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How a heat pump works

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Re: How a heat pump works

#171

Post by thekingshorses »

achenatx wrote: post #96
boringg wrote: post #7

What is going on? Is there a global push to get everyone to switch to heat pumps. It seems that there is heat pump content everywhere. Clearly there is a push. I understand that its for climate benefits but it feels very coordinated. edit: didn't realize the attention I would get. Let me add someone answered my question -- a good product market fit and people talking is probably where the push came from. That said HV…

my friend is building his house and is putting in 4 heat pumps (big house). The problem is we just lost power for 4 days and 2 years ago we lost power for 5 days. He is discovering that electric heat uses massive amounts of electricity and there is no way to get a residential generator big enough to power them all. He might not even be able to power one (they can use in excess of 20kw). I would never get electrical w…

If there is a power outage, you can't run your natural gas heater either. It needs fan to run.

Re: How a heat pump works

#172

Post by bluGill »

boringg wrote: post #123
achenatx wrote: post #96

Earlier quoted context omitted.

my friend is building his house and is putting in 4 heat pumps (big house). The problem is we just lost power for 4 days and 2 years ago we lost power for 5 days. He is discovering that electric heat uses massive amounts of electricity and there is no way to get a residential generator big enough to power them all. He might not even be able to power one (they can use in excess of 20kw). I would never get electrical w…

So this is one of my big concerns - I live in a cold weather country currently. We have power outages once every couple of years. If I don't have back up power my pipes freeze and then i'm out probably > $50k. I was thinking the solution for me is to put in a heat pump and then run a backup gas generator. But that solution feels like a significant amount of overbuild. I have 3 minisplits already but they aren't valua…

Heat pumps are great when things are mildly cold. While do work down to -20C or so, efficiency drops off, so you need bigger and bigger units. It often makes sense to have a smaller heat pump that will only work down to -5C (random temperature, a real analysis of your house is required to give a better answer), and then a gas furnace backup for those really cold days. Once you have the gas furnace backup you can run that off of a small generator on the few days you are without power.

Re: How a heat pump works

#173

Post by notacoward »

mytailorisrich wrote: post #126
Thlom wrote: post #95

Earlier quoted context omitted.

I replaced my old air-to-air heat pump with a new one last year. Cost me in total around $3000-$4000. Might have been a bit more expensive if it was a completely new install depending on how it would be installed, but not too much more expensive. Might be more expensive in countries where you are using gas boilers as it sounds like your heating setup is much more complex than where I live.

Here in the UK, I think the cost of installing a new heat pump, bearing in mind that it's an installation from scratch, starts at about £10k ($12k as today's rate) to several tens of thousands. A ground source heat pump (which seem to be the ones pushed by the gov?) is probably £15k to £30k if you can install one at all. Replacing an existing gas boiler, which is what most people have, is probably around £2k or even…

FWIW, I just installed two heat pumps in a 3100sf house in the US northeast this summer. We already had ducted AC. The main unit was US$17K and the mini-split for the master bedroom was US$6K. There a US$10K state rebate, but we'll probably only get 70% of that because we've retained the old heating system as a backup and for water, so total cost is US$16K. These are cold-climate units, both rated down to -4°F but I haven't actually made them work below 20°F yet. Next year I'll probably set the aux cutover temperature to something lower and see how it goes. Year after that we'll probably install solar (plus wind if the technology for that has moved along far enough) and switch to all-electric everything.

BTW my town has an all-electric mandate for new construction already, and there's a lot of that. There's also a bylaw that takes effect in 2025/2026 banning gas-powered landscaping equipment.

Re: How a heat pump works

#174

Post by bluGill »

mikeyouse wrote: post #154
endemic wrote: post #114

Earlier quoted context omitted.

I don't understand why this is contentious. You're burning gas inside your house.

That's what is funny to me too -- they're basically phasing out all furnaces and hot water heaters that aren't direct vent (bringing in combustion air from outside) because it's so problematic to have gas-burning appliances in your home. Yet we just burn gas stoves -- some of which are massive without question... If you were to use all of the burners on this stove on their highest setting, it would consume more BTUs…

Most commercial stoves require a vented hood. Home depot may not tell you this, but the manual of the stove will.

Re: How a heat pump works

#175

Post by dsfyu404ed »

boringg wrote: post #7

What is going on? Is there a global push to get everyone to switch to heat pumps. It seems that there is heat pump content everywhere. Clearly there is a push. I understand that its for climate benefits but it feels very coordinated. edit: didn't realize the attention I would get. Let me add someone answered my question -- a good product market fit and people talking is probably where the push came from. That said HV…

> What is going on? Is there a global push to get everyone to switch to heat pumps. It seems that there is heat pump content everywhere. Clearly there is a push.

Based on the lack of political dick swinging I don't think this is a "push". They're legitimately good technology for certain use cases, I'm sure the manufacturers are pushing them. They are also The New Hotness(TM) and they are billed as environmentally friendly. Both those attributes are valuable by themselves to some people.

I think this is more a case of a grassroots-originated circle jerk within certain demographic bubbles.

I get a lot of "air fryer" vibe from the whole thing. And I say this as someone who owns and really likes his air fryer.

Re: How a heat pump works

#176

Post by bluGill »

kupopuffs wrote: post #166
rr888 wrote: post #140

I just dont like moving parts. My problem with heat pumps is that you have to replace every 10-20 years which seems wasteful.

Do you own a heater that has lasted more than 10 years?

The furnace in my house is from 1970 and still works. I don't want to know how inefficient it is. (I just upgraded the insulation of the house, replacing the furnace is a future problem)

Re: How a heat pump works

#177

Post by pjc50 »

redeeman wrote: post #44
boringg wrote: post #7

What is going on? Is there a global push to get everyone to switch to heat pumps. It seems that there is heat pump content everywhere. Clearly there is a push. I understand that its for climate benefits but it feels very coordinated. edit: didn't realize the attention I would get. Let me add someone answered my question -- a good product market fit and people talking is probably where the push came from. That said HV…

topic of discussion: is anyone else concerned that all the new things being clearly pushed hard, regardless of reasons(good or bad), has the common theme of centralizing. In a world where if your heatpump stops working, you die from cold, it would be an awfully sad thing if social credit scores dictated a very low kilowatthour limit. Much more sad than a world where you obtain firewood from some local vendor

> Much more sad than a world where you obtain firewood from some local vendor

A while ago I ran the numbers, and to meet UK electricity demand from wood would consume every single tree in the country in three months.

Limiting that to heating and giving up on industry would stretch that a bit, but the country is fundamentally dependent on imports to stay alive. We can't not be global.

Re: How a heat pump works

#178

Post by mikeyouse »

bluGill wrote: post #174
mikeyouse wrote: post #154

Earlier quoted context omitted.

That's what is funny to me too -- they're basically phasing out all furnaces and hot water heaters that aren't direct vent (bringing in combustion air from outside) because it's so problematic to have gas-burning appliances in your home. Yet we just burn gas stoves -- some of which are massive without question... If you were to use all of the burners on this stove on their highest setting, it would consume more BTUs…

Most commercial stoves require a vented hood. Home depot may not tell you this, but the manual of the stove will.

Apologies that link was broken -- but that was a "Commercial Style" stove for a home, not actually a commercial appliance. In any case vents are a really bad solution.. but they're inefficient at removing fumes, are usually undersized and too far from the cooking surface, and most people don't use them because they're obnoxiously noisy when running at the proper speed.

A friend of mine just remodeled their kitchen -- they got all the permits and sign-offs, and their AHJ allowed a gas stove in the island with no venting at all. Inspector told them they should open a window if they were doing a lot of cooking. It's actual madness.

https://i.imgur.com/ApCIyzS.png

Re: How a heat pump works

#179

Post by pjc50 »

mytailorisrich wrote: post #126
Thlom wrote: post #95

Earlier quoted context omitted.

I replaced my old air-to-air heat pump with a new one last year. Cost me in total around $3000-$4000. Might have been a bit more expensive if it was a completely new install depending on how it would be installed, but not too much more expensive. Might be more expensive in countries where you are using gas boilers as it sounds like your heating setup is much more complex than where I live.

Here in the UK, I think the cost of installing a new heat pump, bearing in mind that it's an installation from scratch, starts at about £10k ($12k as today's rate) to several tens of thousands. A ground source heat pump (which seem to be the ones pushed by the gov?) is probably £15k to £30k if you can install one at all. Replacing an existing gas boiler, which is what most people have, is probably around £2k or even…

I've just signed up to the Scottish government subsidized scheme for air source heat pumps, so I'll report back to HN on this.

Re: How a heat pump works

#180

Post by peterhunt »

boringg wrote: post #7

What is going on? Is there a global push to get everyone to switch to heat pumps. It seems that there is heat pump content everywhere. Clearly there is a push. I understand that its for climate benefits but it feels very coordinated. edit: didn't realize the attention I would get. Let me add someone answered my question -- a good product market fit and people talking is probably where the push came from. That said HV…

It is coordinated. In many states there are huge incentives [1] to disconnect your existing home from (and not connect new construction to) the natural gas infrastructure.

This is great for the climate but air source heat pump technology simply doesn't work well in cold climates. Most heat pumps in the United States have 100% efficiency down to about 20 degrees F. Below that they "lose efficiency."

What most people don't realize is that "lose efficiency" = blows cool or cold air. So if you live somewhere that routinely gets that low you are likely either going to be really cold, or have to engage aux heat (often natgas or oil-based heating or electric resistance heating).

Additionally, even when operating at 100% efficiency they don't blow air as hot as traditional heating sources. So if you have a poorly insulated room, large space, or even just an unusually cold day, it will often have a hard time keeping up.

I have found that I only use my air source heat pump a little bit during the fall in New England, and I have to run aux heat throughout basically all of winter. Talking to my friends in the region who have heat pumps, they all have similar experiences.

I think we are all very eager to get off of fossil fuels but the technology just isn't there yet, and I am concerned that most people installing heat pumps today don't know the risks associated with them in extreme weather events. If your heat pump can't keep up and you didn't install aux heating you can't live in your house, your pipes will freeze, and you will generally have a bad time. If you did install and use aux heating, you may be surprised at how expensive and inefficient resistive electric heating is as it may need to run all the time.

[1] Massachusetts will pay you $10k to install air source heat pumps and disconnect from natural gas https://www.masssave.com/en/residential/rebates-and-incentiv...

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