Homemade Heat Pump Manifesto (2009)
ecorenovator.org
ecorenovator.org
> I want to take a moment to recognize that the Homemade Heat Pump Manifesto has gone beyond 2 million page views. I would like to thank Daox and any other people who may have worked behind the scene to make it possible.
> My initial goal was to make available the knowledge and possibility that anybody with a few tools and gumption could convert discarded air conditioners, and dehumidifiers into very high efficiency heat ources, or cooling sources. Through the years, we have received reports of success from many people, living in many states, and countries.
> Another goal was to make zero money from this project, to give it away and to encourage others to take it, share it, sell it.
> In the beginning I thought that maybe 200 people would find this interesting. Obviously, I was wrong, gloriously wrong.
The closest solution you could probably find would be for the mods to pin the post to the top, but in my experience most people just ignore pinned posts except in very specific cases.
https://www.reddit.com/r/changelog/comments/25kvjo/reddit_ch...
Even if all of this would be in a Reddit thread I’d argue the usability of their site has declined to a point where using it for longer reading is unpleasant. (Login-Wall, collapsed threads, slow JavaScript frontend)
So yeah discoverable yes, but nobody would use it like that.
Not anymore.
That format just promotes reposting and restating the exact points that were popular 6 months ago. There have been many times I have had something to contribute to a discussion and have been rebuffed by the "This thread has been archived" popup. Truly any thread more than a year could not survive most current social conglomerates, I understand the scaling issues but it does not make it untrue.
Faaaack, I’m still maintaining this 17yo Toyota. I need those brake change pictures!
On web forums, a new comment on a thread automatically bumps that thread up to the top of the thread list, which means that even after a pause, existing threads gain traction like if they were new threads. (Possibly even more than new threads, due to the existing contents.) That way it’s easy to have a focused discussion for weeks/months/years on a particular subtopic.
In any case, I’ve never experienced reviving old threads to be a significant issue, or to happen inappropriately to any significant degree.
I realize that where i am enthusiastic about older things, cars/bikes/tech/languages, you probably like new stuff. I hope you realize that most of the zombie revivalists agree with me. Most of the time we are looking for a new solution to an old problem, which is the definition of progress. Locking threads after 6 months (thanks Reddit) or berating someone who want to revive an old topic, cripples progress.
What we need are search engines to offer an opt-in view or keyword which prioritizes this genre of valuable older evergrowing content. Perhaps Brave Goggles can be adapted to this purpose, using HN reposts and other signals of longevity.
The great thing about old style forums is that you'll check it once in a while and just go looking for the "latest" message, almost like joining IRC after a few days. You can go look at earlier messages but it's not always necessary.
Or am I wrong - can you make some sub-reddits work that way ?
For the rare times I want to navigate to that cesspool I have to manually change the URL to “old” but it’s just a matter of time before they get rid of it.
Not to mention all the other issues that plague the site. Archived posts, dead links, deleted posts, deleted comments, deleted entire subreddits, and more. It’s not a place to effectively find older content much less truly old content. And worst of all the search function is comically useless so much so that there is practically zero self discovering within Reddit itself. You must exit Reddit and search on a search engine with “reddit” at the end of your query.
What a junk site.
> outside temperature is 10,0 degrees Celcius, inside T is 21,1 and incoming fresh breeze (top) at 19,0!!
2016 pipe design with 3" metal duct inside 4" PVC pipe, https://www.loudawson.com/17884/how-to-build-air-cross-flow-...
2012 box design with aluminum foil on wood frames, https://makezine.com/projects/heat-exchanger/
Elegant $100 commercial window HRV, discontinued (why?), https://www.amazon.com/Bionaire-BAP336M-U-EverFresh-Exchange... & https://ia904509.us.archive.org/29/items/manualzilla-id-7067...
You can use something like rock wool (in batts or panels) to get insulation that is still vapor permeable and water resistant.
You can use smart vapor control layers (such as Intello) to counteract this - but be sure you’ve discussed how the wall can dry out if it gets wet.
And the worst of all is if you end up with two vapor barriers - one on the inside and one on the outside - you’ll end up with a “dirty diaper” effect.
https://www.buildingscience.com/documents/digests/bsd-106-un...
so what do you do when it is 100 degrees outside and 70 degrees inside during the summer, and 30 degrees outside and 70 degress inside during the winder? Move the vapour barrier?
However, what I have found in the process is that for well insulated homes GSHP probably doesn’t make sense.
Originally I was considering buying a kit from this site: https://www.123zeroenergy.com/pricing/geo-thermal.html
But like it says on the page, because air source heat pumps have been getting a lot better they no longer sell the kits. There are a couple of individuals on YouTube who have used similar GSHP kits and had good success. The main challenge is that you need to dig 100ft of deep trenches per ton of cooling. Edit: should be 300ft not 100
This sort of take is unwise. It makes zero sense to invest today in domestic systems with the expectation that at some point in the future there will be extreme events a hand full of times throughout the year. The benefit of shaving a fraction of a percent from the baseline outweighs multipercent gains of hypothetical extreme events that happen a few times a year.
When building spend as much as you can on the building envelope (preventing air, vapor, water movement) and insulation.
Those cannot be easily changed at all, but you can relatively easily add another heating or cooling device.
And if you build above code minimums (you should!) be sure to have someone knowledgeable calculate the actual heating/cooling load. If you don’t, the HVAC contractor may assume code minimums and oversize the system.
Or get systems that are entirely variable.
And get every step inspected! Mid build blower door tests are a great thing to do (right after the air seal envelope is up).
Great point.
Investments are made based on expected returns on investment, and we're free to postpone them until they make sense.
Spending money hoping to bank on the occurrence of unexpected outcomes simply can't be justified.
I would have agreed a decade ago, but in the one year our house has been standing, it has endured two 100 year events (a heat wave and a rain/windstorm).
We overpaid about $1000 to go one size up on the (variable) heat pump / AC and $10-20k to oversize + harden the solar / battery.
It has been worth every penny at this point; the solar kept the fridge, freezer and AC happy in > 100F heat during a power outage. That's $500-1000 of food just for the one event, and outages are increasing in frequency. (Air conditioning was mostly unheard of in this area 20 years ago, since it didn't get hot enough to ever run it.)
My big concern is that we're already eating into the engineeeing tolerances for the wind rating on the house itself.
I do agree that you should consider what can be upgraded later, and put money towards things that are hard to change (insulation, wind ratings, etc.)
That's a terribly silly thing to say. Think about it for a second, particularly how insurance premiums compare to the cost of buying/rebuilding a new item.
Maude: Uh, well, no. Neddy doesn't believe in insurance. He considers it a form of gambling.
For older building even replacing wood furnace with air to water system is enough.
It also has the extra benefit of heating up your ground for the winter period.
Of course this makes the system more complicated. More complicated means more chances for failure and higher costs for designing and installing.
While this might not be needed in Sweden, it's more interesting further south. I live in Belgium and we had a long heatwave this summer and they predict more of those in the coming years. So cheap efficient cooling might turn out useful here (even if nobody had AC systems 20 years ago)
My considerations for going with ground source heat pump were:
* the maximum amount of solar that I could install is enough for ground source heat pump, but is a bit short for air source,
* what if the seasonal electricity prices get so extreme, that the grid can't maintain 1:1 ratio for the net billing system anymore?
* what if the global temperature swings become more extreme?
https://weatherspark.com/y/71566/Average-Weather-in-G%C3%B6t...
in contrast sunshine duration and angle in Winter is frickin low.
sure that guy wasn't trying to sell sth?
https://www.heatpumps.ca/articles/best-low-temperature-heat-...
I'd love to believe that modern ones are better, but its hard to pull the trigger on them after years of suffering.
I currently have oil heat, and love it. Nice hot (not luke warm) air. And if the power goes out, I just fire up a generator and I have good heat, because the blower doesn't take much to run. Having been w/o power for stretches as long as a week during winter, that is a massive benefit over electric heat.
The common Asian 'mini split' models also use variable fan speeds to maintain higher coil temps and have output air that is warm enough to avoid the 'luke warm' issue of heat pump coils on 'dumb' air handlers that blow full speed.
That said, for cold environments, a backup is often required to make up for the performance drop at very cold temps without massively oversizing the system. Hopefully, you have your oil furnace coupled to a heat pump or perhaps supplemental minisplit heads. That is the best of all worlds: the HPs can cover 80-90% of the load, only needing the oil for extremes. Oil is likely to hit 5 a gallon this year, like last, so it would suck to rely entirely on it.
Particularly noise and heat locality. Two properties that combined are not very cosy.
Mitsubishi, specifically, makes a heat pump with the marketing vernacular, "H2i" or "hyper heat" which has reasonable efficiency down to -13F/-25C.
My mini-split system worked fine down to about 10F, then it was defrosting for 10 minutes after every 8 minutes of use or so. I just turned on crypto miners on a few computers to supplement. Laptop crypto mining is useful if you want to keep your hands and wrists warm, hats, blankets, sweaters, and some old 100+ watt light bulbs will also help.
All this is to say "you can just get a -30 degree capable system" is out of reach for most people in the world. A large swath of people geographically close to my house still use window or wall HVAC units, rather than ducted systems. I was the only split ductless system my HVAC installer had ever installed - they had to come fix their install 4 times (four!) and eventually i contacted the asurion purchase protection people and got refunded for the cost of the HVAC system.
it works fine now, i told the HVAC installer to cut the threaded connectors off everything and sweat all the copper lines together, and it hasn't had an issue since.
it was always breaking in the late fall and early spring, where it had to heat at night but cool during the day, it would always break around 11AM. The pressure differentials must have been an afterthought in the design, i guess.
the system i have now is also a minisplit, but it has 5 heads, and is 5.5 tons. If i run one of 4 heads by itself, it can do 3 tons to just that head. the fifth head is smaller BTU, i think it's 3/4 ton max. It cost $3,723.68, plus an additional $5000 to get it installed and working, give or take. As i mentioned, i got the $3723 refunded due to manufacturer's defect.
> "The kicker is, that the smallest I have been able to find is four ton (48,000 BTU/hr). So this means that in order to proceed with the project, I'll have to build my own heat pump. In HVAC, bigger is not better... just slightly smaller than big enough is best, economically speaking."
Is he saying here that a heat pump that's too large for a space is less efficient at heating, or is he just saying that a bigger one costs more to buy?
If it's the former, can anyone here tell me why that is? It's hard to Google since it gets mixed up with other info like "heat pumps are less efficient at very low temperatures" etc.
I would have thought they'd end up the same. The only reason I can think of is that a bigger one will maybe turn on and off more often to maintain temperature than a small one that's on all the time struggling to keep up.
Edit: Thanks all for the excellent responses.
The main factor for good efficiency is low output temperature- underfloor heating works at ~35 deg C, radiators work at ~55 degC (because of smaller surface area).
I sized my heat pump based on historical data of heating oil /diesel consumption- since I had the data of past two winters, I could reliably determine the maximum continuous heat requirements for my house.
Essentially, you want your HVAC system to run for long enough it’s a gradual transition in temperatures inside and the equipment can run for awhile each time it needs to run to avoid the start/stop problems and let it ‘settle in’.
As I understand it, it comes down to a couple of things.
Heat pumps are much more efficient when providing lower temperature flows, their efficiency drops off significantly where the delta between the heat source (air or ground) and their flow temperate is higher.
When an oversized heat pump cycles it is going to quickly reach a higher temperate and shut off where as a correctly sized unit will cycle for longer. So I guess simply it comes down to having the heat pump operate in the most efficient range for that property for longer vs. short spikes at temperature where it is less efficient.
Most heat pumps have a variable speed motors so they can modulate their output to match a desired flow temperature but this only operates within a range relative to the size of the unit. So if the unit isn’t correctly sized for the required heat output to be in its range then it has no choice but to cycle inefficiently.
A couple of sources I found helpful:
https://assets.publishing.service.gov.uk/government/uploads/...
Most of the consumer advice is very low level - this Heat Geeks site seems better that most, but it still lacks enough detail for me to get into the numbers: https://www.heatgeek.com/3-steps-to-maximise-your-heat-pump-...
I'm quite curious because I have an old-ish heat pump that's a little small for the space and I've been thinking of getting a larger one. But if it'll be less efficient then maybe I won't. The one I have does perfectly fine except on a few of the coldest winter mornings.
800 watt for the refrigerant pump, and about 100 watt combined for the two fans.
This means even when I'd like it a little warmer on the coldest days, making the heat pump use more power isn't an option.
A larger unit would have a bigger refrigerant pump and larger fans. This would result in us inadvertently leaving the unit on a higher heat setting more often.
Also, a larger unit will be turning a larger pump and larger fans even when smaller would achieve the same outcomes. Mechanic losses.
These two factors, human habit & mechanical losses, are, as I understand it, why you're generally better off having more small systems than one big system.
We have three split systems, in addition to the 7kW unit at one end of the house, there are two 2.4kW units, one I'm each of the bedrooms we use. When one or more units aren't required they can be turned off. Another advantage of this setup is that it's extremely unlikely all three systems will breakdown simultaneously.
Another issue with the larger units is they tend to be ducted, where the ducting is in a poorly insulated roof space, so there's additional heat losses there, and additional losses due to energy required to push air through the ducts.
Agree that multiple smaller split systems is the way to go though.
Your second argument is silly: a larger pump will surely take more energy to run but will run for less time. It’ll also wear out slower as it doesn’t have to work as hard unless you have drafts and it has to cycle on and off all the time. Generally having more capacity is always a good thing for mechanical things.
> if you have a large compressor, you pay more for it with every revolution the trick is to figure the maximum BTUs or watts you will need, and design a little bit smaller. Plan to use a supplimental energy source to fill in during extreme conditions.
Worth noting the AC_Hacker paid $25 for the AC he used for this.
> Most of the consumer advice is very low level - this Heat Geeks site seems better that most, but it still lacks enough detail for me to get into the numbers
You'll probably want an undergraduate physical chemistry textbook for this.
When it is slightly undersized, it'll run continously and also prolonging compressor life...
Compare this to being able to drive continously at the same speed vs. having to stop/start every 500m or so...
I really tried to verify the horizontal coil length and installation depth recommended by installers from the first principles, but I had to give up, as there were just too many unknown inputs: the type of soil (thus, specific heat and heat conduction), water content (which varies over the year), received solar energy (shady/sunny).
[1] https://www.greenbuildingadvisor.com/question/what-is-minisp...
When I looked at the insides of the pump, the simplicity of construction was surprising- I could readily understand whats going on, as it consisted of off-the shelf parts made by other companies- compressor, circulation pumps, VFD and heat exchangers.
A bit off topic, but I really think the existing forum sites aren't really that incompatible with "younger" people, and might have a renaissance later on (looking at how they are using Discord in a similar manner!) It's just that these old forum sites have lots of UI clunkiness that deter people from browsing or joining the site (older people who kind up grew up with phpBB might be accustomed to these sorts of jank, but you shouldn't expect someone who weren't in that era to be accustomed to it.)
Then you also avoid the annoying 'you must create an account to view attachments'.
Sadly most of the admins for these type of fora are just learning as they go.
As someone who’s never lived in a house with AC, is that loud(er) or quiet(er) (than an AC unit)
I get that if your heart is set on having a heat pump you need a heat pump, and that's the end of all financial consideration.
But how does, say, $10K of heat pump compare to $10K of insulation and better windows/doors/roof, or $10K of solar panels and cheap ultra-low-tech repairable all-electric HVAC, or $10K of some other form of physical investment I'm not aware of?
If you have a perfectly serviceable means of heating that you are happy with, then it's a straightforward cost analysis (cost of consumables for the current heating method vs cost of electricity for the heat pump).
I can only give an example that applies to my situation: previously I burned ~2300l of diesel which cost around 2300EUR for the previous heating season. So the yearly energy consumption is about 24MWh (combustion heat of fuel multiplied by efficiency of the furnace of ~94%). If I were to install air source heat pump, it would require about 8-9.6MWh (COP =2.5-3) of electricity per year (4000-4800EUR at the current fixed price offering from my electricity supplier of ~500EUR/MWh).
If I were to install a ground source heat pump (COP of 4.5-5.5), expected electricity consumption is between 4.3-5.3 MWh or ~2200-2600EUR/yr.
If I were to power the ground source heat pump using the electricity generated by my solar panels (Latvia currently has 1:1 net billing system, but there is a grid cost of ~50EUR/MWh) the expected yearly heating cost is ~210-260EUR.
At the previous electricity cost of ~100EUR/MWh, air source heat pumps for not-so-well insulated houses might be attractive option- but not at the current prices in Europe.
When I did the calculations this spring, the break even time for heat pump + solar installation was ~8 years (based on fuel and electricity costs at that time).
Right now it's around 4 years (and I might even get ~40% of the investment from a government clean energy incentive programme). However, I have to operate under assumption that a crazy dictator of a neighboring country doesn't decide to invade and wipe my house off the Earth...
Solar panels probably come in second because they create waste energy that unlocks free EV charging, etc, etc (but you will pay more than $10K for the system), so, thanks to sunk costs, other stuff becomes "free".
Heat pumps are probably the cheapest big bang for the buck upgrade for existing construction (especially if you have to replace your HVAC anyway). Minisplits are often a big win for retrofits of buildings without central air.
All of these things are dominated by labor costs, and we are in the middle of a labor shortage. You are unlikely to find realistic financials unless you get bids and compare with your personal energy rates.
We didn't do any of that.
We just assumed energy prices would continue to explode over time (we were right), and jumped off the inflation carousel by putting in solar and all electric appliances.
Also, we can't get natural gas service, and propane costs 4x per BTU more than natural gas around here. Most electrical appliance upgrades are subsided by the government to make them competitive with natural gas.
That made it a no brainer.
Since then, a bunch of indoor air pollution research showed that natural gas causes asthma, etc, etc. Also, the war in Ukraine started.
So, what are your health, future financial predictability, and engineering economics braincells worth? For us, the answer was "less than the installation cost of the system".
Also, after all they put us through, seeing a -$120 bill from PG&E each month makes me irrationally unhappy. ;-)
I want a picture. Walking through the front door must feel like going through a tunnel.
This is similar to an “earth house” and is very comfortable where the average (or basement) temperature is comfortable. The walls make an insane amount of thermal mass and the temperature inside changes very slowly.
Europe spans 40 degrees of latitude - not listing yours is dishonest.
See https://www.danby.com/blog/danbys-commitment-to-remain-100-h...
http://hvacrfundamentals.blogspot.com/2019/06/appliances-wit...
Looks like r600a, iso-butane is already in use.
Wish we found a solid way yo harvest heat from waste water. So much energy is wasted on showers - similar to EV driving at highway speeds.
It's only expensive due to the amount of copper. The actual install has no moving parts and is completely passive.
https://www.nrcan.gc.ca/energy/products/categories/water-hea...
I used a very modern heat pump dryer in Switzerland all summer and "... longer to dry clothes ..." is an understatement.
A normal, mixed load of clothing took a full 2.5 hours to fully dry.
It reminds me of CF lightbulbs: a failure to solve the real, big problems (efficient and clean generation of electricity) leads to widely distributed pain for end-users (dryers taking hours or terrible, dim, purple lighting).
Far more interesting than hyper optimized electrical loads would be abundant clean energy sources. I would rather have solar panels and free electricity than have utility power and weird, complicated clothes dryers.
... and yes, my analogy is imperfect because the lighting issue was elegantly solved with LEDs. That's unlikely to be the case with clothes dryers, however ...
I would definitely like to read a detailed description of his pump unit.
https://www.agas.com/uk/products-and-services/refrigerants/r...
Ticklish though I'm sure to do it properly and safely.
You may be thinking of acetylene. But that isn't really that dangerous in modern usage either.
It doesn't have to explode to burn you though. Where is the purge gas escaping when used this way?
I have no idea what you mean by "purge gas".
1) their owners insist they are the greatest thing ever and
2) nobody in the midwest seems to sell them (at any price)
I don't quite know how to reconcile those two things.
If you live in the north where temperatures go below -15 Celsius, air-to-air units aren't as great because they lose efficiency as it gets colder outside. My heat pump has a COP of 3, meaning it can generate as much heat as a resistive heater using 1/3 the electricity, but it shuts off at -15 Celsius because below that point it is less efficient than resistive heat. If your heat pump has a COP of 4, you might get to -25 Celsius before it is less efficient than a resistive heater.
Better, but more costly, heat pumps use in-ground water, either from a pair of wells, or from a deep pond that won't freeze to the bottom, or from many meters of water pipe buried deep enough beneath your lawn to not freeze in the winter. Because of the depth, they always have access to the earth's heat so they don't lose efficiency in the winter.
The Technology Connections YT channel has a couple of good videos about how them:
Why? Slightly less air replacement required to fend off mold, slightly more heat created, because the condensation is the inverse of evaporative cooling. Haven't done the math but I think it's safe to assume that the benefits would be tiny, but if, for some reason, you were limited to resistive heating, doing it this way would be slight ly less bad.
Lots of reading, being willing to try something, welcoming failure as also a learning moment.
The project is cool, but if the project caused a water leak or fire you are probably screwed and wont get anything from the house insurance.
all the common ratings that i've found online refer to COP at a non-zero delta-t over a ranges of conditions. to illustrate my question, if you needed to pump heat from 70°F indoor air to 70°F outdoor air with a 1-ton unit, what would be the best COP you could achieve in 2022 ?
I suspect it could work but it’d be marginal enough as not to be worth it compared to straight air heat pump or an actual field (similarity could a heat field and a septic field be installed at the same time ,,,)
However, a well may be "just poking" into that territory so you get the right temperature, but not enough surface area to do much heating/cooling.
They're considered better than air-to-air heat pumps which become less efficient as the outside temperature goes down. Ground source units remain efficient in cold weather as the water in the well is below the frost line (only the top few feet of the soil freezes). They cost four or five times more than a typical air-to-air unit though so aren't as common.
I think this manifesto is a piece of genius - I think I shall be studying :-)
How is every house builder going to afford a million quid borehole?
From what I've read through, replacing my boiler with a gshp would cost in the tens of thousands, not a million pounds.
Then all we need to do is start turning the natural gas into hydrogen - releasing just as much carbon dioxide as burning it does - and we've got a clean green hydrogen economy!
Is this something people do?
Up here you end up with the outdoor part freezing into a block of ice.
The problem is that the outdoor part has to be, well, outdoors, and that's where all the water is.
If the UK Government appears to be doing something "good for the environment" you can rest assured it's only because they've found a way to use it to siphon money out of the public purse.
Makes sense for flats (or dense area of many leasehold houses, if that happens) where there's a management company holding your throat anyway, but otherwise I can't see how it works unless perhaps it was provided by the council (similar disadvantages, just more trust/better outcomes from complaints).
It's normal for temperatures in Scotland to dip below -5C over winter - do ASHPs not work at those temps?
Many even now are (blower on/off) and (flame on/off). Only the high end ones have variable blowers and flame heights.
I know this because before ours was replaced I had to jumper past a bunch of the board to keep it running.
There's a few other safety checks the board will do.. check pressure switche to ensure there is draft before attempting to open the gas valve and light off. There's also thermal limit switches to make sure things don't get to hot if your main blower goes out.
I lived in the mountains of Southern California. As part of an FHA loan in buying my childhood house from my dad, we had to "upgrade" from a swamp/evaporative cooler and wood burning stoves and went with a heat pump. The unit and ducting just couldn't keep up. It sighed out slightly warmer/cooler air and, when it kicked on, it pushed outside-temp air into the house that, in winter, would take the unit over an hour to bring the house back to its starting temp, let alone warm it. It really sucks to be cold and to have to get colder before a chance at warming up. It was similarly lame at cooling, though it would keep the house from sweltering if started before sunrise. Temp range outside: 20-40s in winter, up to 90s with a couple of days in the 100s in summer.
We went back to the wood burning stove and swamp cooler.
We bought such a portable AC unit as an emergency measure during an extended heatwave and wildfire smoke event in the past. We bought the better kind of unit that has intake and exhaust hoses for the "outside" loop. Astonishingly, there are even worse products on the market that lack an intake hose. So they, by design, draw conditioned air through the output loop and then through the exhaust hose! You can imagine how inefficient that is, to be pumping air out of the conditioned space and create a negative pressure across whatever other leaky paths can refill the room.
Our portable unit with intake and exhaust hoses still does not work very well and leaks a lot of outside air into the conditioned space, obviously reducing indoor air quality when used on those smoky days. We had to hack together a big intake filtration box to keep the smoke out by drawing the intake air through a set of MERV 12+ furnace filters. We also added fiberglass insulated sleeves to the air hoses, which improved thermal and noise comfort.