after several quotes all of them either said no or strongly | avoided the question. I couldn't get a straight answer. | bityard wrote: | Even in areas where natural gas is much cheaper than | electricity? | FriedPickles wrote: | Id love to see a combined heat and power system that burns | natural gas to drive a heat pump compressor, and recovers | the combustion heat. I wonder what multiplier it would get | on a therm. | mindslight wrote: | There are refrigerators that run directly off of propane. | https://www.ferrellgas.com/tank-talk/blog-articles/how- | propa... | | The working temperatures of ammonia are probably wrong | for a heat pump, but perhaps something similar could be | devised. | nanomonkey wrote: | I've been contemplating the same thing. Something like | the WhisperGen stirling engine hot water heater should be | available to everyone. Hell even a water cooled honda | generator that runs off natural gas, and pumps the | radiator fluid into your home for heating purposes would | be nice. It seems weird that we aren't producing | electricity when ever you burn natural gas for heating. | icedistilled wrote: | yes. Because Global warming/climate change is real and | installing new furnaces bakes in decades of additional | natural gas usage. Also, that natural gas price may change. | dgacmu wrote: | A heat pump is likely to have an average efficiency of near | 300% - call it 250 if you want to hedge. A high efficiency | condensing gas furnace gets about 95%. So on a per-watt- | hour basis (equiv., BTUs), your gas must cost less than | roughly 1/3 what your electric costs. | | There are additional savings if your gas furnace is the | only gas appliance in your house and you can remove gas | service entirely, saving the monthly customer fee. | pandaman wrote: | And to get to 250% COP in heating on average you'd expect | to have, at least, 8.5 HSPF2 rating on your heat pump | (it's still just the heating performance w/o de-frosting | cycles as far as I understand so the real world COP of a | 8.5 HSPF2 will be lower than 2.5) | raverbashing wrote: | > The higher pressurizations require more expensive components | and compressors | | Sure, that sounds like an acceptable compromise for those who | need the lower operating temperatures | | And maybe technology can get those compressors at the same | price point of current compressors | jacquesm wrote: | But then current compressors would end up cheaper and a | difference would still exist. | szundi wrote: | Or not produced anymore and prices go up for legacy system | maintenance. Like try to buy 4MB of EDO RAM | jacquesm wrote: | I don't think that will happen. The price difference will | be substantial due to the changes required and volume | will probably not be enough to offset those. | abracadaniel wrote: | Your point should stand, but it did make me discover that | people make new 30pin 4MB simms, which were very | difficult to get for years because they were commonly | used in ATMs and only available used. | londons_explore wrote: | > then the boiling point of the refrigerant must be below -20F | | This isn't the limiting factor for choice of refrigerant... | There is _always_ a low enough pressure that anything boils. | | The problem is that at very low pressures (think a few | millibars), gasses need huge diameter pipes and huge pumps to | move even a small number of kilowatts of heat. | brilee wrote: | Another issue is that at pressures below one atmosphere, the | system will suck in ambient air, causing condensation to | collect inside your refrigeration circuit, which creates ice | crystals, etc... nobody does that. | londons_explore wrote: | Plenty of systems work below atmospheric pressure. For | example, Fridge freezers most commonly use isobutane | (R600a), and when operating with the freezer at -20C, the | pressure will be half an atmosphere (ie. -0.5 bar below | atmospheric). | | The systems are filled using a vacuum pump to ensure there | is very little atmospheric air in them, and they also use a | 'filter dryer', which is a chemical compound chosen to trap | any remaining water and various other common contaminants. | a_square_peg wrote: | We need heat pump that work below -20F like we need an electric | car that can go 1000 miles in a single charge - which is we | really don't for the 99% of the use case. What's needed is a heat | pump that's cheaper to install than gas furnace or oil boiler for | the 80% of the population. On few days of the year when it's -20F | or below, it's ok to use resistive heater as a back up. | loloquwowndueo wrote: | Millions of Canadians would disagree with that assessment. | a_square_peg wrote: | I'm Canadian myself. Heat Pump is actually very popular in | the eastern maritime provinces and is gaining in popularity | elsewhere also. | 2OEH8eoCRo0 wrote: | I think a cheap heat pump and a cheap wood stove for | emergencies would be ideal. Depending on resistive heat can be | dangerous if power goes out. | scojomodena wrote: | Sort of, but really we need both. Yes cheaper for most people. | But as someone who lives in Minnesota, we definitely get below | those temps. By code we require full backup resistive heaters | for a heat pump at such a rating which increases the full cost | and installation cost. Plus, it is much less efficient than a | heat pump (though efficiency lowers as the temp gets colder due | to defrost cycles). | mindslight wrote: | AFAICT one of the main difficulties with heat pumps is that | they want to use low temperature heat emitters, similar to | condensing boilers. This is a general thermodynamic rule, but | hits sources aiming for high efficiency extra hard, since | they've been designed around exploiting it. | | So you can't just take a decades old system with oil/gas using | finned radiators, just replace the boiler, and have it supply | enough heat on the coldest day ("design day"). Rather you'd at | least need to add some additional emitters, greatly increasing | the scope of the project for a professional installer. | | What I haven't been able to find an answer to is that everybody | says hydronic heat pumps need low delta T of 5-10 degree F | (implying high flow rate for given heat transfer). But I would | think the real constraint would be just on their leaving water | temperature, and a heat pump (load side) that took in 100F and | put out 120F (at say 5GPM) would be happier and more efficient | than one that took in 110F and put out 120F (at 10GPM). But | I've yet to find anything that confirms this. | sokoloff wrote: | Your intuition is correct on the last point. Where the | "everybody says" side is coming from is the _average water | temperature_ in the emitters (and therefore heat flux from | emitters to the building) will be higher if the flow (supply) | is 120degF and return is 110degF than if the flow is 120degF | and return is 100degF. | | That's why designers are often specifying lower delta-Ts for | low-temperature emitters: to allow the flow temperatures to | remain as low as possible [for efficiency] at a given average | water temperature [for effective heating]. | mindslight wrote: | It's definitely in line with general thermodynamics. One | would expect lower entering water temperature to be more | efficient (especially with the condenser being | counterflow). I'm just not sure if there's something | specific about the design of real world heat pumps that | makes it so that higher delta T across the pump is | problematic. I thought I would have come across some | hydronic professional explaining this a bit more in depth | while focusing on each variable, but so far I have not. | | Maybe it never comes up in practice because heat pump | systems inevitably need some kind of buffer tank. If you're | designing a system from scratch then you design for lower | delta-T in the emitters to keep the max water temperature | down. And if you're using existing emitters then you just | live with the inefficiency due to higher max water temp, | but still keep the flow from the heat pump to buffer tank | high regardless (to keep the max water temp from being even | higher). | a9h74j wrote: | There is a YT video with Matt Risinger | discussing/promoting "Thermafloor"(IIRC) which uses 25mil | aluminum over the full surface of the flooring panels. | They discuss some of the benefits of lower water | temperature, but not all of the variables. | amluto wrote: | > What I haven't been able to find an answer to is that | everybody says heat pumps need low delta T of 5-10 degree F | (implying high flow rate for given heat transfer) | | I don't see why this would matter at all. Maybe the heat | exchanger would need to be sized differently for a different | flow rate, but in general a lower entering water temperature | on the hot side seems preferable. | [deleted] | sigmar wrote: | I'm not an expert on the topic, but I imagine that a heat pump | that can handle -20F is also much more energy efficient when | the temp is 0F (in comparison to a heat pump that was rated | only for -5F, operating at 0F). | Someone1234 wrote: | Isn't the primary issue not the cost of installation, but | rather the cost of the fuel? Natural gas in most of the US is | far cheaper than electricity, and even if heat pumps are | theoretically more efficient than natural gas (energy in:heat | out), if the fuel is two or three times cheaper none of that | matters. | onlyrealcuzzo wrote: | In most places in the US, in normal working conditions, Heat | Pumps are 30%+ cheaper than a gas furnace to run. | | However, in some really cold places like Chicago, | Minneapolis, etc - the days where current heat pumps are | inefficient might be enough to make it cheaper to always run | gas. | | OP is proposing to have both systems and only run the gas | furnace on extreme days - which would lead to a ~30% | reduction in running costs. | | I suspect the CapEx of having two heaters wouldn't make | sense, though. | | It'd be better to just have a hear pump that can run | efficiently at colder temps. | mrep wrote: | You generally have an air conditioner though as well as a | furnace and you can get those that can also work as a heat | pump. Mine supposedly works as both but they only set it up | for cooling and my gas furnace does all the heating :( | [deleted] | Scoundreller wrote: | I think it's the opex of 2 grid connections that messes | with the numbers. | | Depends on how your utility charges, but I feel like | many/most sell you the gas roughly "at cost" and then some | fixed monthly delivery/connection charge that covers their | regulated rate of return on their network equity. | | Oil or propane supplemental heat might be cheaper than | Natgas supplemental heat. My money is on wood pellet stoves | for supp heat for those that don't require full automation. | Or maybe even dirty coal... | BobbyJo wrote: | Also, the capex of gas delivery. Not needing infra to | deliver gas to each and every house would likely be a | pretty big win. | Epa095 wrote: | Unless gas is subsidised I don't really understand how gas | can be cheaper. A modern heat pump can give 3-5 kWh of heat | using 1 kWh of electricity. And a modern gas generator is | roughly 50% effecient at creating electricity (according to | the Internet). So by using electric and a heat pump you | should be able to get 1.5-2.5 times more heat from the same | gas by making electricity of it first compared to burning it | directly. | SoftTalker wrote: | Modern residential gas furnace is 90% or more efficient. | Epa095 wrote: | Makes sense (I would have guessed closer to 99% | actually). But 99% is still less than both 150% and | 250%:-P | happyopossum wrote: | You seem to assume that energy cost is the same no matter | how it's delivered. Here in California, electricity is | much more expensive than natural gas for the same amount | of potential energy. | Epa095 wrote: | Yeah delivery cost might be a factor, maybe it costs more | to deliver 1 kWh of electricity through a wire than (the | equivalent of) 1 kWh of gas with a truck (that's what you | use right?). Gas, if its stored in a big tank under your | house, also had the advantage of beeing "locally cached", | so you don't have to dimension the system for the max | load in the same way. | maxerickson wrote: | Many urbanized areas in the US have natural gas | distribution pipelines. | | Rural areas rely on propane delivery, which is roughly 2x | the cost of the piped natural gas (per unit of energy). | bluGill wrote: | What is the efficiency of the power generation system? | The whole system costs matter not just the individual | HVAC unit | chordalkeyboard wrote: | > A modern heat pump can give 3-5 kWh of heat using 1 kWh | of electricity. | | At lower temperatures the modern heat pumps cannot attain | this COP, which is why they are working on heat pumps that | work at lower temperatures. | njarboe wrote: | At least in the US, electricity rates and natural gas | prices are highly regulated for retail customers. Thus the | wholesale price of gas does not generally correlate to the | retail price of electricity. In places like California | electricity prices are very high due to renewable | generation requirements. You would definitely want to have | your own solar installation before converting over to all | electricity in that state. | DoneWithAllThat wrote: | We're being forced to. After 2030 no more gas water | heaters or furnaces can be sold. The cost of heating your | house and water here is going to probably triple or more, | and will fail every time there's a blackout. | Scoundreller wrote: | Maybe the gas is cheap, but the monthly and up-front | connection costs mess with the economics. | | And that cost will only go up as people cut the gas cord. | | Depends on how your utility bills out it's infrastructure: | some charge minimal monthly connection fees, others a lot. | | I honestly wouldn't want to own a residential-focussed gas | distribution company unless someone revolutionizes stirling | engines or micro cogen systems and people start cutting their | electric cord. | lizknope wrote: | I live in a pretty standard suburban subdivision in the US. | All the houses are 25 years old. I have about 60 coworkers | in very similar situations. I think everyone of us has | natural gas that was installed when the original company | built all the homes in the subdivision over the course of a | year. Stuff gets a lot cheaper when everything is put into | the ground at the same time. My monthly gas connection fee | is $10 so that in the summer my bill is around $19 which is | $9 for the water heater and $10 for the connection fee. | kube-system wrote: | The thing with heat pumps is that they can be as much as 300% | efficient (effectively) or more. This is because they can get | "free" heat from the environment. | | So even if per unit of energy gas is way cheaper, heat pumps | can _still_ come out ahead. | anikom15 wrote: | This is true when it's warm enough outside that you don't | need the heat pump anyway. When the temperature becomes | cold, it's a different story. | | Heat pumps might make sense when you have a well-insulated | house, like the kinds in Northern Europe, to trap heat and | reduce the power required to heat the room. American houses | in most places are far too drafty. | dragonwriter wrote: | > Heat pumps might make sense when you have a well- | insulated house, like the kinds in Northern Europe, to | trap heat and reduce the power required to heat the room. | American houses in most places are far too drafty. | | If you need significant heating _or_ cooling in a home, | the first thing you need is to deal with is insulation, | otherwise nothing you do is going to work well. | anikom15 wrote: | That's true, but unless you are doing some kind of | industrial work (including running very hot computers), | you shouldn't need significant heating or cooling in most | of America. | | The idea that indoors needs to be between 72deg (F) and | 75deg at all times is unsustainable. | | The other problem is that if you _do_ decide to insulate | the house, then you may end up needing to use A /C | because the house can no longer be wind-cooled to an | acceptable temperature, and you will need to update the | heating system as traditional methods of heating | (fireplace, stove, simple furnaces) depend on external | air circulation. | dragonwriter wrote: | > That's true, but unless you are doing some kind of | industrial work (including running very hot computers), | you shouldn't need significant heating or cooling in most | of America. | | > The idea that indoors needs to be between 72deg (F) and | 75deg at all times is unsustainable. | | The WHO recommends a general minimum household | temperature of 64degF for all populations for health | reasons, with a higher minimum for sensitive groups | including children and the elderly; maximums are more | regionally variant because acclimitization (which takes | years) plays more of a factor in high-heat health risks, | but even in extreme regions seems to top out at about | 90degF for the general population. | | Lots of the US spends lots of time significantly out of | at least one end of that range (and, especially given | that the top gets lower in colder regions, lots of the US | spends lots of time significantly out on both ends of the | scale.) | | > The other problem is that if you do decide to insulate | the house, then you may end up needing to use A/C because | the house can no longer be wind-cooled to an acceptable | temperature | | If you have a house that is insulated well _and also_ | lacks doors and windows that can be opened, sure. | | But... that presents other problems, too. | Epa095 wrote: | Modern heat pumps can be up to 500% efficient (using 1kWh | of energy gives 5 kWh of heat) at optimal temperature. | kube-system wrote: | Yes, I went with "300 or more" because that's a more | typical number for a run-of-the-mill unit. | a9h74j wrote: | And even the low-temperature-capable heat pumps reduce | toward 100% at the low temperature end, IIRC. | mikeyouse wrote: | Yep, here's a spec sheet for a unit I'm looking at as a | drop-in ducted replacement for my existing system -- it | has all of the models listed, but I'm looking at the | 4-ton unit (12k btu per ton, so 4-ton = 48k BTU, hence | the MDU180 _48_ ): https://mrcool.com/wp- | content/dox_repo/mc-uni-perf-ss-en-01.... | | It takes 7kw at 17oF to provide 48k BTU. There are | 0.293W/hr per BTU so 7,000W = 25k BTU "in" and 48k BTU | "out" or a COP of 1.9. At -15oF, it's using 5.9KW but can | only produce 28,500. So a COP of ~1.4. Still better than | electric resistive heating but not by much. At 40oF, the | COP is more like 3.3 which is in line with the very | efficient numbers. | | Fortunately my 99% design temp is ~8oF and my area only | sees 20hrs below zero per year, so this will work just | fine for me. | a_square_peg wrote: | Interesting thing here is that natural gas is about 1/3 the | cost of electricity per energy unit, so when the COP is above | 3, it's cheaper to heat home using heat pump. | | The reason why natural gas is about 1/3 of the cost of | electriciy is because most natural gas power plants run at | thermal efficiency of about 30%. | pfdietz wrote: | Combined cycle natural gas plants have an efficiency of | about 60% (lower heating value). Even simple cycle NG | plants are about 40% efficient (again LHV). | doikor wrote: | Yup. And at least here in Finland the pumps come with the | resistive heater included so it automatically switches over to | it once it gets too cold. | | Which where most people live here averages to less then 1 day | per year so not a big deal. | | Way bigger issue here is some fall storm destroying the power | lines and being without electricity for multiple days when it | already is cold enough they one needs heating. | kube-system wrote: | That's an issue even with gas furnaces here in the US, as | they won't run without electricity. | dahfizz wrote: | True, but furnaces have a much lower power draw. They are | easy to run off a generator, which are common in areas that | frequently lose power. | jacamera wrote: | Yes but it only requires a couple hundred watts to power | the blower motor and electronics of a gas furnace. They're | easy to power off of a small portable generator or even a | cheap inverter hooked up to your car. The same cannot be | said of a heat pump or resistive heater. | kube-system wrote: | They are, and I have a contingency plan for this myself, | but few people have the tools and knowledge required to | accomplish this. | AuryGlenz wrote: | Eh, for the first time I got an alert message on my cell phone | asking people to reduce their electricity usage during a | blizzard here in rural Minnesota. | | If everyone is suddenly using electric heat when it's -20 in an | area there might be load issues. | mirrorlake wrote: | The number of electric devices added to the grid is likely a | predictable percent increase every day/month/year, and | likewise, the acceleration of that change is probably | somewhat predictable, too. | | This is not to say we shouldn't be concerned, but denying | yourself the most energy efficient technologies available | (EVs, heat pumps, etc) because you're afraid of power outages | 5-10 years from now seems like overkill. | bowow wrote: | If everyone uses resistive heat during that 1% of the time that | it's -20F or below, the electric grid goes down and then no one | gets heat. Consider what just happened in the southeast with | TVA and rolling blackouts. That was precisely because it was | too cold for heat pumps and so everyone's resistive heat | engaged at the same time. I don't think your EV range | comparison is a particularly good one. You can control your | stops on a road trip, you can't control when it's colder than | -20F outside. | ledauphin wrote: | If they can manage the grid granularly enough and isolate | critical environments like hospitals, nursing homes, etc., I | really don't see a good reason for us to overbuild to handle | the third standard deviation of electricity demand. It makes | a lot more sense to set the expectation that on the coldest | days of the year, your house may spend a few hours | disconnected from the grid in order to shed load. Not only | does the avoid overbuilding, but it also contributes to less | overall fragility in society, because black swan events that | happen once every 50 or 100 years are the sorts of things we | can't build for anyway, so it's better if people are prepared | to endure the unexpected from time to time anyway. | yosito wrote: | Meanwhile, most people in the US don't even know what a "heat | pump" is, and think that "air conditioners" are inherently | wasteful and bad for the environment. | Scoundreller wrote: | It is kinda a concern with heat pump rollouts in Europe: now | that people that didn't have air conditioning before will have | it and will adopt it. | | Having said that, too much of my EU family still thinks air | conditioning makes you sick... and a lot of the latest germ | theory (aerosol transmission or respiratory viruses) is | confirming they might be right. Ugh. At least the rental cars | usually have AC nowadays. | newZWhoDis wrote: | That's absurd, AC doesn't "make you sick". What basis could | anyone have for such a claim? | SoftTalker wrote: | AC evaporators and condensate pans can breed bacteria and | mold. At best this can be smelly, at worst it can make you | seriously sick. See the history of Legionnaires disease. | nottorp wrote: | If you have individual room split units you just clean | them yearly or so. Just open the interior unit and spray | it with the cleaning solution. Smells nice too :) | | Whole house a/c systems like the US has are an entirely | different matter... don't know how you clean all those | ducts. | anikom15 wrote: | I've never seen anyone clean their A/C system. | nottorp wrote: | Put "air conditioning cleaning spray" in Amazon. You open | the plastic cover of the indoor part and spray the | internal radiator. | | There's stuff for cars too. | jupp0r wrote: | You need to maintain these systems. Otherwise | refrigerators, sinks and toilets also make you sick. | Scoundreller wrote: | There are hazards to recirculating air (instead of opening | a window), e.g. aerosol viruses, off-gasing and some of | these people smoke like chimneys. | pitaj wrote: | It was down to -8F (not including wind chill) a couple days ago | here. I have a small, old house but I'm considering replacing the | old system I have now with a heat pump. | | My concern is two-fold: | | - my house is not well air sealed | | - my house is not well insulated | | So I worry that I'll need an extremely oversized heat pump in | order to have enough capacacity for the coldest days. | | I suppose having a backup heating source would prevent needing | such a large unit. Plus it would provide some amount of | redundancy of the heat pump were to fail in the winter. | | The question then is, should I use electric backup heat, or stick | with my existing gas connection? Electric is simpler and there's | no exhaust fumes or CO risk to worry about, but gas is still | cheaper here I think. | Scoundreller wrote: | What are your no-use natural gas costs like? Might make a wood | stove, oil, wood pellets or maybe even propane cheaper. And | then you're not depending on two grids for standby/supplemental | heat. | coryrc wrote: | The best ROI is to insulate and air seal. | hn_go_brrrrr wrote: | And if you can only do one, air sealing is almost always | preferable. | jebarker wrote: | We live in the Colorado Front Range in a 50 year old house that | isn't particularly well insulated. We have a Mitsubishi high- | efficiency air source heat pump distributing air through our | existing duct work. We have electric backup inside the air | handler. Last week it got down to -15F overnight. The heat pump | ran throughout and there was only really activity from the | electric backup during the occasional defrost cycle. We keep | our house pretty warm too as we have a baby. | | In winter the heat pump seems to have no issues meeting our | heating needs albeit at quite a bit higher overall utility cost | compared to our old gas furnace. In summer the heat pump is | much more efficient than our old AC unit and our solar panels | cover >100% of our usage from ~April-Oct. | | Prior to installing the heat pump we did as much insulating as | we could (mostly attic) and I think that was important for | enabling the heat pump to keep up in the cold. The nature of | the heating is lower level and continuous compared to the | occasional blasting from a gas furnace, so you do want to | prevent rapid leakage of heat from the house. | sokoloff wrote: | My 2 cents: Find your local "design heating temperature" and | then determine your tolerance for the house falling a few | degrees below the setpoint during the 1% of hours that the | outside temperature will be below that. Most people would be | fine if their house fell to 67degF or 68degF for a few hours, | especially since some of those hours are bound to be at night | (where other people are setting their stats back to those | levels anyway and you might well be asleep and never notice). | | If you have no other gas appliances and generally reliable | electric supply, I'd be inclined towards going with electric | backup. That avoids the $10-15/month gas meter charge, which | pays for a fair amount of the more costly electric heat. If you | have other gas appliances and cheap [at least for now] natural | gas supply, going with a natural gas backup allows you to use | the cheaper source of heat for both backup and/or in case | electricity rates go up substantially versus gas. | | CO risk is minimal and you should have a line-powered CO meter | in the mechanical room and some CO meter on each level of the | house anyway. | Scoundreller wrote: | > have a line-powered CO meter | | Thank you for stating this. If your furnace requires | electricity to run, you don't need a battery-powered or | battery backup CO meter. Unless you have a wood stove or | light fires indoors when it gets chilly. Otherwise you're | just wasting batteries. | r0m4n0 wrote: | I'm in a very similar predicament but the temperature where I'm | at only go down to the 30s-40s mostly during the winter. I get | some rebates where I'm at to replace a furnace so that brings | replacement costs to be about equal between furnace and heat | pump. I don't have solar, kw per hour costs are around 13 | cents. My AC is non op needing to be replaced (it regularly | gets into the 100s for months on end) and my furnace is | functioning at 25 years old and no problems, although when it | turns on it sounds like a small bomb exploding in my ducts. I | have 50% of my house with extremely drafty single pane windows, | the other 50% have been replaced. House was made in the 1930s | out of brick and appears to be well insulated otherwise though. | | I am afraid that my overall utility expenses will go up | drastically with a heat pump though. Can a heat pump even keep | up with a house that loses heat like crazy out of the windows? | I seem to get contradicting information from the salespeople, | the internet, etc. if anyone has any anecdotal info it would be | greatly appreciated | Qwertious wrote: | If your main heat problem is the single-pane windows, perhaps | you could use the bubble-wrap trick? | | https://www.builditsolar.com/Projects/Conservation/bubblewra. | .. | cbrozefsky wrote: | Others have said it, but it bears repeating. Do the air sealing | and then insulation ASAP. It increases comfort and the ROI is | way higher than moving to a heat pump. | | I started with my old Vermont home with minimal insulation, | single pane metal frame windows that would ice up, and drafts | everywhere. After our first winter, we had the local efficiency | program recommend a contractor who came out and measured air | exchange and identified the order of work. New windows, sealing | attic, re-insulating attic. We got a considerable tax credit | for the work, and the comfort improvement was astounding. | | Just this last summer we made the jump to mini-split heat | pumps. They are working well, but I doubt that would be the | case without the air sealing. We keep them set at their lowest, | 61F, and supplement with a wood stove in the living room, maybe | burning 2 cords a year. | | As an aside, this is our first winter, and our bill for | December was 300 dollars, at $0.18/kWh. That's about 25% lower | than our estimated oil charges last year for the same period. | However, this year oil is ~$4.6, almost 50% higher, so that | hedge against fossil fuel price is really paying off. Add in | the AC comfort that is largely offset by our solar array, and | they are a worthy investment (oh, and 0% financing). | | None of this would be working without that critical investment | in air sealing and insulation. | pinkorchid wrote: | It may be worth insulating it first. It cost me just about | $1500 to go from effectively no attic insulation to R60 for a | thousand sq ft, and besides making a massive difference in | comfort it reduced energy usage by about 50%. | hooverd wrote: | How expensive would it be to run source water to an entire | neighborhood for heating and cooling? Have one heating/cooling | plant and per building heat pumps. | projectazorian wrote: | This is called district heating and is not uncommon, some | cities in the US have it (it's used in Manhattan for example) | but it's more popular in Europe and Asia, especially in | Scandinavia and former socialist countries. | | https://en.wikipedia.org/wiki/District_heating | hooverd wrote: | Lots of colleges have steam tunnels too. With individual heat | pumps you probably lose some efficiency but the source | doesn't have to get as hot or as cold. Doing a residential | retrofit sounds like herding cats but in somewhere like | Phoenix or Tucson the efficiency gains might be worth it. | mlsu wrote: | This is frequently done when you have a (very hot) boiler in a | power plant or chemical process nearby. A natural gas turbine | can't generate electricity very efficiently on even 212f steam, | so instead of building some gigantic turbine to get that last | bit out, you route the waste heat into a nearby neighborhood. | PreInternet01 wrote: | Having heat pumps that can operate during arctic freezes is of | course, and pardon my pun, pretty cool, but I wonder which | percentage of the consumer market actually requires this? | Especially keeping in mind that your pump not actively heating | its internal storage for a few hours every day is not a huge | issue: it only becomes problematic when the external heat | exchange is unavailable for 6-8 hours or so. | | Another comment in the article, regarding electricity grid | impacts during peak demand periods, is more interesting to me. | Currently, there is no mechanism whatsoever for heat pumps to | automatically shift their grid draw (or re-delivery) to certain | time slots, and/or to coordinate those slots with other units | nearby. Both of these would greatly help to balance the grid, but | won't be available until standardization gets off the ground and | expensive retrofits are done. That's a shame, really... | eternityforest wrote: | It's usually about 35F to 22F daytime when I turn on the | heater, so efficiency at low temperatures would be the main | thing that matters. It doesn't get to -20F that often most | years, but it does hover around -5F for days at a time on | occasion. | | Current generation heat pumps are probably still worth it but | ultra low temp performance would be nice. | therealcamino wrote: | There may be no existing, comprehensive central management of | electrical demand from heat pumps but that doesn't mean there | are no mechanisms whatsoever, because there are systems already | for regulating AC demand. In our region of the US, residential | customers can opt in to a system where the electric utility can | remotely disable their air conditioning compressor during times | of peak load, in exchange for discounts. There are agreements | on how long that can remain in effect, which would probably | have to be stricter for heating systems, and probably have | other safeguards added. There are also non-centralized AC | mechanisms through Nest thermostats, where they can pre-cool | buildings early in the morning to spread load out more evenly | during the day. | rainsford wrote: | Maybe just as important, whether or not there is a | centralized mechanism for dealing with it, utilities already | have exactly the same load problem with AC in the summer and | have more or less figured out how to deal with that. It may | be different in places where AC is less widespread, but in | most of the US I wouldn't expect heat pump load issues to be | much of a problem in the winter. | bluGill wrote: | Winter is worse than summer, because Delta-t is much | bigger. 130f to 70f is 60 degree difference, while -30f to | 70f is 100 degrees difference. | altacc wrote: | There's quite a big market for this, such as a lot of the | Nordics, where -15C for a few days is common enough that not | having heating then would rapidly become an issue as homes | freeze quickly. At those temperatures you have heating on 24/7 | to keep the cold at bay. Electricity costs on those cold days | are indeed high due to the constant demand of heating. | rektide wrote: | House heating tends to have controls from thermostats or other | devices; I'd tend to look to them for grid-related time- | shifting. | | I did run across a release on a new generation of a heat-pump | hot-water heater, which does seem to have some kind of grid- | shifting built in. A. O. Smith's Voltex AL, | https://cleantechnica.com/2022/12/21/all-i-want-for-christma... | PreInternet01 wrote: | > House heating tends to have controls from thermostats or | other devices; I'd tend to look to them for grid-related | time-shifting | | Not for heat pumps. In a typical configuration (large heat | reservoirs combined with under-floor heating in a well- | insulated house), temperature-setpoint changes take 12-24 | hours to propagate. | | So, governing the (in-room) target temperature settings is | unreliable/unpredictable. Whereas the in-pump storage | temperature is a whole lot more manageable. | | The old advice "turn your thermostat down at night" therefore | also doesn't apply to most heat pump installations -- in | fact, it might be disadvantageous. "Select the average | temperature you need and don't touch it" is much better | advice. Need localized heat/cold? Use another solution for | that... | a9h74j wrote: | > don't touch it" is much better advice | | Saw one heat pump controller discussed which had a curve | set for demand vs outside temperature, and the "thermostat" | was to set a delta relative to this. | mindslight wrote: | The standard large buffer tank is 120 gallons, which stores | about 20kBTU at 20F dT. So to last 4 hours you'd need your | design heating load to be 5kBTU/hr, which I think is out of the | realm of even new construction. | | You could raise the max water temp and install a few tanks to | get in the ballpark, but that's an assumption that most systems | won't have. Also I wouldn't be surprised if "operates down to | -20F" includes reduced efficiency/output that already relies on | the buffer/storage to compensate for. | agentwiggles wrote: | My Senville mini split claims to work at temps down to -22F. | During this recent winter storm, temps got down to about -10 | where I am, and it managed to keep my garage around 50F. Nowhere | near comfortable, but pretty damn impressive to be able to keep | my relatively poorly insulated garage 60 degrees above the | weather. | | I was quite happy that this storm occurred while I was in | Christmas PTO, since my garage is my office. I could have made it | workable with a supplemental space heater but it was nice not to | have to! | therusskiy wrote: | I am lost. | | Are heat pumps the same thing as split air conditioners that can | heat air? | zip1234 wrote: | A mini split is usually a heat pump system although some of | them use resistive heating. They have been getting much better | in recent years. | Qwertious wrote: | Heat pumps are also known as "reverse cycle air-conditioners". | downvotetruth wrote: | outside source(d) heater | [deleted] | ARandumGuy wrote: | Air conditioners are heat pumps. They move thermal energy from | the inside to the outside to cool a space. | | In this context, a heat pump refers to the same type of system, | but in reverse. Instead of moving thermal energy from inside to | outside, you're moving that energy from outside to inside. This | can work even when it's cold out, because cold outside air | still has a lot of thermal energy that can be moved. | | The main benefits of heat pumps for heating are twofold: | | 1) It's significantly more efficient then electric resistive | heat, because heat isn't being generated, simply moved around. | 2) Heat pump systems can be configured to work to both heat and | cool a space. There are very few changes needed to make this | happen, meaning that if you need AC, you might as well get a | heat pump to do both jobs. | throw0101c wrote: | -22F / -30C capable heat pumps already exist, e.g.: | | * https://www.spacepak.com/solstice-inverter-extreme | Scoundreller wrote: | I think the ultimate combo will be heat pumps + wood pellet stove | as supplemental heat. | | Then you can cutoff the gas grid connection and its associated | standby/account/blah blah charges. It's a big sunk cost in a lot | of places that messes with the economics of switching to heat | pump as primary heat. | | Pellet stoves are semi-automated. Around 90% efficient. If you | already have central heat pumps, you can install one and let your | HVAC circulate the heat around. Can stockpile as much fuel as you | want. Cheaper than oil or propane and not much more expensive | than firewood once accounting for improved burn efficiency. Just | need to empty the ash gray once a week or so, and dump a nice | smelling bag in for every ~24h of operation. | | Relatively straightforward install: just need a wall to punch | through and a standard power outlet. Minimal clearance | requirements. Fun to watch the fire tornado. | | Big downside is they need some electricity (mainly for for the | powered vent). Hit or miss when it comes to insurance companies | that think explosive gas systems or high current electric devices | are safer. | 2OEH8eoCRo0 wrote: | Pellet stoves require electricity to run the auger. Also- | nobody gives away free pellets but it's pretty easy to come by | free wood people are giving away. | inthepipe wrote: | Gas heaters also have around 90% efficiency, I think. It seems | like gas is strictly better? | Scoundreller wrote: | Depends on your constraints. The CO2 round trip is a lot | longer for gas. | sandworm101 wrote: | Cool. But it hit -39c in my area a couple weeks ago. They still | have some way to go. | Qwertious wrote: | If you run copper tubing underneath the frost line, a heat pump | can still run at that temperature. Problem is, that's a whole | lot of expensive construction for relatively minor energy | savings. I hear they're doing it in Alaska, where it's used | much more frequently once it's installed. | svdr wrote: | A nice explanation of the working of heat pumps from Technology | Connections: https://www.youtube.com/watch?v=7J52mDjZzto | a9h74j wrote: | Great channel. Doesn't he lament that US installers are still | charging "don't bother me" enormous premiums on heat-pump | installs? ___________________________________________________________________ (page generated 2022-12-28 23:01 UTC)