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I just bought a Mitsubishi mini split system to replace our oil furnace and bring A/C to our house here in New Jersey for the first time. Their high end outdoor

by Jgrubb 4y ago

I just bought a Mitsubishi mini split system to replace our oil furnace and bring A/C to our house here in New Jersey for the first time. Their high end outdoor units heat down to -13 F, which is colder than I've ever seen here. It arrives in august. Gree has a system that claims to have full heat down to -31, so I'd say just keep researching and you'll probably be fine.

throw0101a 4y ago
> Gree has a system that claims to have full heat down to -31, so I'd say just keep researching and you'll probably be fine. Doing a quick search, they're using 'standard' R410A refrigerant (PDF): * https://www.greecomfort.com/assets/our-products/multi-plus-ultra/documents/multi-plus-ultra-service-parts-catalog-d.pdf https://www.greecomfort.com/assets/our-products/multi-plus-u... the same as everyone else. It seems just that they though it worth the engineering effort to push a little further than most other companies. See anything with the label "For Extreme Conditions": * https://www.greecomfort.com/our-products/ https://www.greecomfort.com/our-products/
david422 4y ago
What is the plan for when it gets colder than -13? Do you do a hybrid with your furnace? Some other solution? Thinking of getting some heat pumps myself.
- leviathant 4y ago
  In nearby Philadelphia, it rarely gets that cold, and not for extended periods of time, but when it does, we bust out blankets and space heaters to make up the difference.
- sokoloff 4y ago
  I’ve looked into heat pumps pretty extensively for my upcoming boiler replacement (looking at an air-to-water in my case, but very similar principles apply). In my case, the 99% design temperature is high single digits Fahrenheit. For the 3.5 days/year colder than that, the plan is to have the house “coast” on thermal mass. That’s for cases where the ambient temp is below design (where the heater can make heat but just no longer enough to keep up with the building heat loss), not for when it’s below a cutoff (where the heater shuts off entirely). In my case, that’s so far below design temp that I’d expect to never see it. (We hit -9°F in 2016 and would have to go all the way back to 1943 to find a low of -14°F.) If it happened, thermal mass would start to carry us with electric space heating keeping the house from totally freezing.
  - hamandcheese 4y ago
    I might invest in some backup propane heaters as well (a buddy heater at Walmart is pretty affordable and is safe for indoor use). I feel like in blizzard-like conditions having electricity be your backup plan might not be too wise.
- Jgrubb 4y ago
  We usually switch to the wood stoves once winter sets in. Our forced air furnace is incapable of making the house warm and cozy because duct reasons that I can't really fix. I'm planning on getting rid of it altogether and doing the heat pump(s) most of the year, the wood stoves in winter and reclaiming a lot of headroom in the basement and an entire utility room that the furnace currently takes up.
- 0x53 4y ago
  They way it works in practice is that the air handler that comes with the heat pump will contain a backup emergency heat element in case it gets too cold or there is a problem with the heat pump. The cost to run it is much higher, but it should only run in the most extreme cold temperatures.

by Jgrubb 4y ago

throw0101a 4y ago

> Gree has a system that claims to have full heat down to -31, so I'd say just keep researching and you'll probably be fine. Doing a quick search, they're using 'standard' R410A refrigerant (PDF): * https://www.greecomfort.com/assets/our-products/multi-plus-ultra/documents/multi-plus-ultra-service-parts-catalog-d.pdf https://www.greecomfort.com/assets/our-products/multi-plus-u... the same as everyone else. It seems just that they though it worth the engineering effort to push a little further than most other companies. See anything with the label "For Extreme Conditions": * https://www.greecomfort.com/our-products/ https://www.greecomfort.com/our-products/

david422 4y ago

What is the plan for when it gets colder than -13? Do you do a hybrid with your furnace? Some other solution? Thinking of getting some heat pumps myself.

leviathant 4y ago
In nearby Philadelphia, it rarely gets that cold, and not for extended periods of time, but when it does, we bust out blankets and space heaters to make up the difference.
sokoloff 4y ago
I’ve looked into heat pumps pretty extensively for my upcoming boiler replacement (looking at an air-to-water in my case, but very similar principles apply). In my case, the 99% design temperature is high single digits Fahrenheit. For the 3.5 days/year colder than that, the plan is to have the house “coast” on thermal mass. That’s for cases where the ambient temp is below design (where the heater can make heat but just no longer enough to keep up with the building heat loss), not for when it’s below a cutoff (where the heater shuts off entirely). In my case, that’s so far below design temp that I’d expect to never see it. (We hit -9°F in 2016 and would have to go all the way back to 1943 to find a low of -14°F.) If it happened, thermal mass would start to carry us with electric space heating keeping the house from totally freezing.
- hamandcheese 4y ago
  I might invest in some backup propane heaters as well (a buddy heater at Walmart is pretty affordable and is safe for indoor use). I feel like in blizzard-like conditions having electricity be your backup plan might not be too wise.
Jgrubb 4y ago
We usually switch to the wood stoves once winter sets in. Our forced air furnace is incapable of making the house warm and cozy because duct reasons that I can't really fix. I'm planning on getting rid of it altogether and doing the heat pump(s) most of the year, the wood stoves in winter and reclaiming a lot of headroom in the basement and an entire utility room that the furnace currently takes up.
0x53 4y ago
They way it works in practice is that the air handler that comes with the heat pump will contain a backup emergency heat element in case it gets too cold or there is a problem with the heat pump. The cost to run it is much higher, but it should only run in the most extreme cold temperatures.