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My heat pump: a personal story about a broken heating industry
- Kon-Peki 3y ago> but because my installer looked at the data, it needed no major new pipework How about if we start with this? What data, and how do you collect it? The site links to [1] which looks like it has some great info. But any potential adoptee will still need to translate that into some actionable steps to gather the data needed to know how to size the heat pump system
- GordonS 3y agoI too was a bit disappointed that the data in question wasn't explained. The only thing the article has made me do, is become even more wary about heatpumps!
- Kon-Peki 3y agoI don't get the impression that I should be more wary about heat pumps, but that if I have the data collected in advance I would be ready to switch when the time comes. Armed with that data, you could also do some advanced prep work so that you can purchase a smaller system that will still maintain high levels of comfort. And any prep work would likely improve the performance of the existing system you have.
- GordonS 3y agoRight... but what data? What am I looking for?
- sokoloff 3y agoAdjust the boiler so that the output flow temperature is 55°C (or 130°F) or lower. See if your house remains comfortable on the coldest day you expect to have. Note that if you have a boiler not designed to operate with condensing flue gases, this test will eventually damage the boiler [over the course of months, not hours]. If you have a plastic exhaust pipe on your current boiler, you're totally fine to do this. More writeup here: https://news.ycombinator.com/item?id=39144329 https://news.ycombinator.com/item?id=39144329
- Kon-Peki 3y agoI do appreciate the writeup, but I feel as though there has to be a better way :) In my area, the most common HVAC system is going to be a gas-fired forced-air furnace along with a central air conditioning system. What do you do there?
- sokoloff 3y agoAir to air heat pumps are a pretty straightforward retrofit there. (Including central units with reversing capability; heat pumps don’t have to be per-room minis.) In some ways, that style of central heat pump is less talked about because it’s usually a straightforward replacement. Ducts may need to be enlarged in heating-dominated climates though.
- fireflash38 3y ago1. Heating Degree Days 2. Net heat delivered (BTU delivered * efficiency) 3. Calculate BTU used per heating degree day 4. Calculate your heat load (BTU/hour) 5. Multiply by the ASHRAE sizing factor (1.4). That's enough to allow you to size/resize a gas/oil furnace, as well as see what sort of costs you'll run. To compare directly to a heat pump is difficult, as you also need to pull in your electricity cost, gas/oil cost, and if you have demand pricing, what sort of temp you keep your house at. I will say though, going from something like a 9 SEER AC/heatpump to 17 is huge. 17 -> 20? Not so much.
- sokoloff 3y agoYour last point is excellent, especially if you have a modulating/condensing boiler. (Do you have plastic exhaust piping and a small plastic line that drips water from time to time when the boiler is in operation? You do.) The lower you can make the return water temperature, the more efficient your condensing boiler will run. The way to do that is to lower the leaving water temperature (and accept/relish the corresponding longer run times). With my outdoor reset properly tuned, my Nest thermostat will run 22+ hours of every day and sometimes 24 out of 24. The outdoor reset control is the primary temperature control on the house and the thermostat serves more as a limiter than as a control. This has the effect of using the lowest possible water temperatures (most efficient), which ends up being the most comfortable for the occupants because there's very little overheat/shutoff/overcool/turn-on cycling.
- sokoloff 3y agoWhen I was trying to determine whether an air-source heat-pump could work to replace my old (like 1950s old) gas boiler, what I did was reduce the flow temperatures leaving that old boiler to see what flow temperatures would be required to satisfy the heat loss at various outside temperatures. (This is basically discovering the required outdoor reset curve on a mod-con boiler.) I found the minimum temperature to maintain 71°F at various outside air temperatures and then looked to see whether the ASHP could provide that flow temp (sometimes called "leaving water temp"). (This is also what the article's author did.) In a case like that, I'm inherently proving that the pipes are sufficiently sized as well. Now, the downside is that it requires time and effort on the homeowner's part, requires a working old boiler, requires a winter season of variable temps, so it's not a practical way for a contractor to bid the job, but for HN readers, you can do it that way. (Note also that if your old boiler is not a condensing boiler, you will be damaging it by causing it to condense acidic water from the exhaust. I was OK with that, because I knew it was going to be replaced the following year.) If I found that the house struggled to maintain temp, that method doesn't tell me whether increasing the pipe size would help (though having a larger than desired delta-T coupled with a low flow rate is a strong hint). For a contractor bidding/design situation, there is a universal hydronics formula which is BTU/hr = 500 * delta-T (in °F) * gallons/minute. Pick the delta-T (often 20°F) and the heat load, and solve for gallons/minute. Look up pipe sizing tables for maximum velocity, then using the pipe size and total developed length, figure out the pump you'll need. Then check the emitter sizing to ensure that it can emit the heat required (to "cause" the delta T) at the lower flow temperatures characteristic of an efficient heat pump system. Ultimately, I proved to myself that a heat pump could work down to an outside air temp of about 18°F [which is slightly above our 99th percentile design temp] with flow temps of 135°F, so an air source heat pump could work with slightly reduced comfort on about 2% of days or could work all the time with supplementation with a 9kW [30K BTU/hr] electric boiler. What killed the project is no heat pump installer was interested in doing the work (as reflected by outright declining to bid, while bidding a 4-hour gas boiler swap, or by bidding so high that they might as well not have bid, while also cheerfully bidding a 4-hour gas boiler swap). So my house still burns gas for heat, which matches the author's experience: > this speaks to the third lesson in my story. The boiler market is focused on cheap and quick installation.
- bitshiftfaced 3y agoDoes anyone else find it interesting how overrepresented the topic of heat pumps are on hacker news lately?
- voisin 3y agoThey operate at up to 400% efficiency and represent serious low hanging fruit for household carbon footprint reduction and the main barrier is education, so no I don’t think they are overrepresented.
- zabzonk 3y ago400% compared with what? and how?
- AndrewDucker 3y agoThey can shift 4x the amount of heat than the same amount of energy would generate.
- jdlshore 3y agoA resistive electric heater converts 100% of its energy to heat, by essentially wasting it. A natural gas heater converts about 95% of its energy to heat, by burning it. A heat pump converts about 3x its energy to heat, by acting as a sort of reverse air conditioner that’s cold on the outside and warm on the inside.
- thaumasiotes 3y ago400% is probably the ratio of thermal energy released by the heat pump to energy (of whatever kind) used to operate the pump.
- baking 3y agoThat has to depend on the outside temperature.
- Sytten 3y agoThe author doesn't mention brands but I found that the majority of the cost difference was due to it. I got two Daikin installed and it costed me 15k$ CAD. Simiilar models in Chinese brands run at half that price. Mine also run at 100% efficiency at -15C where most just run 100% at -5C. If you want -25C ones they become much more expansive though. I got quotes from 4 vendors. None were technical enough for my liking they all just told bullshit marketing stuff. One tech did a better job and convinced me, but I still think like the author that they don't really understand the science behind all of it. But this is nof the only industry, I DIY renovated my whole house and I can tell you everything is over the top these days. Another quick example is electricians still wire light circuits like in the incandescent days (max 8-12 bulbs per circuit) where bow LED consumme a fraction of it.
- throwaway402739 3y agoIf you’re talking about residential wiring, most electricians will (in my opinion) correctly wire rooms to breakers rather than device types. It is infuriating to discover that every light on a story is on the same circuit when you want to replace a fixture at night. For dedicated lighting circuits in the USA, the good news is that the 2023 NEC has provisions for 10 amp / 16 gauge circuits in recognition of efficient LED lighting.
- baking 3y agoI think the reason lights are on a separate circuit is that you don't want the lights to go out when a circuit breaker trips. That may be in the code, but I'm not sure.
- Auracle 3y agoBoy, how I wish my breakers were that nicely organized. They’re, at best, regions of my house. Every time I need to do some electrical work it’s a complete guessing game.
- Turing_Machine 3y agoIt's worth taking the time to flip the breakers one at a time, then go around and test outlets so you can write the information down. Good activity for a slow weekend afternoon when you're not under time pressure for another project, and while it's daylight and not unbearably hot or cold. :-)
- bilsbie 3y agoI’d love for someone to make a portable standalone heat pump for a swimming pool. Why not make it solar powered with fold out panels. With 400% efficiency 1500 watts of solar power could get you 6000 watts of heating.
- Workaccount2 3y agoEven better, have the cooling end of the pump be in your house. Cool your house while heating your pool
- throwaway402739 3y agoThere are existing systems today that do this for residential pools. It’s not uncommon for efficient commercial buildings like corporate headquarters to have a retention pond be the heat sink for their chillers in the summer. They’re building a pond for aesthetics anyway, so if it’s large enough this can be cost effective vs. digging geothermal wells.
- vidanay 3y agoThere's a hospital near me built about 15 years ago that has a huge (10 acres?) and deep pond for exactly this. If you hadn't seen it being built, it would look just like a normal decorative pond.
- KMag 3y agoBack when I worked at Goldman, I was told that either their HQ or their Jersey City tower over by the Statue of Liberty had a huge water thermal mass in the basement. They took advantage of cheaper electricity at night to use heat pumps to push the thermal mass whichever way they needed it to go for the next day's heating/cooling needs.
- Maxion 3y agoFor heating e.g. a swimming pool a solar heater would be more efficient.
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- bilsbie 3y agoI think we could bring the price of these down tenfold if they were sold like dishwashers and other appliances. Make a building code that has a universal plug and play interface so they can be connected like a washing machine. The costs explode when you have to buy through installers. (Yes, there are lots of reasons they are not plug and play but let’s figure it out!)
- rootsudo 3y agoThey pretty much are plug and play, you just need a 220V recpricial. They even come loaded w/ refigriant, so it is just cut copper, connect, done.
- bilsbie 3y agoEvery time I’ve bought one there’s been three employees at my house for 8-10 hours.
- rootsudo 3y agoI. guaranteee you they were useless. It helps to have another person to mount it if not on the ground, but you can do it yourself. I've installed over 10+ myself. At the same time, since people saying it's difficult and such - I should start selling this as a service :P
- GordonS 3y agoTFA said some homes need new piping, and Ia believe some need new radiators too?
- sokoloff 3y agoLike many things: "it depends". If your current system can heat the house on the design day with 55°C/130°F water, you don't need to change piping or rads. (My house was in this situation as the original system was designed for gravity flow and so was massively oversized for a modern pumped system.) If your house has minimum sizing of baseboard radiators and the design day flow temperature is 82°C/180°F, then you need to update at least the emitters and maybe the piping.
- randombits0 3y agoGeothermal is even better but can be cost prohibitive. Unlike a boiler, geothermal wells don’t “wear out” and with a steady supply of ground heat, are even more energy efficient.
- Angostura 3y agoI don't think your average London terraced house is going to be drilling 100m - 200m deep bore holes.
- the_sleaze9 3y agoYou could run a central line in the street, then connect to it like sewer and pull heat off of it that way. It would be interesting to check the average public water temp as well, as long as the delta is closer than outdoor ambient air it would be more efficient than heat pumps. You could potentially treat public water like some GCHP use water wells.
- vidanay 3y agoJust drill until you hit a Tube line. Plenty of excess heat available there.
- D13Fd 3y agoWe pushed hard for geothermal. But the quotes for the wells we needed were around $40,000-$75,000, and all of the installers seemed highly uncertain and preferred air-based units. So that's what we eventually went with.
- distances 3y agoThat's a wild price. I'm no expert on the topic, but a quick search results in price estimates in Finland for 15k€-25k€, and another source quotes for equipment 5k€-10k€, bore well 4k€-7k€.
- mtlynch 3y agoI've had a heat pump in my home in the US for the past five years, and it's worked pretty well, but one of the things I've found frustrating is that either the pumps or the installers assume you need to run every indoor unit simultaneously. I have a 24,000 BTU outdoor pump and one indoor unit for the first floor and another unit for the master bedroom. After COVID, we started using our second bedroom as an office, so we wanted an additional indoor unit. I knew that a third indoor unit would be beyond the capacity of our outdoor pump, but we would never need to run all three indoor units at once, so I hoped it would work. The installer said that they can't connect a third unit to our outdoor pump. They claimed that the system maxes out at two even if only two need to be on at once. I couldn't tell if it was bad design by the outdoor unit or if the installer just didn't want to sell me a single unit instead of replacing my whole system, but I was disappointed.
- kcb 3y agoThe indoor unit gets directly connected to the outdoor unit for refrigerant, power, and communication. It's likely then that your outdoor unit only had 2 hookups.
- Symbiote 3y ago24,000BTU = 7kW, to save others from the conversion.
- sokoloff 3y agoThere's no thermodynamic reason that it couldn't work the way you want it to, but the physical connections and electronics controls need to be designed to accommodate that, either with direct connections on the outdoor unit or via a 'branch box' that serves as a connection point for both the refrigerant and electronic control circuits. It's most likely that the installer was correct in that the outdoor unit you had maxed at two and did not have a smooth expansion path.
- rootsudo 3y agoReading the comments, and I find it amazing that people really do pay $5000-15,000 USD for a heat pump. They are super expensive in the USA at $2000-4000, but you can DIY in 1 hour. Really. The labor is truly fabricated. In Asia, I've bought more then I could count, and they typically go for $500-700 for 2hp units, inverter, etc. I've debated bringing somme from Thailand or HK to USA because ven the cost in cargo on a plane makes it cheaper. Daikin for example are manufactured in Thailand, and also JP.
- sokoloff 3y agoIt would take me longer than an hour just to install the electrical circuit and disconnect box. Then more than another hour to bore holes in the brick wall, mount lineset covers, and run the lineset. It's not a huge amount of labor and $5K+ for the labor portion is not justified, but if I sat on your sidewalk with a stopwatch and stopped you at 60 minutes, I'm willing to bet a pretty good sum of money that you wouldn't be done.
- Symbiote 3y ago2hp is 1.5kW. That's 5 to 10 times smaller than the units being discussed here. Does the homemade or cheap heat pump have a 300-400% efficiency?
- VBprogrammer 3y agoThis article doesn't mention one of the main points heat pump gurus have been banging on about for ages - temperature compensation. Essentially, the colder it is outside the hotter you run the flow temperatures. You ideally want this setup so that there is very little intervention from an external thermostat, the balance of flow temperature and heat loss can be set such that one perfectly offsets the other. It's the secret sauce which can take the heat pump from expensive toy to practical replacement for gas. The payoff time is still too long but at least it exists!
- mcculley 3y agoI had a similar problem 18 years ago. I had bought a house with a heat pump connected to the water heater. When it failed, I could not find a local technician competent enough in both plumbing and air conditioning who would touch it. I ended up with two discrete systems.
- kkfx 3y agoMy personal experience, new home (construction completed circa 2017): - MANY design errors, some I spot at project stage, I was told they are not errors, it turn out I was right; - sizing is an issue because the climate may vary MUCH. Three years ago today in the morning there was -22℃ today +10℃ to be in comfort we need to been able to heat (or cool) in much above/below the average cases, so well... I'm not much against pay for extra margins; - my sanitary hot water heater (Daikin/Rotex M2O EKHHP) break after 5 years, a leak from the sanitary water pipe heat-exchanger, two month for a fix, BUT being provident I've put aside a very small resitive heater classic boiler (50 liters) so I have had exactly ZERO "service interruption", in that case the problem is that something is cheap to back up, something is definitively not... For instance I have one of the first thermodynamic VMC (a double-flux VMC with a heat pump heat exchanger instead of a passive one) and being in a new home I can't stay without a VMC for more then few hours or I have to open the windows no matter the outside temp. Well, I've also choose to have a backup but it's just a passive VMC since spending 4k€ to keep a secondary cold spare it's definitively wasted money. The small resistive water heater was just 150€ in total plumbing materials included, mounted by myself so a reasonable backup. Similarly the main heating (water-water heat pump) have no electrical backup, I've chosen AND I REGRET a small wood stove for modern homes (Jøtul Scan-66) and I keep a bit of wood (used in the spring to cook pizzas outside, so it remain moderately "fresh" since it's renewed any two/three years). I regret because for not much more I've should better chose a wood based boiler and a LARGE insulated reservoir to make hot water in few hours for an entire day and the small p.v. LFP batteries suffice for a pump. Long story short: most technicians do NEVER think about when something goes wrong and most do not even have at their own home the "new" systems they design so they do not really know them beside theory.
- teekert 3y agoInnovation in building and tech is going too fast for these small installation type companies. Zigbee, sensors, switches, motion sensors, per room heating, insulation, decentralized heat recovering ventilation, heat recovering sewage pipes, (noisy?) heat pumps, CO2 sensors, particle sensors, hybrid heating systems, house batteries, solar panels, heat panels, car chargers, vehicle to grid, smart appliances, variable electricity rates, dc subgrids… An enthusiast can make a home so much better, more comfortable and efficient. But non of it is easily obtained the way we obtain our old gas heating systems. And it drives me crazy, it’s so complex, it costs me so much time, but I just see so many “professionals” contradicting each other, I hate that I have to make all these choices.