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How a heat pump works

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Re: How a heat pump works

#241

Post by rootusrootus »

notacoward wrote: post #173
mytailorisrich wrote: post #126

Earlier quoted context omitted.

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…

I think prices have spiked. Two years ago I installed a new heat pump to replace an old failing 5-ton air conditioner (which was paired with a high efficiency natural gas furnace; I kept the furnace as backup instead of relying on electric strips). It was $6K altogether. Was just going to replace the A/C with a new one, but the differential was $1500 and so I figured why not.

OTOH, a few months ago my stepmother installed minisplits after getting quoted $22K to install a whole-home forced air heat pump (going from no forced air at all, so part of that cost was ducting, though it's a single story ranch house so not terribly difficult).

Somewhere between those two points, prices went insane.

Re: How a heat pump works

#242

Post by Maxburn »

fullstop wrote: post #78
bcrosby95 wrote: post #64

Earlier quoted context omitted.

This hasn't been my experience. I can get an AC unit and gas furnace installed for something like 7k. But a heat pump unit that heats and cools is something like 13k installed. I obviously went with the former.

How long do those units last, though, and what is their operating cost over their lifetimes? TCO obviously includes more than the initial cost of the equipment.

Gas heat probably should be tuned up for clean burning every year or two. A heat pump is generally good for years until something breaks. Both systems need filter changes and coil cleaning, which most homeowners can do themselves.

Couple "fun" things about a heat pump; You will smell burning the first time the electric strips are used every year moving into the heating season, it's just dust burning off. Once you start moving into colder weather you might notice the system changing into defrost mode so it can melt ice off of the outside coils. There's a variety of sounds that accompany this and you might even see a bunch of steam coming off of the outside unit. It isn't smoke and it's normal. Every year there's a flood of 911 calls about this.

Re: How a heat pump works

#243

Post by scrollaway »

WatchdogReset wrote: post #231
YellowTech wrote: post #69

Seems like OP just performed a stress test on his website as he is the "Webmaster of https://hvac-learning.com an HVAC elearning website"[1]. Hopefully you can figure out something! Thank you for educating about such technology! [1] from WatchdogReset's profile about

I am sorry for the inconvenience. I am still learning how to build a nice and efficient website. I will analyze what happened and try to fix and enhance !

I love that you're building free educational resources, especially about something like this! If you need help/advice to help build your website, email me (see my profile), I'll be delighted to help pro bono. :)

Re: How a heat pump works

#244

Post by energ8 »

I have seen repeated claims of heat pump CoPs improving over decades. Can anyone summarize or provide links to what improvements are being made? Compressor technology? refrigerants? Fans to move heat? all of the above? Where is the path from here?

Re: How a heat pump works

#245

Post by rootusrootus »

trynewideas wrote: post #191
megaman821 wrote: post #91

Earlier quoted context omitted.

I assume in home that don't have ACs, that they also don't have ducts. Do these ductless homes filter their air, control home humidity, or bring in fresh air from outside?

Maybe a faulty assumption; my AC-less home has a ducted oil furnace, and we still haven't removed the ducts after installing a heat pump. Another house I lived in 12 years ago had ducts for oil furnace heating but no AC. Both were 100+ years old and in the northern US.

That matches my experience. All of our older houses around here with oil heat are forced air. Radiators are uncommon. But 'older' in this case is only 100-120 years.

Re: How a heat pump works

#246

Post by scrollaway »

ccooffee wrote: post #206
spikej wrote: post #199

Genuine question that I haven't been able to find a clear answer for: are heat pumps now different from air conditioners two to three decades ago? (other than the fact that they heat and cool) Memory is fuzzy but I remember when I was a little kid and even captain planet cartoon showed air conditioners being bad for the environment... Or is it that heat pumps are better than the fossil fuel counterparts and so if you…

> even captain planet cartoon showed air conditioners being bad for the environment That seems like it was a useful simplification for a children's cartoon, but things aren't that black-and-white. 1. Without air conditioning (or some other method of cooling and humidity control), almost all high-occupancy buildings would reduce their effectiveness as a work-place or living-place. OSHA has guidelines about office temp…

Are cooling blankets a thing? Like, a not-a-scam thing?

Re: How a heat pump works

#247

Post by guidoism »

titannet wrote: post #228
gabrielhidasy wrote: post #65

Earlier quoted context omitted.

They literally are more efficient than burning gas, a good heat pump can do over 300% efficiency (KWs of heat in your house vs KWs of electricity used) while a furnace can only hope to get 100%. Even if the heat pump is fed from gas power plants (which burn gas with about 50-60% efficiency, more if the waste heat is reused), they are still using less gas for the same amount of heat than directly burning it.

If that where there would be no discussion about the switch to heat pumps. But it isn't. In old houses (bad insulation, old radiators) and edge cases ("winter") heat pump are not just inefficient they may not be able to heat the house at all (unless extremely oversized). This is a huge problem in Europe where a house is expected to last a 100 years, in many areas much more.

Slightly unrelated, I have a friend who moved to the US from Mexico and was asking me about potentially buying a house. He started looking on Zillow with me and his reaction to houses build in the 1950s OMG how can it be that houses are that old and my reaction was wow that's pretty much a brand new house. He was blown away that a huge percentage of houses on the market are from the early 1900s and even late 1800s where we live.

Re: How a heat pump works

#248

Post by Casteil »

nly wrote: post #225
Casteil wrote: post #222

Earlier quoted context omitted.

He does, but he omits a lot of important considerations that make heat pumps impractical for normal Americans. If he touches on them, it's briefly - if at all, e.g.: - More expensive units, and more expensive to run power wise. It's always difficult to get adoption of new technology that's "better" but more expensive to buy & repair - to the point where RoI may never happen. - Power grid implications during very low/…

- Better than resistive electric heating for the grid. Gas is going away so this is a problem that has to be solved anyway. - Economies or scale will solve the repair and maintenance burden... hell, it's not like a gas boiler is maintenance free...fucking things requiring serving every year and break down all the time in the UK. - almost noone has a generator when the power goes out anyway. This is a very wealthy Ame…

- Sure, at least when it's not super cold. Electrical grid may be a "problem that has to be solved" but it's one that carries staggering price tags and will have to be gradually transitioned into over decades. Natural gas will likely still be used as a heat source for many well into the late this century if not longer.

- Gas boilers are far simpler units. Less moving parts, simpler electronics, all in all fewer points of failure than a cutting edge heat pump that can actually produce heat when it's below 20f (-7c, i.e. the only kind of heatpump that might stand a chance at heating throughout the cold winters most of the northern US gets).

- Be that as it may, heat pumps at this time are cost prohibitive - making them largely something only "wealthy Americans" can afford. Many people still run old 80% efficiency units because of similar reasons to boilers: they're cheaper, simpler, and less likely to fail.

Re: How a heat pump works

#249

Post by WatchdogReset »

jcstauffer wrote: post #5
WatchdogReset wrote: post #2

The heat pumps are one of the means of heating (and air conditioning) in the heart of the news. What is their principle of operation. You can ask questions here if there are points to clarify in the course

I'd like to get a heat pump to replace my existing baseboard hot-water system (currently powered by an oil furnace) without converting to a heated air system. From what I've read, that's not quite feasible yet, since current systems can't produce a high enough temperature. What are the prospects of that technology becoming viable in the next few years?

As others comments said, it depends on the climate : The problem is that the power/performance of the heat pumps decreases with the cold weather and the necessary increase in the temperature of the heating water, which obliges to keep the boiler for the cold weather. This is a problem for the heat pumps without probable solution and little progress to wait. The solution is to insulate the house very well so that its needs can be covered by the heat pump with less hot water. Divide the losses by 2 at least.

Re: How a heat pump works

#250

Post by elil17 »

nashashmi wrote: post #113
pjerem wrote: post #50

Earlier quoted context omitted.

Yes they are. You get more heating from an heat pump running from electricity coming from gas plants than what you get by just burning the gas. Including losses on the grid.

I cannot imagine this in anyway. Heat pumps work like ACs do. They do compress a medium till it heats up, and then spread that heat around. And then they decompress until it cools down and dump that cold until outside heat brings up the temperature again. Those compressions and decompressions take up immense amounts of energy. They are less efficient than simply burning gas. On the flip side, could we not create elec…

I think you are misunderstand where most of that energy comes from. Say I have some refrigerant in liquid form at a low pressure. That refrigerant will have a boiling point of say, -20 degrees F. I use the ambient air, which is say 0 degrees F, to boil the refrigerant into a gas. The internal energy of the refrigerant goes up significantly, but it's temperature does not change. Then, I compress the gas so that it goes up in temperature. This change in temperature does not correspond to a large change in the internal energy of the gas. The same energy is pushed closer together, resulting in a higher temperature[1]. Then, I condense the gas at it's new boiling point, say 100 F, into a liquid. Then you decompress the resulting liquid and the cycle repeats.

Most of the energy is coming from the ambient air, only a small amount of electricity is used to change what temperature that energy is available at.

[1] A very simple mental model you can use to understand the difference between temperature and energy for a gas is that temperature is the number of times the gas molecules bump into each other in a second, while energy is how fast the gas molecules are moving. So if you have a very low pressure gas, even all of those molecules have a ton of energy in the form of motion, the temperature of the gas will be quite low because the gas molecules won't interact often. But compress that gas down to a small volume, and the molecules will bump into each other all the time even though they don't have much more energy.

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