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
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.
This comment section is a trip. Any time anyone is like "I have reservations about my own heat pump" and people are just responding with downvotes and "no"
I mean, it’s fine to have issues with your own unit. The only issue I personally take is when people (not this individual to be clear) use those issues as a counter argument. It’s like saying “my air conditioner has a freon leak and freezes up every year, so air conditioners are terrible in general.”
I had no idea sharing my experience would be interpreted as a clarion call to fuck all heat pumps straight to hell forever.
I explicitly said no you, ya silly kangaroo.
and I upvoted you twice, friend. :)
I think it's an issue that people are passionate about and the "discussion" just turns into some kind of political shouting match.
Like, it's actually been settled for quite some time: MOVING heat is more efficient than generating it or absorbing it through phase transitions. This study is just one more on a long parade saying the same thing.
What features and installation considerations exist for different climates? Do some manufacturers specialize in systems that excel in different circumstances?
I'd be surprised if they didn't. I'd be really interested in hearing who the premiere manufacturers are who design systems intended for use in Northern Canada. I'd be interested in who makes best systems for use in Phoenix. I can't imagine the same system is ideal for both places.
That's an interesting conversation to have. "Mine doesn't work good" "yes it does, fuck you" is tedious.
Right but efficiency doesn't mean it's better. Electric heat has always been 100% efficient, but that has not made it the most cost effective nor the best solution over far less efficient means of generating heat either. Efficiency isn't the only factor. The debates and critisms here are valid from what I've seen.
Personally, I'm not sold on them... maybe if I lived someplace warmer but living in Wisconsin, they are not for me. I've also seen that they require a lot more maintenence and are much less resilient compared to furnaces and central air units. I've watched plenty of installation and repair videos on them. Even the HVAC guys have issues with them in these terms.
The thing that blows peoples mind is that heat pumps are MORE than 100% efficient.
WWHHAATT?? WHAT ABOUT THERMODYNAMICS??
Heat pumps don't GENERATE heat. They move it.
In the same way that a locomotive can expend a few hundred gallons of diesel to MOVE a few hundred thousand, so can a heat pump MOVE more joules of thermal energy than it expends in the moving process.
Heat pumps are more complex then a natural gas unit, absolutely. Depending on what you're paying for energy, it's entirely possible it's not cost effective right now.
But,as the tech improves and energy costs increase, the break even point will eventually meet you, even in Wisconsin. If it's not for you right now, that doesn't make you a bad person.
But keep your eyes on it and don't write it off. I don't know how old you are, but it's still likely to end up the most effective choice for you at some point in your lifetime. Certainly in your children's.
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.
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.
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.
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!
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.
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.