Are Air-to-Water Heat Pumps Finally Ready for Extreme Cold Climates?

You need to do the homework when considering on a A2whp

The required operating temperature at design condition is one critical number.

Staying below 120 is a good goal. So large surface area emitters like radiant panels work best.

Data is available from manufacturers and independent testing on efficiency drop as outdoor temperatures drop. No guessing required. Same with performance at higher operating temperatures

This info, in graph form was in my installation manual. Realistic numbers not sales hype.

Operating cost comparison is directly related to the various fuel cost at the insty locat. That data is also available going back 30 years or more. The question is fuel costs going forward?

I would also pull the data to see how many days a location is at or below design when considering a backup system.

Some do, some don’t consider the installed cost of a HP. ROI is another hard to pin down number. System longevity is a question Refrigerators have a 15-20 year lifespan, as far as the compressor snd components

Lots if electronics under the hood A piwer conditioner is a goid option.

Qualified installer and service people needs to be considered. It takes multiple skills to troubleshoot a HP

I’m going on 3 years with a Viessmann system running 120 SWT to radiant slabs. Just started running chilled water to the slab for cooling. So far I am pleased with the operation and operation cost

Electric rates vary between 11– 13 cents, and I have enough PV to run the system on sunny days

So for me, all the boxes checked.

Replacing or a new installation on a system needing 140 or more, especially in cold climates. This may end up with some heart break.

An example for the Viessmann

It really depends on the brand.

Viessmann tech support answers the phone. If they are busy they call or txt back within an hour. I've spoken to several different tech support, mostly in Waterloo, Canada a 1/2 dozen times as I programed the unit.

In some cases the local rep for the area is helpful.

Maybe not so for some of the imports from China purchased online.

Longevity is a really important factor in the math here too. There is no reason they shouldn't last 40 years with proper engineering but I doubt that most actually will, maybe the Viessman if they are actually building them in Germany or at least Africa.

Technically, anything above −459.67°F (absolute zero) is said to contain some measure of heat. Therefore, in theory, an air-to-water heat pump should be able to extract at least some measurable heat from the outdoor air at temperatures above −128.6°F, the coldest temperature ever recorded on Earth.

If you have a large enough heat exchanger, you can recover some of that heat, compress it, and transfer the resulting higher-temperature heat into cold water, making the water hotter. You can then use that heated water for something useful.

So, perhaps you could take a shower at Vostok Station in Antarctica! That is where they recorded the -128.6° temperature

Of course, the practical problem is that as the outdoor temperature approaches absolute zero, the amount of available heat becomes vanishingly small, and the efficiency and capacity of a heat pump decline dramatically. Long before reaching −128.6°F, the size of the heat exchanger and the amount of energy required to operate the compressor would make such a system impractical. But from a purely thermodynamic standpoint, there is still heat to be extracted from anything above absolute zero.

I’ve worked of -120*F Freezers. Cascade system. A reverse cascade can be done. Is it cost effective I don’t think so, at least not yet.

I've not had trouble getting Weil, Burnham, Lochinvar, IBC, NTI, ECR on the phone. They all offer A2WHP now.

The key is to get the direct tech support number, or a number place to txt. A contracted "phone answerer" in India may not be of much help.

Odd that the boiler companies are embracing, supporting and training A2WHP. They certainly have more hydronic experience that Mitsubishi, Dakin and Fujutisu. Several offer the intergration control if you want to pair a boiler.

Although many of the products and brands are merely rebadged equipment. I don't know of any boiler manufacturer that manufacturers HP?