A lot Heat Pump Thread

[jyl]

Have we discussed heat pumps for houses?

How well they work in colder climes, what subsidies are available, their use for cooling as well as heating, different form factors, types and brands, other pros, cons, and considerations?

I did use the search tool but didn’t find much discussion.

[Paul T]

Originally Posted by jyl

Have we discussed heat pumps for houses?

How well they work in colder climes, what subsidies are available, their use for cooling as well as heating, different form factors, types and brands, other pros, cons, and considerations?

I did use the search tool but didn’t find much discussion.

I'm not an expert, but I don't believe they work well in colder climates at all, esp. below freezing. Most are paired with electric heat backups for when it gets too cold. I almost never see them in the NE, outside of a utility building that doesn't get year round usage.

[Tim Hancock]

I installed Bosch mini split system in our house early last summer. My units are rated to still provide heat function down to -13 F outside temp. We have had a relatively mild winter here in NW Ohio so it only got down to -5 once or twice. It still worked for us on those nights. Bosch has more expensive units that can operate in even colder temps, but we did not choose that option as -13F seemed fine for our climate.

We have ceiling and baseboard heating in our 60's split level home and only had window type air conditioners until we went to the new mini split system. It has worked perfectly thus far in both summer and winter. It supposedly is much more energy efficient to operate than our old all electric heat and window AC units. That said, we still have our old heat system and if temps ever got below the -13 f rating of the mini split system, our old system still works.

My wife pays our electric bills and I have never taken the time to compare usage from past years. With this mild winter, the numbers wouldn't mean much anyways this first year into it.

[Bill Verburg]

In the fall I installed a dual Lennox system, heat pump and gas furnace, i choose the most efficient models available at that time.

The heat pump does work at least down to ~20F, but while not as noisy as the old AC in the summer still makes a lot more noise than the gas furnace.

strike 1

The cost of gas here is much less per therm compared to electricity, so i programed the heat pump to only come on in the 50s and up for heat.

strike 2

The gas furnace makes almost zero noise, It's unbelievably quiet, so even if the price per therm was comparable, I'd use gas.

strike 3

Haven't run it through a cooling season yet but I suspect that it will be a better choice than the older Ac system was.

The system was expensive but there was a considerable benefit in rebates and tax credits that took a lot of the pain away.

[peppy]

In humid areas they can build up mold and mildew on the fan, and it's a pain to clean.

[Norm K]

We have a heat pump system: although it doesn't get nearly as cold here as it did when we lived in Colorado, the system has had zero issues keeping our 4K sqft home warm when temps drop into the mid-teens.

And FWIW, it does its job admirably during the North Carolina summers as well.

_

[greglepore]

There are specific inverter driven cold climate heat pumps. Fairly new to the market and very efficient. Fujitsu and others. "Normal" heat pumps require some form of either resistance or gas/propane heat when its below 40 or so-my older system uses propane hot air as back up for the main system, elect resistance for the smaller.

[RANDY P]

Put a dual stage Trane in last summer to replace my single stage in AZ.

Got a good energy credit, power bill went down significantly over the old original single and best thing is it regulates the temps inside the house much, much more consistently.

With the old system when the AC kicked on you would freeze to death while blowing, temp goes to setting. Heat climbs, AC kicks on, freeze to death, temp goes to setting. now it stays close to a consistent temp- and you don't hear the fan anymore since it's going at a lower speed much of the time.

Much better energy efficiency, tax benefit, better climate control, quiet.

Just, better.

[jyl]

I had planned to install mini-split AC units in the upstairs bedrooms, where the central AC doesn't cool effectively (small ducts, no returns).

Now I'm thinking I should make those mini-split style heat pumps to both cool and heat those bedrooms. The main forced air gas furnace doesn't do a good job of heating those rooms.

The idea being that the main forced air gas furnace and central AC would then only be used to heat/cool the ground floor, which it does well (larger ducts and returns), while the heat pumps would do the job of heating/cooling the upstairs. At night I could program the main furnace to hold the ground floor at a chilly temperature, while the heat pumps keep the occupied bedrooms warm, and the unoccupied bedrooms are not heated.

I want to keep the gas furnace because I can run it on a generator when we lose electricity, which happens (occasionally, but can be for days at a time) in the winter. I am not willing to go "all electric", partly for power outage reasons and partly because our electric utility is raising rates like crazy (+20% this year). I wouldn't need the heat pumps to work well when it is very cold outside, since we can always crank up the gas furnace during those periods, although it would of course be nice if they did.

[rwest]

Recently put in a Bryant mini split in the garage to replace a small ceiling hung electric heater.

I put my amp meter on the old heater and it pulled 20 amps when running. The highest I saw on the mini split was 13 amps, but usually it is running 4-8 amps.

Hard to really compare the two without doing some sort of data logging as the old heater put out around 300 degrees F while running and the mini varies from slightly above room temp to 130F.

Also the mini’s lowest temp is 60 degrees and I used to set the old one at 53 degrees.

Bonus is that I now have AC in the summer!

The unit I chose is supposed to still heat at -20F not sure what kind of devil wizardry is going on to still scrub heat out of those temps!

[pksystems]

They were failing like crazy around here in the last cold snap.

[JackDidley]

I have a heat pump and a gas furnace. The heat pump works good down to about 30°F but the blower noise bothers me and it runs a lot longer than the gas furnace so below about 40° and I just switch to gas for the winter. Small house so the heat cost is pretty low anyway.

[rwest]

Originally Posted by pksystems

They were failing like crazy around here in the last cold snap.

My manual actually states that in very cold weather that supplemental heat will likely be needed. I am leaving my ceiling heater in place as a backup.

[rfuerst911sc]

About 4 years ago I had a Goodman dual fuel heat pump/furnace installed . It is an 18 SEER with LP furnace . It is a conventional heat pump vs inverter . Here in north Georgia it is a good way to go .

At 39 degrees or colder the LP furnace is used . Above 40 the heat pump is used . The unit we replaced was also a dual fuel but only 10 SEER . Our electric bill dropped like a rock with the newer unit . I have no complaints .

In my 24 x 26 man cave garage with 12 ' ceiling height I have a 24k Mitsubishi mini split that is 24 SEER . That unit is VERY efficient and I have yet to have a cold temperature where it didn't produce heat . But the coldest we have seen was about 20 degrees . On the flip side we have seen 100 degrees in the summer and it cools great .

If I was ever to build a house I would specifically build with mini split in mind . A single outside unit can run multiple indoor heads . I think that may be the most efficient way to heat/cool without going Geothermal or similar .

[beepbeep]

We installed 8kW thermal power ground source heat pump here in Sweden 11 years ago. Never looked back. We use 170m deep borehole as heat exchanger. Only issue we had was one worn out brine pump. It works fine and is able to heat the house to 22 degrees C when it is -20 degrees outside. It draws around 1.4kW of electricity (depending on if it is heating tap water or the house).

It is docked to underfloor heating to maximize COP (heat pumps do not like high temperatures).

[billybek]

Some good points already made here, particularly about ground source heat pumps. They produce pretty much the same amount of heat regardless of the outdoor temperature so they are an attractive (but more expensive) method of extracting heat from the great outdoors as outdoor ambient temperature drops.
Heat pumps with an outdoor air over unit are much more effective now those made 10 to 15 years ago. They can produce heat down in lower outdoor temperatures more effectively than in the past reducing the requirement for back up heat.
That doesn't (in my opinion) mean that their efficiency doesn't suffer as outdoor temperatures drop. They eventually will reach a balance point where the heat required equals the heat lost from the home requiring the unit to run all the time. Their efficiency also drops as outdoor ambient temperatures go down.
That may not be a huge deal to have the system not cycle. Part of the new control strategy for heating and cooling is to have the system cycle less often, reducing energy required to start the compressor.
In very cold climates, like where I live, a ground source heat pump would be more effective albeit a much more expensive first cost to install.
My 96% efficient gas furnace will be my choice to provide heat for quite a while longer.

[flipper35]

We have a ground source as well. Never an issue with heat or cooling. Paid for itself in 7 years even though we had to horizontal bore and improve the size of the ductwork. Cooling costs are especially attractive in the humid summer here in SW WI.