3 ms·

Almost certainly. Proper/modern heat pumps do not need heat strips until -20F or so

tharkun__ 3y ago
Agreed. Ours is at least 5 years old if not more now and was way cheaper. That said there is a difference between mini-split and something you hook up to internal ducting where your furnace used to be and prices have increased in the meantime. That said there was basically no difference in putting in an A/C only unit vs a combination. Technology wise it's the same so to speak just running in reverse in winter vs summer. We use the heat pump down to -15C-ish then I usually shut it down and just use the baseboard or if awake the stove (looks much nicer ;)) It was a no brainer to get the combination unit really. I don't get why it isn't the default nowadays and A/C and heating are thought of as separate concerns. We just don't have ducting, else we could A/C the whole house vs. just one floor.
- sokoloff 3y ago
  Mechanically, there’s a reversing valve and defrost elements and controls to turn an AC into a heat pump. (So, it’s small, but not zero, mechanical differences.)
  - tharkun__ 3y ago
    Thabks for the assist on the tech! And I can definitely attest to the heating element aka defrost. We don't have actual resistive heat in the pump as we have the baseboards anyway but the lower the outside temp goes the more it has to defrost the outside as it freezes up. As winter goes by, icicles form underneath the outside unit where the defrosted ice drains out and refreezes. It's actually amazing that the thing can extract heat from -10C air outside to heat up air that's already 21C inside to heat it up even further!
- throw0101a 3y ago
  > That said there is a difference between mini-split and something you hook up to internal ducting where your furnace used to be and prices have increased in the meantime. Generally true, as the mini-splits (have) tend(ed) to operate down to lower temperatures, but the heat pumps that look like 'traditional' outdoor A/C units are getting down there as well: for example this Lennox unit can work down to -4F / -20C: * https://tech.lennoxintl.com/c03e7o14l/viu12ch2uv/ehb_sl25xpv_2109.pdf https://tech.lennoxintl.com/c03e7o14l/viu12ch2uv/ehb_sl25xpv... That'll provide pretty good coverage of the year in many parts of North America before something like a gas furnace needs to kick in. (Speaking as someone who lives in Canada.)
rayiner 3y ago
They need them installed (and the extra dedicated 240v outlets, which can get expensive) for defrost cycles which happen below 35F or so.
- xyzzyz 3y ago
  Depends on whether they are reversible or not. Reversible ones, which can act as AC in summer, simply reverse themselves and act briefly as AC, essentially using heat taken from inside the house to defrost themselves. Only a little heat is needed relative to heat capacity of a warm house. Mine does that. However, it still has resistive heating strips for emergency heating and for when the temperature falls too low for it to keep up.
nsxwolf 3y ago
Chicago, so those low temperatures are achievable.
- gooseyman 3y ago
  My understanding is that heat pumps operate at less than 100% efficiency at those levels. They don’t start blowing cold air, rather the air isn’t 90 degrees coming out any more.
- windexh8er 3y ago
  I have a 4 ton air source heat pump. It has both an internal heater and will run a defrost cycle by using the furnace in winter. I put in the full system a couple years ago. The entire system (100k BTU high efficiency furnace with variable output and 48k BTU, 22 SEER2 and 10.5 HSPF2) and the entire system was less than $17k. I also got over 4k in rebates (fed, state and manufacturer). I'm well north of Chicago. The heat pump is rated to -22F but have the lockout set to 15F to cut over to the furnace. Mostly for wear and tear reasons. But it has a COP rating of 1.75 at 5F. So still more efficient than any furnace well below where I run it.

Agreed. Ours is at least 5 years old if not more now and was way cheaper. That said there is a difference between mini-split and something you hook up to internal ducting where your furnace used to be and prices have increased in the meantime. That said there was basically no difference in putting in an A/C only unit vs a combination. Technology wise it's the same so to speak just running in reverse in winter vs summer. We use the heat pump down to -15C-ish then I usually shut it down and just use the baseboard or if awake the stove (looks much nicer ;)) It was a no brainer to get the combination unit really. I don't get why it isn't the default nowadays and A/C and heating are thought of as separate concerns. We just don't have ducting, else we could A/C the whole house vs. just one floor.

sokoloff 3y ago
Mechanically, there’s a reversing valve and defrost elements and controls to turn an AC into a heat pump. (So, it’s small, but not zero, mechanical differences.)
- tharkun__ 3y ago
  Thabks for the assist on the tech! And I can definitely attest to the heating element aka defrost. We don't have actual resistive heat in the pump as we have the baseboards anyway but the lower the outside temp goes the more it has to defrost the outside as it freezes up. As winter goes by, icicles form underneath the outside unit where the defrosted ice drains out and refreezes. It's actually amazing that the thing can extract heat from -10C air outside to heat up air that's already 21C inside to heat it up even further!
throw0101a 3y ago
> That said there is a difference between mini-split and something you hook up to internal ducting where your furnace used to be and prices have increased in the meantime. Generally true, as the mini-splits (have) tend(ed) to operate down to lower temperatures, but the heat pumps that look like 'traditional' outdoor A/C units are getting down there as well: for example this Lennox unit can work down to -4F / -20C: * https://tech.lennoxintl.com/c03e7o14l/viu12ch2uv/ehb_sl25xpv_2109.pdf https://tech.lennoxintl.com/c03e7o14l/viu12ch2uv/ehb_sl25xpv... That'll provide pretty good coverage of the year in many parts of North America before something like a gas furnace needs to kick in. (Speaking as someone who lives in Canada.)

rayiner 3y ago

They need them installed (and the extra dedicated 240v outlets, which can get expensive) for defrost cycles which happen below 35F or so.

xyzzyz 3y ago
Depends on whether they are reversible or not. Reversible ones, which can act as AC in summer, simply reverse themselves and act briefly as AC, essentially using heat taken from inside the house to defrost themselves. Only a little heat is needed relative to heat capacity of a warm house. Mine does that. However, it still has resistive heating strips for emergency heating and for when the temperature falls too low for it to keep up.

nsxwolf 3y ago

Chicago, so those low temperatures are achievable.

gooseyman 3y ago
My understanding is that heat pumps operate at less than 100% efficiency at those levels. They don’t start blowing cold air, rather the air isn’t 90 degrees coming out any more.
windexh8er 3y ago
I have a 4 ton air source heat pump. It has both an internal heater and will run a defrost cycle by using the furnace in winter. I put in the full system a couple years ago. The entire system (100k BTU high efficiency furnace with variable output and 48k BTU, 22 SEER2 and 10.5 HSPF2) and the entire system was less than $17k. I also got over 4k in rebates (fed, state and manufacturer). I'm well north of Chicago. The heat pump is rated to -22F but have the lockout set to 15F to cut over to the furnace. Mostly for wear and tear reasons. But it has a COP rating of 1.75 at 5F. So still more efficient than any furnace well below where I run it.