Your whole argument is. Heat pumps need a secondary heat source because at the temperatures around 0C they accumulate ice on the heat exchanger outside. To melt the ice they reverse the energy flow so they cool the house and heat that heat exchanger. You asserted that it's just FUD and they can "redirect some heat" instead. This implies they don't cool inside and instead redirect heat from elsewhere (second outside heat exchanger perhaps?).
But it appears there is no second heat exchanger outside and the modern heat pumps work just like heat pumps from couple years ago.
As for keeping the functionality - it's a philosophical question. For me personally, if I turned on the heater because it's cold inside and it started blasting cold air, I'd call the repair people immediately. While it still works in the sense that it makes noise and consumes energy, it stopped performing its function of heating so I'd consider it lost the functionality I am interested in the most.
"Redirect some heat" from where? In the installs I've seen they did it from inside the house i.e. literally cooled the house down. The alternative heat is needed to keep the inside temperature up and work against the pump cooling your house down when it's already cold. Do you have some other alternative source of heat on the modern heat pumps?
>Modern heat pumps redirect some heat to prevent the coils from freezing. What you wrote is common FUD pushed by the oil & gas companies.
It's not FUD, and you COMPLETELY ignored & omitted the rest of my sentence from your quote. I'm well versed on how heat pumps work. I was not saying heat pumps don't work below freezing. Rather than simply repeat myself, let me rephrase:
1. Heat pump efficiency gets worse the closer you are to the minimum (outside) temperature they're rated down to.
2. Even with the best (and most expensive) technology, that means efficiency of these units approaches that of a $15 space heater.
3. When it gets TOO cold, they can stop working entirely if they don't have a resistive backup heat system (which, again, is effectively a $15 space heater you paid a lot more for).
Both Canada & the northern US experience these temperatures occasionally (-10f to -30f and worse on some occasions).
Hence the need for backup heat - e.g., a pellet or wood-burning stove, backup furnace running propane or natural gas, or even just something cheap and simple like a $150 portable diesel heater. You don't want to be left without heat in a multi-day power outage after a half inch of ice and high winds.
For backup heat, it's more efficient to burn whatever fuel for heat than run a generator outside to power space heaters or a heat pump at those brutally low temps that often follow those hard ice storms.
> Despite the name, heat pumps do not generate heat – they move heat from one place to another.
Literally nothing about "pump" implies it generates heat. That being said...
> In colder climates, an electric heat strip can be added to the indoor fan coil for additional capabilities.
That would just be... electric heating, but with more steps? I mean, at that point you just have a heat pump _and_ electric heating; a hybrid system. It's better, sure, but it's not really just a heat pump anymore.
> You can still use a heat pump that takes the heat from the exhaust air to warm the fresh air
Unless I'm misunderstanding part of this proposed setup, I'm pretty sure this doesn't work. The higher efficiency of heat pumps comes from the fact that the outdoors is an effectively infinite (for the purposes of a house) source of temperature differential. You can only move as much heat as exists, so you can't use a heat pump to multiply a finite heat source.
> You're basically just running the heat pump backwards to provide heat instead of air conditioning
It is absolutely not that simple. Even a passing knowledge of heat pump technology as actually implemented would dispel that simplistic idea.
For example, one of the biggest issues to contend with is condensation. Making your outside fan unit cold instead of hot will quickly destroy it due to moisture accumulating in ways that were not expected.
> The best mental model for a heat pump is that they can maintain a certain temperature differential, say 80F. If it gets to be 0F outside and you want it to be 70? You don’t need to switch to a fully separate heating system, you just need to warm up either the incoming or outgoing air an additional 10 degrees via a small resistance heater.
Are your 70 and 80 switched? What you describe doesn't sound like it needs any addition.
> Why do you say heat pumps only work in well insulated houses with large radiators?
Because heat pumps operate at a lower flow temperature than boilers. Smaller radiators designed to operate at hotter temperatures won't bring your house up to the target heat temperature operating at lower temperatures. They often need replacing. [1]
Trials of heat pumps in existing UK housing have found it difficult giving away heat pumps for free, because of all the extra work required for them to operate properly in the house. [2]
> Heat pumps are ~3x as efficient as the best gas furnaces so why would you need a better insulated house?
Heat pumps in comparison to conventional boilers are meant to be on all the time at a lower temperature, as they take a long time to bring a house up to target temperature.
They depend on good insulation, otherwise the heat never accumulates, similar to if you leave a freezer door ajar, it will never freeze.
> So why would you waste all that energy converting from renewable electricity to hydrogen then burning hydrogen (which is not super efficient anyway)?
At times, renewable energy drives electricity prices negative. We haven't got many ways to store this when it happens, converting water to hydrogen would be a good candidate, which can be delivered using existing gas infrastructure.
> Plus, heat pumps already work at scale
Not in existing UK housing, which would require major changes (insulation, underfloor heating, larger radiators), before they work.
I'm having a hard time finding good information on this, or at least I was a few months ago when I was looking into whether I'm being stupid for thinking essentially what I said in the last paragraph. Do you have a link where I could read more about why it makes sense for heat pumps? I don't understand why the same logic shouldn't apply there.
> "Heat pumps use refrigerant to condition the air in your home by adding or removing heat through thermal exchange."
This is what air conditioners do, too.
> "Air conditioning is a cooling system that circulates cool air into an enclosed space, creating a comfortable atmosphere and improving indoor air quality."
This is what heat pumps do, too.
These are two sentences that describe the same process, just in different words.
The last quote is potentially relevant: a heat pump is an air conditioner that can run in reverse to provide heat in the winter, so you're running it in both situations, and thus for more time.
I never claimed heat pumps don't work in cold weather. The point is about non-electric redundancy, not heat pumps having resistance coils. I'm well aware of the functionality of modern heat pumps.
Even in a house with foam insulation - the highest "normally available" insulation - freezing to death is just a matter of time without heat. When considering city-wide infrastructure it's something that needs to be considered. I'm not saying it's necessarily going to happen, but you'd be dumb not to think about redundancy measures, hence my top-level comment.
This type of redundancy is why many commercial buildings have gas generators, for example.
> if the heat pump is designed to operate in very cold weather the minimum efficiency is 100% (backup resistance heating), so you will always at least break even versus pure resistance heating.
But the heat pump has a "outside" part, where there is a fan and other electrify using stuff. Can you not risk that more heat is generated outside than is moved inside?
"Miscommunication" was probably poor wording on my part. What I meant was that their experiences, like mine, probably involved years or even decades of poor experiences with heat pumps in cold weather, so they were assuming that heat pumps haven't significantly improved in that regard.
Interesting, I’ve never heard of that interpretation. Heat pumps have always been a technology to me. The same tech that is in everyone’s refrigerator.
> so we can see where in the world heat pumps are most effective.
They're not efficient when the temperature drops below a certain point. This is predictable and based on system design criteria. It doesn't mean it's not effective, it's just that it wouldn't be a reliable source of heating year round. It may still make a worthwhile addition to another system, or combined with several other upgrades, may become an acceptable single solution.
> The downside is that [heat pumps] don't work well in cold temperatures.
There are now low temperature or "hyper heat" heat pumps which can function effectively to temperatures well below freezing, some as low as 5° F (-15° C).
Your point is not "wrong", but simply "somewhat less true than it used to be".
Your whole argument is. Heat pumps need a secondary heat source because at the temperatures around 0C they accumulate ice on the heat exchanger outside. To melt the ice they reverse the energy flow so they cool the house and heat that heat exchanger. You asserted that it's just FUD and they can "redirect some heat" instead. This implies they don't cool inside and instead redirect heat from elsewhere (second outside heat exchanger perhaps?).
But it appears there is no second heat exchanger outside and the modern heat pumps work just like heat pumps from couple years ago.
As for keeping the functionality - it's a philosophical question. For me personally, if I turned on the heater because it's cold inside and it started blasting cold air, I'd call the repair people immediately. While it still works in the sense that it makes noise and consumes energy, it stopped performing its function of heating so I'd consider it lost the functionality I am interested in the most.
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