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Heat Pumps – The Well-Tempered Future of A/Cs

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Re: Heat Pumps – The Well-Tempered Future of A/Cs

#331

Post by kelnos »

rapjr9 wrote: post #272
aurizon wrote: post #92

These gradient comfort guys want $5000 for an 8000 btu unit with a total weight of $150 pounds. Compressor and heat exhaust hand outside. Evaporator and fan/control hang inside, It has a SEER rating of 10. There are dozens of minisplits for $1000 that have a SEER from 19-24. I can see no reason why a close coupled mini split with a 1" armored electrical/freon joint could not be made. This is what a gradient comfort i…

This seems to be a much more reasonable unit, 10,000 BTU, does both heating and cooling via a heat pump, and it costs $700, although there are a lot of negative reviews: https://www.amazon.com/dp/B09ZCZSSV8 $5000 is ridiculous for the Gradient Comfort 8000BTU window unit. The Soleus is the only other heat pump window unit I've seen for sale. Midea makes some A/C's that are more efficient because they use an inverter,…

It's that cheap because it's garbage. All the 1-star reviews (26% of all reviews) I looked at said various variations on the unit failing after some small number of months, and the return/replacement process is awful.

Seems like the manufacturer just makes junk and hopes they can still keep the money by making it hard to return.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#332

Post by tcfhgj »

Alupis wrote: post #314
tcfhgj wrote: post #242

Earlier quoted context omitted.

Heat pumps power consumption can be modulated by energy providers and improve grid power stability. In Germany you get way cheaper electricity prices if you allow this.

I am not aware of any such system in the US. What do you mean by "modulate"? Your utility provider decides how much heat your home gets? That's a very strange concept.

No, they decide how many energy the heat pump currently uses for heating.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#333

Post by jillesvangurp »

rayiner wrote: post #129
jillesvangurp wrote: post #97

Earlier quoted context omitted.

This persistent myth just needs to go away. People use heat pumps all over Scandinavia, including in the arctic circle. They are extremely popular there. They were early adopters of this technology there decades ago. There are two popular varieties: - Ground source heat pumps. Those work pretty much anywhere; just dig below the perma frost and you are good to go on the northern tip of Canada, Alaska, Norway, or where…

The myth exists because the US is probably 10-20 years behind Europe and China in terms of HVAC and insulation technology. I recently had some reasonably high efficiency heat pumps installed at my house, and I’ve been very unhappy with the low temperature performance. It doesn’t even get very cold here—rarely below 5F (-15C) and a record low of -8F (-22C). The heat pumps I got (recommended by the well-regarded local…

Sounds like they undersized your installation in order to quote you a lower price. The efficiencies of heat pumps are well documented as are the weather patterns in your area. So, they should/could have known better.

Two solutions to this problem:

1) get a bigger/better heat pump.

2) improve you building insulation and figure out where you are losing energy.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#334

Post by Tor3 »

__MatrixMan__ wrote: post #15

I live in a colder climate where heat pumps are not popular. After talking with a number of HVAC people about this I was surprised to learn that despite being very similar to an AC system in principle, in practice converting an AC system into a heat pump system doesn't make economic sense--you end up just ripping one out and installing the other. I don't fully understand why this is the case, but I hope that there's…

Colder climate is exactly where you want to use heat pumps. The numbers for Norway in 2022 (https://www.novap.no/om-varmepumper) is 58% of Norwegian homes (houses) have a heat pump installed, 34% in service industries, 8% in other industries. For homes air-to-air dominates (more than 90%). And since then this has just increased even more (and older heat pumps are being replaced with newer and better ones as well).

As an aside, many have commented on the claim that heat pumps make more sense with a well insulated building, arguing that it should be the other way around. The reason that you do want a well insulated building is simply that air-to-air heat pumps are limited to typically less than around 8kW heating capacity, and with a well insulated house you can heat a large area with that, with bad insulation you can't, and you would need a much more expensive type - typically not those sold to home owners (or buy several pumps, exploding the costs). In addition to that, a heat pump is more efficient when it doesn't have to run at maximum capacity. The heat pumps sold in the Nordic countries are typically around $3000 including installation. And they're highly efficient.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#335

Post by doikor »

SkyPuncher wrote: post #219
shusson wrote: post #204

Earlier quoted context omitted.

Yes modern day a/c is usually a heatpump. I’ve noticed a lot of people misunderstanding heat pumps, and thinking it’s some sort of replacement for A/C. Or that heat pumps are some new tech.

The key difference in modern systems is the variable speed control and two way operating.

And different gas/liquid allowing operation in much colder environments.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#336

Post by Tor3 »

bfuller wrote: post #166
Alupis wrote: post #140

Earlier quoted context omitted.

Natural gas is available in abundance, is nearly free in terms of cost, and is vastly more "green" than many alternatives available today. It may not be as green as pure electric can be in theory, but in large portions of this country electric isn't all that green either. Heat pumps appear expensive to operate. Imagine running your AC year-round... that very thought makes many-a-homeowner shudder.

Heat pumps are expensive to operate, and a nightmare to fix. There is a big movement to build whole subdivisions without using natural gas at all, electric ranges and heat pumps. I don't know why it upsets me so much but it does.

Heat pumps for homes aren't expensive to operate. They are cheaper to "operate" than resistance heaters. I doubt they're a nightmare to fix - I have actually had to get mine "fixed" once. It was still fairly new, and it turned out there was a leak in the tube so the coolant gradually (over the last year) got out. The company came and fixed that easily enough. Since then (January 2011) the heat pump has been running 24/7 with no issues whatsoever. In fact you're not supposed to turn them off at all, the moving parts are supposed to keep moving. So, if I'm away for some weeks I simply set the temperature to the recommended "idle" temperature of 17C, which in practice means it's not really doing any work, but it's not off either.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#337

Post by Tor3 »

Alupis wrote: post #226
cycrutchfield wrote: post #197

Earlier quoted context omitted.

Induction cooktops heat faster and more evenly than gas

There's many good reasons induction cooktops aren't used in commercial kitchens... and those reasons apply for home-cooks as well.

But they are used in commercial kitchens. I joined a cooking course arranged by a well-known restaurant where I live, and to my surprise the kitchen we used used induction. Very easy to operate, and you could easily set the heating exactly. It worked basically as a gas restaurant kitchen, just without the gas.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#339

Post by _fizz_buzz_ »

staplung wrote: post #324
nsxwolf wrote: post #193

When I needed a new air conditioner a couple years ago I was quoted $17,000 for a heat pump. I can only guess at that point whatever energy cost savings it would bring would never be realized within the service life of the system. I went with a $6000 standard replacement AC unit.

Might have been what I call a "fuck off" quote. That is, the people who gave you the quote didn't really want to do the job (too small, inconvenient location, or who knows what) and so quoted you an outrageous price figuring you'd either decide not to do it or if you did, you'd end up paying enough to make it worth their while. Happened to me a few years ago when I needed to re-tar my roof. The first guy quoted a fig…

Not a handy man, but we build power electronics and a lot of customized stuff. I also often give quotes that are really high for stuff that we don't actually want to do. It's kind of better than saying we cannot do it (because then they will never ask again) and if they agree to it we make a lot of money. For larger investments it makes sense to get a second quote.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#340

Post by kbuck »

stephen_g wrote: post #316
lsaferite wrote: post #184

Earlier quoted context omitted.

I've seen heat-pump base water heaters, but never a clothes drier. That sounds interesting. Now I have something new to research, thanks! Personally, I'm always curious why there isn't a more unified heat-exchanger system built into the structure of a house. HVAC, Water, Refrigerator, they all need to move heat from one place to another, why not work together?

I've tried to make the idea work in my head many times but my conclusion has been that I don't think there's quite enough co-incident demand for heating and cooling in the average house. For example, yes, I could generate all my domestic hot water from heat from air conditioning in summer, but in winter I need to be able to generate it plus heat the house, so I need enough capacity to generate that heat from the outs…

I think the big issue is the different "tuning" for each heat pump system. For example, a heat pump water heater needs a different maximum temperature than an air conditioner, and has much different cycling behavior. This leads to very different design decisions, including refrigerant choice, pressure, compressor type, whether the refrigerant loop is even serviceable, etc. (Some appliances operate at a refrigerant pressure so high that they require being fully assembled at the factory, which would be a non-starter for a manifold system like we're discussing.)

I think this might eventually become a thing once science gets us far enough that there's an "obvious" refrigerant choice for most applications, but we definitely aren't there yet. There are hundreds of different kinds that perform better or worse in different applications.

AFAIK all of the big commercial systems that do multiple different types of heat transfer use water to do it, thus bypassing the entire refrigerant selection issue. Right now the most advanced we can do is VRF ("Variable Refrigerant Flow") systems that can individually select air handlers for cooling or heating (i.e. move the heat from one room to another). These are still commercial units and not really available for residential installs.

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