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How a heat pump works

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Re: How a heat pump works

#191

Post by trynewideas »

megaman821 wrote: post #91
oceanplexian wrote: post #85

Earlier quoted context omitted.

An overlooked benefit is that they actually improve comfort over a boiler in a dry climate, so if you live somewhere with low humidity they help keep the air less dry. They also give you heating and cooling.. for places that don’t have Air Conditioning it’s a worthwhile upgrade.

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.

Re: How a heat pump works

#192

Post by mataug »

boringg wrote: post #187

Oh I have a question for the community here about heat pumps. I have three mini splits that I use for AC but connecting them to a home hub is bananas amount of work and inconsistent (Mitsubishi brand). I wish there was a legitimately good, robust system to connect AC units to my smart thermostat (Ecobee) or even some of the other devices I have. It still feels the wild west for home energy systems - and the costs are…

So far I've been happy with using the mysa ecosystem for my smart home. It works with Apple HomeKit, its had relatively good reliability and the team behind the product have been responsive when I do face issues.

https://shop-us.getmysa.com/products/mysa-ac

From a technical perspective its just a IR remote with a wifi connection and a touch UI, but for controlling mini-splits it works great in my home.

Re: How a heat pump works

#193

Post by kortilla »

mikeyouse wrote: post #178
bluGill wrote: post #174

Earlier quoted context omitted.

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 --…

“Solution is bad when you don’t do it!”

Re: How a heat pump works

#194

Post by PaulDavisThe1st »

jjtheblunt wrote: post #12
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…

Wait till we have Heat Pumps built with Rust! But seriously i think it’s just that awareness hit a critical threshold so the hysteresis kicks in and articles proliferate. In both cases.

There's really no question that Rust will undoubtedly take over most heat pumps, sooner or later.

Re: How a heat pump works

#195

Post by aintgonnatakeit »

oceanplexian wrote: post #85
wongarsu wrote: post #27

Earlier quoted context omitted.

For a long time the main problem of heat pumps was that while they are more efficient, a kilowatthour of gas or oil is much cheaper than a kilowatthour of electricity. But in the last two years natural gas prizes have gone crazy, removing that price disadvantage. Of course heat pumps emitting no particulates and being able to run on renewables are also good reasons, especially as the health impact of living in cities…

An overlooked benefit is that they actually improve comfort over a boiler in a dry climate, so if you live somewhere with low humidity they help keep the air less dry. They also give you heating and cooling.. for places that don’t have Air Conditioning it’s a worthwhile upgrade.

Sorry but this is incorrect. Boilers aka hydronic heat is usually delivered through baseboard fin-tube or hot water radiators. These heat mostly through convection with some radiation. Any humidity in the house is retained. Forced air heats the air and removes humidity absent a humidifier.

Re: How a heat pump works

#196

Post by LazyMans »

fullstop wrote: post #164
notyourwork wrote: post #155

Earlier quoted context omitted.

The constant running also affords a more consistent temperature because air is continually moving. Decreases the temperature variance throughout the zone. I have a 3 zone heat pump, 2 single room zones upstairs and a main floor with a air handler. We LOVE the setup so far.

Yes, I've been happy with ours and it was a great improvement over the last heat pump that we had. Habits are hard to break, though, and there's not much value (if any) of lowering the set-point at night during the winter months. People still do it, though, and then the unit is working overtime in the morning to reach the desired set point. I'm glad that you're happy with your setup!

Just to clarify, it is more efficient to lower the set-point in the winter over night. The issue is when your thermostat is set to utilize aux heat if the delta is higher than your set point change in the morning. For example. If you change from 70 to 67 at night. In the morning when the set point goes back to 70, the thermostat is likely configured with an aux delta of 2 or 3 degrees. Meaning every morning the expensive resistive heater is running to raise your temp quickly.

Personally, for my home and climate in the area, I disabled aux heat entirely, unless the temperature is below 0f outside, or if it hasn't reached the set point within 2 hours. Recently had some cold weather and these settings worked well for my home.

I'm using an Ecobee, configurations will vary per thermostat. The big settings for me were using manual staging to configure the temperatures to engage aux, temps to lock it out, etc.

Re: How a heat pump works

#197

Post by kodt »

gwbas1c wrote: post #53
Bhilai wrote: post #26

Definitely a lot of posts about heat pumps on HN recently that this topic has piqued my interest but only to the point that I want to know if I can install one in my home. Are there any legit resources out there that can help me understand if heat pump is a right choice for my home based on Geo, type of home, sqft and other factors to consider before replacing current systems (two ACs and two furnaces?)

Generally, they can work anywhere in the continental US. (Assuming you live in the US.) If you're in northern NH, NY, VT, or Maine, you might want to keep your gas system as a backup. (New homes tend to have electric backup, but if you have an older home they just keep your furnace as backup.) I have a 3000 sqft house in MA with a heat pump as my primary heat, and an electric strip as backup. The heat pump goes into…

North Dakota and Minnesota are on average colder than the states you listed. I would also include Montana, Wisconsin, Wyoming, and Idaho as states where you should be concerned about performance in sub zero temperatures and have a backup heat source.

Re: How a heat pump works

#198

Post by steve76 »

gabrielhidasy wrote: post #65
nashashmi wrote: post #16

Earlier quoted context omitted.

They are not more energy efficient than burning gas. Edit: since i am getting downvoted to oblivion, let me fight back here. I genuinely wished heat pumps would be more efficient and in theory they can be. I would love to not generate heat and just use the outside heat energy and compress it down into a smaller location. But compressing and decompressing is not an energy efficient task. It takes a lot of work. Mechan…

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.

[dead]

Re: How a heat pump works

#199

Post by spikej »

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're going to do something bad you might as well do something less bad?

Re: How a heat pump works

#200

Post by danans »

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…

> 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).

If he's building the house new, he should strongly consider investing in designing the building envelope in a way that 20kW heat pumps aren't required. It's very possible, especially with new builds.

The models to follow are Passive House [1] and Pretty Good House [2]. There are many examples of large houses built to those standards in cold climates that use a heat pump that only draws 2kW, which could easily be powered by a generator or backup battery. This assumes that by "big house" we mean something still below ~3500sqft and not some kind of mansion.

The basics are to get the building air leakage below 1ACH50 (3-5x better than most codes, but not hard in a new build), and eliminate thermal bridging by using thick exterior insulation around the building perimeter.

1. https://passivehouse.com/

2. https://www.prettygoodhouse.org/

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