this post was submitted on 12 Sep 2023
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They're only two to three times more efficient if they aren't frozen solid. Don't know how it works in Canada, but my mini-split heat pump can't handle a week of 10F let alone -20 C - sure it will put out some heat, but it absolutely needs to be supplemented with my wood stove. And I live in the South. Maybe there's some new high tech heat pumps that cost a fortune and don't freeze over in the insane temps of the great white north? EDIT: hey, folks, how about actually responding instead of downvoting me? If I don't have a clue, please enlighten me. Fuckers.
Your mini-split isn't designed to function as a heat pump at low temperature.
In places like Sweden, they also use heatpumps that are designed for those conditions.
In other news, don't drive in a Swedish winter with summer tires.
Excellent. Now I know that there are different classes of heat pump. Mine is not for prolonged crazy-low temps, others are. Thank you.
Indeed, but yours is probably cheaper and more effective at cooling when it's hot and humid out.
For people up north, they will buy a "cold climate air source heat pump". In temperate regions, an "air source heat pump" will suffice, while down south you will buy an "A/C with a heating mode" (also called reversible A/C).
And it's not just about whether the coils can defrost. The whole machinery and refrigerant are different to optimize under those conditions. A cold climate heat pump has a setup that is more similar to a freezer than it is to an A/C.
Sorry about the downvotes. People need to re-learn internet etiquette.
This is the most informative answer yet. Thanks.
Thanks for spreading correct knowledge, as someone who works for a manufacturer of heat pumps it's refreshing
I have never seen so many winter tires, and studded winter tires, as I did on my trip to Sweden last winter.
I think they are mandatory there.
My air heat pump has been ticking away happy for 15 years with no issues. It's worked fine warming up the house when it's -20°C in the winter and cooled nicely in the up to +30°C in the summer.
I do supplement it using electric heating and a fireplace though.
Thank you for responding and sharing your counter-experience. Greatly appreciated. What keeps your unit from icing over? Are they designed differently in northern climates?
Here's a good video showing how the heat pump will reverse and basically dethaw the coils when it freezes over: https://youtu.be/7J52mDjZzto?t=1317
They're spreading all over the Alps too. Easily a 50° temperature difference between summer and winter, and they tick over nicely for years with no problems
I think in Europe it's a fairly common method now so reliability has been sorted out.
Generally the US is a decade or so behind everyone else though so it might take a while
Yes, there are cold weather heat pumps that can thaw the coils to keep operating. There is a point where they just can't continue to operate.
When I design a heat pump system in cold climates, I always include a secondary hear source that kicks in if the heat pump gets overwhelmed. Might be a gas section in a furnace. Might be an electric heater in a fan coil. Might be electric baseboards or wall heaters.
You used two temp scales in the same sentence
Theres different technology but there are some that can function to -32° F and they often have a feature that allows them to detect when theyre frozen up and defrost and then automatically switch back to heating
Mine has a defrost cycle but it doesn't work very well. But then again, it's use case is primarily AC - it only gets frigid temps in my area every couple years. EDIT: yes, downvote me for stating my own personal experience, asshats.
Honestly it sounds like your unit may need to be serviced.
A lot of people also don't understand that a heat pump is still heating your home, even though the air it blows might be a bit lower than your body temperature, so it feels "cool." When that happens people assume it has stopped working and switch to aux heat. This is one of the major reasons people insist that heat pumps don't work in the cold, even though they still have plenty of capacity margin to heat the dwelling.
My old system was actually set up so that it would pulse the electric aux heater every few minutes or so to help prevent this "drafty" feeling, and to extend the time between defrost cycles.
Many parts of Canada will regularly see colder than -40F, so I can sympathize easily with a view that solely relying on them might not be safe in that environment.
Tbf, most Canadians don't live in those areas. Places like Toronto/Montreal/Vancouver rarely get that cold.
Edmonton Saskatoon Regina Winnipeg
As a Canadian who doesn't live in the GTA it drives me nuts when people dismiss the rest of Canada as some kind of statistical outlier undeserving of acknowledgement.
Which would account for 5-10% of the Canadian population. Just the three metros I mentioned would account for 35% of Canadians. The record low for the coldest of those cities (Montreal) is -36F, but the average low in January is 7F.
70% of Canadians live south of the 49th parallel (the northernmost point of the Continental US) and 90% of Canadians live within 100 miles of the US border.
It's fine. We use geothermal heat pumps with the lines buried below the frost line. (6-8 feet below the surface.) I know quite a few houses and even a few factories (30,000 square feet+) that use them in temps that drop well below -30c to -40c without any issues.
The initial setup cost is a fair bit more because of having to bury the lines, but after that they're fine.
Oh I have no idea, I just got to this thread and see you're at -6.
It's weird because I thought it was an informative post. Made me want to look more into it and if it was just a subsection of heat pumps that was affected.
I think because I left open the possibility that there's any utility at all to fossil fuel usage, they're treating me like a whacko that's hoarding incandescent light bulbs because I believe LED light bulbs are distributed computing nodes for mind control space lasers or something. I'm not - I was reacting to the article based on my experience with a mini-split heat pump that can't handle a week of 15F weather without freezing into an iceberg, even with a defrost cycle.
Mind me asking what yours cost?
Just got a Toshiba unit installed in Norway and it was $3500.
Built in de froster.
Price might be what makes yours strugle in colder temps.
Mine has Toshiba guts. I don't know what I paid for it - now it appears to be selling for $1100. Mine defrosts but its defrost cycle just turns on AC for a bit instead of heat. Edit: Mitsubishi guts.
I reckon that’s your main issue.
You’d need a model designed for a colder climate.
Maybe for your next one!
Hell that's cheap.
Cheapest quote I ever had was £15k, not including all the improvements to insulation required before the house is compatible..
Mine is air to air.
You were probably quoted ground to air, where they must drill for ground heat?
Yes, most installations do require a backup heat source in the event outside temperature is too low for optimal heat pump usage. On my ecobee thermostat, you can set what this temperature threshold is (i.e. 20F) and then if the outside temperature falls below this value, the heat pump is stopped and the natural gas in my case kicks in. Granted, this doesn't happen often where I live, but for those few weeks in the winter, it is not something I even have to think about. And the rest of the time, I am saving money using the heat pump and not natural gas.
I doubt there can ever be high tech heat pumps which can operate at -25 C or less, because there's so little heat energy outside and the heat pump would probably spend a majority of the time running in reverse to dethaw the unit to prevent it freezing over.
It could probably be done, but then it wouldn't operate at higher temperatures. Realistically you'd probably need two heat pumps, a low temperature pump and a high temperature pump and switch between them as the temperature rises or falls. It's double the cost and double the points of failure, and for a situation that rarely happens probably not worth it.
I'd have to imagine at some point, more heat is leaving the house than entering, and given enough time, inside and outside will eventually reach a cold equilibrium.
Would depend on how well insulated it is, but yeah since homes aren't exactly built to be air tight there's realistically an upper limit to the temperature delta you're going to be able to achieve. Ultimately the question isn't how hot/cold is the inside/outside of the house, but how big a difference are you looking at between those two.
Man they pitchfork mob came out in full force for this one. I also live in the south and during the freeze of 2021 it was a struggle for it to deal with those low temps.
That's precisely the freeze that led me to experience the inability of my Senville mini-split heat pump to keep up. So glad I had a wood stove. Even then, my shower drain trap froze solid. I was living in an "insulated" yurt at the time - good floor insulation, and somewhat okay wall/ceiling insualtion.
My attic insulation needs work. I swear I’m gonna get that sorted this year now that the heat has (hopefully) calmed down.
We probably live in the same neighborhood or something. NC here.
Nope. hollars from tx
Oh Jesus. I’m sorry on so many levels. Unless you’re gung ho Texan. Then I don’t know what to say except enjoy watering your foundation.
There absolutely have been new heat pumps hitting the market in the past year or two that are blowing away the previous generation.
Your mini split probably doesn't have a defrost function. This would all be specified in the users manual.
Oh it does, it's just that it the defrost cycle in 15F gets off just enough ice for it to barely work, and this was when it was brand-new and verified to be working properly. I now understand that it is just not designed for ultra-cold weather, and that some are better suited for such demands.
That does kind of imply it could need a recharge. These cheaper units don't actually have active monitoring for ice buildup - they just do it on a schedule based on temperature (and sometimes humidity). If you are getting ice buildup, it's either outside the rated performance envelope, or it is not functioning as intended.
I think this really highlights the crux of the issue, which is just that the "tribal knowledge" of how to operate the equipment isn't there and it's something that education would probably help.
Like, many people's fathers have probably shown them how to relight the pilot lights on their furnaces and hot water heaters. And if not, the "handy person" on your block would know.
Understanding how to own and operate heat pumps effectively might not be as second nature.
Understanding how to validate the extreme weather functionality of your heating system is super important. Knowing the difference between "normal" and "something is fucked up"... especially before an extreme weather event is pretty important. I'm pretty handy, but absolutely nobody in my area runs heat pumps residentially...
... but that's probably just because of a lack of uptake rather than a real economic reason. Solar is exploding in my area as a result of increasing power costs and a great environment for it.
As it's adopted and as people learn how to use, maintain and troubleshoot them I expect problems like that will become more sparse.