3 ms·

How do freezers work if heat pumps stop working at 32F?

by lasson 5y ago

throwaway0a5e 5y ago
Freezers use a different refrigerant that gives them a different working temperature range. Additionally, for proper efficiency the key components of the system need to be sized for your target temperature and the temperature range of your ambient air.
jqpabc123 5y ago
With heat pump systems, "inside" is the temperature being controlled. "Outside" is uncontrolled --- it's where heat is being dumped to or pulled from. Don't confuse the two. The efficiency of a home heat pump declines as the air temperature outside the home drops. A freezer is working in reverse so it's efficiency declines as the air temperature outside the freezer box rises. Neither a heat pump in an Alaskan winter nor a freezer sitting on a Florida back porch in summer are operating very efficiently.
- MauranKilom 5y ago
  I believe the point was that both a pump for heating in winter as well as a fridge/freezer try to move energy from the colder to the warmer side. Seeing as freezers can successfully extract energy from the side that is below freezing, it stands to reason that the same should be possible for a "keep your home warm, even in winter" heat pump. Now, the original claim of "heat pumps don't work below freezing" is trivially wrong (and so the question by lasson was justified), but the overall point is that heat pump efficiency gets worse the more you need it in the case of keeping your home warm.
  - jqpabc123 5y ago
    Seeing as freezers can successfully extract energy from the side that is below freezing... Invalid assumption. Whether it can or not depends on the environment. Most ordinary freezers are designed to operate within a relatively luxurious temperature controlled in-door environment. Stick one in the sun on a Florida back porch in August and you may well discover it can no longer successfully "extract energy from the side that is below freezing". Same thing (only in reverse) can happen with a home heat pump in an Alaskan winter. There is another important element here --- energy loss and insulation. At a certain temperature (whatever it may be), the energy lost to the surroundings will start to exceed the capacity of the heat pump. At some point; speaking in practical terms, the heat pump becomes essentially worthless. You need either a bigger heat pump or you need more insulation to stop the loss --- both of which cost money and can't be obtained/installed immediately.
    - Siecje 5y ago
      When the heat pump can't keep up you use resistance heating in the air handler. Since this only runs for a short period of time it doesn't make a big difference in cost.
    - deleted 5y ago
      [deleted]

How do freezers work if heat pumps stop working at 32F?

by lasson 5y ago

How do freezers work if heat pumps stop working at 32F?

Freezers use a different refrigerant that gives them a different working temperature range. Additionally, for proper efficiency the key components of the system need to be sized for your target temperature and the temperature range of your ambient air.

jqpabc123 5y ago

With heat pump systems, "inside" is the temperature being controlled. "Outside" is uncontrolled --- it's where heat is being dumped to or pulled from. Don't confuse the two. The efficiency of a home heat pump declines as the air temperature outside the home drops. A freezer is working in reverse so it's efficiency declines as the air temperature outside the freezer box rises. Neither a heat pump in an Alaskan winter nor a freezer sitting on a Florida back porch in summer are operating very efficiently.

MauranKilom 5y ago
I believe the point was that both a pump for heating in winter as well as a fridge/freezer try to move energy from the colder to the warmer side. Seeing as freezers can successfully extract energy from the side that is below freezing, it stands to reason that the same should be possible for a "keep your home warm, even in winter" heat pump. Now, the original claim of "heat pumps don't work below freezing" is trivially wrong (and so the question by lasson was justified), but the overall point is that heat pump efficiency gets worse the more you need it in the case of keeping your home warm.
- jqpabc123 5y ago
  Seeing as freezers can successfully extract energy from the side that is below freezing... Invalid assumption. Whether it can or not depends on the environment. Most ordinary freezers are designed to operate within a relatively luxurious temperature controlled in-door environment. Stick one in the sun on a Florida back porch in August and you may well discover it can no longer successfully "extract energy from the side that is below freezing". Same thing (only in reverse) can happen with a home heat pump in an Alaskan winter. There is another important element here --- energy loss and insulation. At a certain temperature (whatever it may be), the energy lost to the surroundings will start to exceed the capacity of the heat pump. At some point; speaking in practical terms, the heat pump becomes essentially worthless. You need either a bigger heat pump or you need more insulation to stop the loss --- both of which cost money and can't be obtained/installed immediately.
  - Siecje 5y ago
    When the heat pump can't keep up you use resistance heating in the air handler. Since this only runs for a short period of time it doesn't make a big difference in cost.
  - deleted 5y ago
    [deleted]