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Posted by on September 27, 2008, 4:46 am
Frigidaire sells a $29 5303918301 laminated "garage heater kit," with
2 wires that wraps around the cold control of a fridge to allow it to
work in to work in a cooler room, down to about 40 F.
It apparently heats the thermostat to fool the compressor into turning on,
even if the fridge compartment is cool enough (eg 40 F in a 40 F room.
Without this kit, the compressor does not run often enough to keep ice
cream from melting.
How does this work, exactly? Is the heater always on? Is it just adding
enough heat to the fridge compartment to make the compressor run long
enough to keep the freezer compartment frozen? If so, why is it
wrapped around the cold control, vs somewhere else in the fridge box?
I just bought an 18.2 CF Hotpoint fridge. I'd like to cover the outside
with 2" foamboard and run it in a cool kitchen to reduce the energy used
from 480 kWh/year to 240 or so, but Hotpoints don't come with these kits.
Would leaving the light on all the time in the fridge compartment do
the same thing? Is there a more energy-efficient way to do this? Warming
the whole fridge box takes more power than just warming the thermostat.
Nick
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Posted by Edwin Pawlowski on September 27, 2008, 7:38 am
> I just bought an 18.2 CF Hotpoint fridge. I'd like to cover the outside
> with 2" foamboard and run it in a cool kitchen to reduce the energy used
> from 480 kWh/year to 240 or so, but Hotpoints don't come with these kits.
> Would leaving the light on all the time in the fridge compartment do
> the same thing? Is there a more energy-efficient way to do this? Warming
> the whole fridge box takes more power than just warming the thermostat.
>
> Nick
>
Warming the fridge box is dumb too, as the food will be getting warm along
with the thermostat.
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Posted by on September 27, 2008, 11:14 am
>
>
>> I just bought an 18.2 CF Hotpoint fridge. I'd like to cover the outside
>> with 2" foamboard and run it in a cool kitchen to reduce the energy used
>> from 480 kWh/year to 240 or so, but Hotpoints don't come with these kits.
>> Would leaving the light on all the time in the fridge compartment do
>> the same thing? Is there a more energy-efficient way to do this? Warming
>> the whole fridge box takes more power than just warming the thermostat.
>
>Warming the fridge box is dumb too, as the food will be getting warm along
>with the thermostat.
The thermostat would still control the fridge temp. The Hotpoint manual says
don't run it in a room cooler than 60 F... 2" of extra foamboard would lower
the fridge box conductance to about 2 Btu/h-F and the freezer conductance to
about 1, so the freezer would need about 40 Btu/h of cooling at 0 F in a 40 F
room, which might come from a 15 watt bulb in a 40 F fridge box that runs
whenever the room is less than 60 F.
If the light uses 15 watts and the fridge uses 5, on average, that's 20x24h
= 480 Wh/day, ie 175 kWh/year if the room were always 40 F or 26x24h = 624
Wh/day if the room were always 70 F. It would be nice to get this down to
100 Wh, like the Mt. Best chest freezer fridge modification.
With better controls, it might only need 5x23h = 120 Wh/day.
Nick
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Posted by Edwin Pawlowski on September 27, 2008, 11:44 am
>
> If the light uses 15 watts and the fridge uses 5, on average, that's
> 20x24h
> = 480 Wh/day, ie 175 kWh/year if the room were always 40 F or 26x24h = 624
> Wh/day if the room were always 70 F. It would be nice to get this down to
> 100 Wh, like the Mt. Best chest freezer fridge modification.
>
> With better controls, it might only need 5x23h = 120 Wh/day.
>
> Nick
>
The thermostat unit heats just that tiny portion of the unit to make the
freezer be colder. To warm the entire refrigerator box with a 40W bulb is
wasteful and will warm the contents a bit. Saving energy at the expense of
potential food deterioration or spoilage does not make sense.
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Posted by on September 27, 2008, 4:32 pm
>
>>
>> If the light uses 15 watts and the fridge uses 5, on average, that's
>> 20x24h = 480 Wh/day, ie 175 kWh/year if the room were always 40 F or
>> 26x24h = 624 Wh/day if the room were always 70 F. It would be nice
>> to get this down to 100 Wh, like the Mt. Best chest freezer fridge
>> modification.
>>
>> With better controls, it might only need 5x23h = 120 Wh/day.
Or 24h(40F-10F)1Btu/h-F/3.41Btu/h/W/3COP = 70 Wh/day, ie 26 kWh/year
worth $2.60 per year at 10 cents/kWh, with a 10 F freezer compartment
and a 40 F fridge compartment in a 40 F room.
>The thermostat unit heats just that tiny portion of the unit to make the
>freezer be colder.
But the thermostat's in the fridge compartment, no? The fridge wants to
be about 34 F...
>To warm the entire refrigerator box with a 40W bulb is wasteful and will
>warm the contents a bit.
Who mentioned 40 watts? A bulb in the box would not change the box temp.
Nick
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