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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

#211

Post by nerdbert »

samtho wrote: post #49
cyfex wrote: post #5

Earlier quoted context omitted.

I have never really understood the difference between a heat pump and an A/C myself. Any expert care to explain it in layman's terms?

An A/C works almost identical to your refrigerator. Using a closed loop of refrigerant with specific thermal properties, it will remove heat from one side and emit heat from the other. If you are able to run this system backwards, you could in theory swap which side is a heat sink (the cold side) and heat source (the hot side). While a traditional A/C cannot do this, heat pumps can electronically switch which side of…

> Fun fact, a resistive heating device is a rare case of something being 100% electrically efficient in that all the energy it uses will be turned into heat

My understanding is that you get considerably more heating per watt-hour with a heat pump than with resistive heating, though. I get that it's not creating that heat but moving it, but still that seems like even more efficiency from the perspective of energy consumption per useful heat made available.

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

#212

Post by fireflash38 »

Casteil wrote: post #165
web3-is-a-scam wrote: post #130

My 20 year old air conditioner recently died and I was looking into replacements. In my climate the temperature ranges from 40C in the summer, and -40C in the winter. After doing some research, it seemed pretty clear that having a furnace+AC was the way to go for my climate. Hardly a magic bullet technology.

Similar climate here, although days it gets below -10f / -23c are uncommon. Most winter days in a climate like this you could heat with a modern/high tech heat pump, but: - It's probably going to be more expensive than heating with natural gas if you're in the northern US - at least as things are today. - A modern/high tech heat pump capable of heating when the outdoor temp is - A natural gas furnace can keep you war…

> I'd still go with a heat pump AND gas furnace for backup though.

Thankfully, this isn't too expensive of an option to do. Gas furnaces are cheap. Heat pump that isn't sized to go to -40F/C is also pretty affordable. The crazy high SEER ratings drive up the price.

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

#213

Post by nerdbert »

usrnm wrote: post #145
nielsbot wrote: post #132

Earlier quoted context omitted.

-40C? That's an extreme situation. Heat pumps can be installed with backup heating as I understand it.

> That's an extreme situation Depends on where you live

A vanishingly tiny percentage of the world population lives somewhere that regularly reaches -40°.

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

#214

Post by xattt »

chongli wrote: post #206
SECProto wrote: post #198

Earlier quoted context omitted.

What kind of a system were you installing? We had a heat pump installed three years ago for less than $5k Canadian. Can't remember if we got a rebate on top of that or not.

We got a system for around $10,000 Canadian. But then there was a $5000 rebate. These things are quite expensive. I think the HVAC installers are making a large commission though. The actual equipment costs much less than that.

I have a sneaking suspicion that green rebates are being exploited by historically shady businesses (contractors and car dealers) by baking in the cost of the rebate into the final price.

There’s a local lot with a used 2021 Ioniq with the usual “used car dealer” hand-lettered sign proclaiming the $5,750 provincial rebate. I’m also fairly certain the car had its price inflated by that much by the dealer, or will climb by that as soon as negotiations start.

(1) https://www.apexautogroup.ca/inventory/2021-hyundai-ioniq-el...

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

#215

Post by mindslight »

triceratops wrote: post #167
mindslight wrote: post #123

Earlier quoted context omitted.

> Air conditioning is a heat pump and can achieve up to 300% efficiency. Whereas most houses in cold climates use furnaces, which have at most 98% efficiency. No. You can't directly compare "efficiency" numbers across different energy sources. My understanding is that the efficiency of gas powered electricity generation is around 33%, meaning that powering a heat pump with a COP of just under 3 will be of similar end…

End-to-end efficiency calculations are tricky and depend on a lot of variables.

Sure, but that doesn't mean you can throw your hands up and make an argument comparing nameplate efficiencies of things with different energy sources.

I'm well aware the figure in my above comment could be off by a decent amount due to transmission efficiency, what specific plants are generating marginal power, etc. But it's at least framing the comparison right.

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

#216

Post by fireflash38 »

amluto wrote: post #205
rayiner wrote: post #129

Earlier quoted context omitted.

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…

In my local market, if you ask an installer for a heat pump, you get something from Japan or Korea. I’ve never encountered an American unit. (I’m referring to normal air-to-refrigerant-to-air heat pumps. I know of a really weird system that is thoroughly American and an utter pain in the arse to replace because it’s specialized and undocumented. It’s quite loud, too, because it’s single-speed, and that single speed i…

Trane and Carrier are both US based and do heat pumps. They are more expensive than Mitsubishi or Daikin though.

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

#217

Post by hattmall »

zamalek wrote: post #155
pdx_flyer wrote: post #152

I was looking for a whole home heat pump and got some quotes that started at $27,000 for a home that is 1800 square feet. That price is a bit hard to swallow. I really don't want to just cool one or two rooms in the house.

Are you sure you aren't getting quotes for a ground-sourced (AKA geo) heat pump? We just installed a 4.5 ton (overkill for your sqft) 20 seer unit for $18000.

That seems crazy high too though, I just got a 5 ton for a 2300 sq ft house with 12kw heat strips including duct work for 10k. The duct work was $3800.

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

#218

Post by SkyPuncher »

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.

That must have included furnace replacement components for cold weather (e.g electric heat strips).

Otherwise, heat pumps are essentially the same as modern A/C units.

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

#219

Post by SkyPuncher »

shusson wrote: post #204
nottorp wrote: post #3

Isnt any a/c a heat pump though?

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.

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

#220

Post by out_of_protocol »

Moto7451 wrote: post #9
nottorp wrote: post #3

Isnt any a/c a heat pump though?

Compared to a traditional air conditioning unit, the reversing valve is the major difference. Your standard AC can only move heat from indoors to outdoors. A heat pump can do the reverse to warm your space. My basement heat pump is rated to provide heat even when it’s -20F outside.

I think any and all AC units sold in europe (split systems with inside and outside module) can do heating and cooling just fine with great efficiency. Many models rated to work at -20C, sometimes -30C
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