Heat pump sales rise across Europe

While this may be true (have no knowledge | how does it work w/o salts?), the OEM will immediately void your warranty if you use any sort of homeowner water softener, per both Rheem and AOS installation manuals.

I have both; mine are warranted "platinum|10yrs" — why chance it?

>Wait do you install these indoors?

Absolutely. Not just because of the heat, but because large parts of Tennessee are subtropical rainforest (~60+" annual rainfall) so dehumidification is absolutely essential. Why not get free dehumidification from heating water?

Installing an air-exchanging heatpump OUTSIDE?!? is absolutely a massive waste of energy in such a climate (and many more).

>isn't noise an issue?

All four of mine are installed in 20sqft utility closets, using insulated ducting to top-wall registers (also, insulated). For my first install, only, I used a solid metal 90° to pierce the wall/inlet (this one is loudest, basically as if the wall weren't there).

Granted, there is definitely a "louder" side (the inlet-sides), but not by much. None of my utility closets are insulated (from surrounding draw rooms), and the entire unit isn't loud enough to justify more than just a layer of sheetrock on both side of the wall/partition.

If this was installed in a garage, it would definitely be known-to-be-on, but not aggressively-so (if you have a workbench outside, e.g.). I don't know the decibel rating, but it's about the same loudness as a stand-alone dehumidifier (same wattage/concept, actually), without walls.

Should you desire the quietest install, insulate the wall (between studs) and use dual 6" insulated ducting, with switchbacks, for both inlet and outlet (that's a lot of hardware). In such an unnecessary installation, it would be whisper-quiet.

2.3 million a year for something with a 20-30 year lifetime is a lot. It's not quite enough for "in 20 year everyone will have one", but you only need another 5 or 10 years of similar 15% growth to get there.

> I think technically it's 28kW -rated (there's a consumer-installed limit, w/o boilermaker license), but the circuits support more w/o 80% derating applied

A tankless water heater is not considered a continuous load so there’s no need to apply the 80% rule.

A 60A 2P breaker will have a trip curve that results in a thermal trip for just under 100% of rated current in around 2-3 hours. The fast acting part of the trip curve is magnetic, longer duration trips are thermal.

Here’s a link to a Square D breaker guide: https://ressupply.com/documents/square_d/QO_and_QOB_Circuit_...

The trip curve on page 25 of the pdf applies to Square D QO plug-in (residential breakers are usually plug-in, commercial are bolted on) 2-pole breakers rated 120/240V from 45A-60A. Find the 1 (times rated current) at the bottom and follow it up the chart until it intersects with the black area of the trip curve, that is approximately when the breaker will trip at 100% of its rated ampacity. Look at the left hand side to see the time in seconds that it will trip in.

It’s hard to see exactly where it intersects, but it’s somewhere between 7000-10000 seconds, or 2-3 hours.

So, you need to apply the 80% rule to continuous loads because breaker trip curves are adjusted so the thermal overload trips in 3 or fewer hours at 100% of rated ampacity. If you look at .8 times rated load, the line never intersects the trip curve.

Here’s a manual for an A.O. Smith tankless water heater:

> https://assets.hotwater.com/damroot/Original/1000/100306523....

On page 10, the 4 element, 7kW per element unit draws 58.33A per 60A breaker, 7000/240 = 29.167A, two elements a piece for 58.33A per 60A breaker.

It’s lot cheaper to wire up a 28kW electric heater if you have 480V three-phase, it’s only 28000/480/1.732 = 33.68A, all you need is a 35A 3P breaker, three #10s and a #10 ground.

240V single phase needs two 60A 2P breakers, four #6s and two #10 grounds, or if it was a single-point connection, one 125A 2P breaker, two #1/0s and a #6 ground.

Yeah, not worth it in most cases, but when things line up, it is the best.

I've built 3 houses and got a bid on ground source heat for each one. I finally pulled the trigger on the 3rd house because we:

1) Moved where it was quite a bit colder, -20F for a week is common. 2) We have enough land to trench only 6'/2m deep to bury the loops instead of drilling like we would have needed to do on the first 2 houses. 3) There was a tax credit on it 4) No equipment exposed outside

Absolutely love it and it will make it difficult to move away when we want to down size b/c we'll pay more in utilities for half the space.

We also have some air-source on an addition I built, I'd use it anywhere that was slightly warmer than where I'm at.