3 ms·

Is there such a thing as too cold for heat pumps though? They drop in efficiency, sure, but still beat resistive heating. Modern ones are still going to be 300%

by brnt 5y ago

Is there such a thing as too cold for heat pumps though? They drop in efficiency, sure, but still beat resistive heating. Modern ones are still going to be 300% efficient down to -20C or so. With a resistive pre heater I don't see how they'll ever not be more efficient than resistive heating.

BizarroLand 5y ago
My heat pump is a Trane heat pump from 2018 and it goes into emergency heat mode when the temps are below 36, which is off and on for most of the winter. I wonder if I should have it serviced to make sure it's working correctly.
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- bcrosby95 5y ago
  It's partially a function of your heating demands. My sister's emergency heat mode would run all the time in her town house. But she installed a giant insulating curtain over one of her leaky sliders and now it almost never needs to run.
  - BizarroLand 5y ago
    That seems more like she improved her insulation, decreasing her heating needs rather than addressing the temperature cutoff for a heat pump. I still like the heat pump because in the summer my power bill for cooling a 2600 sq ft home is about $50/month, and in the winter I do have a wood burning stove that I can run to heat the house when the temps are below 36. That and recirc mode on the fan unit can keep my power bills to a minimum.
nybble41 5y ago
A heat pump with a sufficiently powerful resistive preheater will be at least as energy-efficient in operation as the resistive heater alone, but it's also much more complex, with a correspondingly higher up-front cost and ongoing maintenance requirements. A resistive heater can consist of little more than a solid-state heating element, a blower fan, and a mechanical thermostat; radiative heaters can even dispense with the fan, which is the least reliable part of the system. A heat pump, by contrast, additionally involves pumps, heat exchangers, and volatile fluids under pressure, generally under the management of some moderately complex logic.
- brnt 5y ago
  Naturally a heat pump is more complex and thus more maintenance intensive, but it's worth the investment/cost in energy savings in any calculation I've seen (they do tend to require more maintenance).
  - nybble41 5y ago
    Cost is one factor, but if you live in, say, rural North Dakota, you may not be able to afford the risk that your main source of heat breaks down in the middle of a blizzard and you can't get anyone in to service it for several days… or weeks. Don't discount the value of predictable reliability.

by brnt 5y ago

BizarroLand 5y ago

My heat pump is a Trane heat pump from 2018 and it goes into emergency heat mode when the temps are below 36, which is off and on for most of the winter. I wonder if I should have it serviced to make sure it's working correctly.

deleted 5y ago
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bcrosby95 5y ago
It's partially a function of your heating demands. My sister's emergency heat mode would run all the time in her town house. But she installed a giant insulating curtain over one of her leaky sliders and now it almost never needs to run.
- BizarroLand 5y ago
  That seems more like she improved her insulation, decreasing her heating needs rather than addressing the temperature cutoff for a heat pump. I still like the heat pump because in the summer my power bill for cooling a 2600 sq ft home is about $50/month, and in the winter I do have a wood burning stove that I can run to heat the house when the temps are below 36. That and recirc mode on the fan unit can keep my power bills to a minimum.

nybble41 5y ago

A heat pump with a sufficiently powerful resistive preheater will be at least as energy-efficient in operation as the resistive heater alone, but it's also much more complex, with a correspondingly higher up-front cost and ongoing maintenance requirements. A resistive heater can consist of little more than a solid-state heating element, a blower fan, and a mechanical thermostat; radiative heaters can even dispense with the fan, which is the least reliable part of the system. A heat pump, by contrast, additionally involves pumps, heat exchangers, and volatile fluids under pressure, generally under the management of some moderately complex logic.

brnt 5y ago
Naturally a heat pump is more complex and thus more maintenance intensive, but it's worth the investment/cost in energy savings in any calculation I've seen (they do tend to require more maintenance).
- nybble41 5y ago
  Cost is one factor, but if you live in, say, rural North Dakota, you may not be able to afford the risk that your main source of heat breaks down in the middle of a blizzard and you can't get anyone in to service it for several days… or weeks. Don't discount the value of predictable reliability.