Heat pumps: what they do and why they’re hot now | Hacker News Reader

Heat pumps: what they do and why they’re hot now

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37 pointsTomte23 comments

I feel like it's almost a requirement to take this opportunity to share Technology Connections great video [1] on the topic.

Personally, I've used a heat pump as the sole heating unit for my house for the past 6 years or so. There have been a few cases where I've opted to use an extra blanket, but overall the results have been pretty impressive, and the cost savings are pretty huge. (Apartment, so no fuel heat, it's electric or nothing)

[1] https://youtu.be/7J52mDjZzto

Don't you find the background rumble of the air in the vents very enervating? I was in a friend's place with a heat pump, and I felt like I was inside a badly tuned organ. Lots of atonal near-subsonic rumbling. I think heat pump vendors need to learn about acoustics: standing waves, reverberation, phase interference.

That is not likely to having anything to do with being a heat pump. That is probably just the consequences of the blower, the length of ducts, how they are mounted, etc.

My two heat pumps aren’t too bad. The airflow is the same as the AC, meaning sound is present but no rumbling.

Is a heat pump any different from regular air conditioning in that regard?

I'm from an area of the country where you run the AC 8 months out of the year so this question is weird to me unless somehow a heat pump (reverse AC) is different than an AC pump running normally.

There are hydronic heat pump systems available as well.

This is so bizarre to me that heat pumps are just now being "discovered" by the US mainstream.

My old house that was built in 1979 had a geothermal heat pump which was a very new thing back then. Today Switzerland has the most heat-pumps per square meter than any other nation[1]. If you have the money here you get a geothermal heat pump and solar.

The fact that there is debate if they even work or they are ugly is ridiculous. The geothermal ones only require a small box in your basement[2] next to your boiler usually. The non geothermal units are cheaper but require quite a bit more space in your basement but you don't even need an outside unit as usually one window is used for intake an another for out.

[1] https://www.homegate.ch/c/en/advisor/living-and-furnishing/s...

[2] https://www.viessmann.ch/de/wohngebaeude/waermepumpe/sole-wa...

We’re getting air source heat pumps for our house in Michigan- including new tech that makes it still work to minus 20. However, due to the possibility of a polar vortex, and the decreasing efficiency below zero, the installer recommended a small backup furnace for the lower floor (the full electric backup option was electric heat coils, but that’s super inefficient). It will be interesting to see how often we choose to use that in practice.

The installer estimates I won’t save any money on energy bills during the heating season (like we would with ground source), but should be comperable. I also like that when we eventually get solar, we’ll be able to power our entire house (also getting induction stove).

Heat pumps are still a long way from the theoretical efficiency they could achieve.

For example, if I use a heat pump to cool my house down, and then later change my mind and use the same heat pump in reverse to heat my house back up again, in an ideal world I can get back all the energy I put in. (Assuming ideally insulated house)

With today's heat pumps, I get back nothing.

With in-the-lab prototype heat pumps I get back perhaps 1%.

But physics says I could get back far more if only we could get rid of the big inefficiency in every step of the process.

The main one being that every component of a heat pump becomes more efficient if it has smaller temperature differences between every component.

I don't understand the setup for what you describe in your second paragraph. Can you elaborate?

I’m not very fond of my heat pump. I really think our winters are a bit too cold for it, but I could see that changing if these new ones live up to the hype:

https://www.energy.gov/articles/doe-announces-breakthrough-r...

Can you say a little more about what you don’t like?

When it gets very cold, teens during the days and less at night- the heat pump runs constantly. It doesn’t help that the ductwork is in the attic. Eventually- after making the house colder then it was before it cut on- the ‘emergency’ heat will cut on and actually warm up the house. This ends up being very inefficient and expensive. It’s fine for mild winter days, but I question how efficient it’s being all things considered.

Thanks, we’re getting one installed and will have a small gas furnace supplement/ backup for the coldest days. Will be curious how the latest “hyper heat” tech works. They made it sound like we’d only need the backup unit on like negative 10 or worse days.

I live in Southern California and want to install a pool heater to extend the swim season (for my kids). I've been wondering how heat pump pool heaters compare to the more common natural gas heaters (both in terms of cost and effectiveness).

See the other comment with the YouTube video. He argues at one point that it's more efficient to burn the gas for energy and power the heat pump with it, then it is to use the gas for heating directly. I imagine that might hold for the pool too.

Though it would probably be a little less efficient since the water temperature would probably be higher than the air temperature inside the house.

The key with something like this is combining it with your house hvac. Assuming you have a heat pump based AC for your house (a safe assumption in so cal), you simply use the hot side of your houses AC heat pump circuit, heat that you normally just vent out to the atmosphere, and use that waste heat to heat your pool. Basically you put a heat exchanger where the radiator (hot side of the AC) was. Instead of putting the heat into the air through aluminum fins and fans, you put it into water flowing in copper pipes, then circulate that water into your pool.

This way you heat your pool for free (at least no more than you were paying before to cool your house). The bonus is that the heat exchangers with water sinks are super efficient.

I saw an episode of This Old House where they installed a setup like that: https://www.thisoldhouse.com/heating-cooling/21017234/how-to...

This company sells the product they're using: https://www.hotspotenergy.com/pool-heater/

It seems like a good idea to me, but from what I can tell it's quite uncommon (why?).

I think it's because the pool stuff is sold and installed by the pool people (with no need for a certified HVAC person), and the HVAC stuff is installed by a HVAC person with no need for plumbing. It's like why you get certain procedures from the cardiologist in the cath lab, and some procedures by a cardiac surgeon in the OR, sometimes the same procedure.

So cal gets cold?

It's all relative, right? It doesn't get cold enough to build a snowman, but it gets cold enough to make a 5 year old shiver in a swimming pool.

I am confused, I live in Florida and I have a big central AC system but it is also capable of heating. Is this not the same thing as a heat pump?

Yes, that’s a heat pump!

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