Garage heater kit for fridge?
nicks...@ece.villanova.edu
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
Edwin Pawlowski
<nicks...@ece.villanova.edu> wrote in message
> 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.
Uncle Monster
was a crankcase heater for the compressor but something I
read indicates that the heater is for adding heat to the
"control compartment" to fool the thermostat into making
the compressor run for a longer period of time. It also
negates the Energy Star rating of the fridge. I do a lot
of commercial refrigeration where pressure controls may
be used in lieu of thermostats ie, better temperature
control over a wider ambient but much more expensive. I
could adapt a home refrigerator to run well in low ambient
conditions by adding extra controls and sensors but the
control compartment heater is simple and cheap. KISS
[8~{} Uncle Monster
nicks...@ece.villanova.edu
>
><nicks...@ece.villanova.edu> wrote in message
>
>> 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.
>
>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
ransley
I would not jump into this without research, my home ac condensor has
a heater for the compressor , there are low temp ratings for all
compressor equipment I have. My low temp warning is about 50-55f for
my sears energy star frige. I would worry about ruining the unit,
leaving a light on will just waste energy like opening the door 24hrs
a day.
nicks...@ece.villanova.edu
>... something I read indicates that the heater is for adding heat to the
>"control compartment" to fool the thermostat into making the compressor
>run for a longer period of time.
Is the heater always on? Maybe it turns off when the compressor runs?
Why heat the control compartment instead of the box?
If the control is heated, the thermostat could still work, but the fridge box
would be colder than without the heater, given the same thermostat setting.
Putting a bulb in the box would just increase the run time without affecting
the box temp.
This could be more efficient with 2 fans and 2 thermostats and no heater.
Disabling the door heater and auto-defrost could also help.
Nick
Edwin Pawlowski
<nicks...@ece.villanova.edu> wrote in message
>
> 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.
AZ Nomad
>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.
If your fridge/freezer is such a POS that it is too stupid to run the
compressor when the freezer is too warm, then you ought to either replace
it or get a separate freezer.
Uncle Monster
heater puts out very little heat.
The heat is just enough to trick
the thermostat, not to warm the
refrigerator compartment. Home
refrigerators are designed to
operate within the typical ambient
temperatures found in a living
space. The much more expensive
commercial refrigeration systems
are designed to operate in places
that would be quite uncomfortable
for me and thee. It's all about
cost and affordability. What I've
seen of Sub-Zero refrigerators, a
line of very expensive refrigerators,
looks like commercial equipment to
me, I couldn't afford one.
[8~{} Uncle Monster
nicks...@ece.villanova.edu
>
><nicks...@ece.villanova.edu> wrote in message
>>
>> 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
nicks...@ece.villanova.edu
>... The heat is just enough to trick the thermostat, not to warm the
>refrigerator compartment.
How would that accomplish the goal?
Nick
Edwin Pawlowski
<nicks...@ece.villanova.edu> wrote in message
>>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
>
If it does not change the box temperature, it is not going to make the
thermostat do its thing. 40 watts burning adds heat and while it is mostly
overcome by the operation of the compressor, it still has to raise the
temperature a bit. How much depends on the differential of the thermostat.
Wayne Boatwright
> 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.
Maybe you should have bought the Frigidaire. Problem solved.
> 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.
How cold do you plan on keeping the kitchen? Most refrigerators perform
perfectly well down to around 60°F. Unless you're always dressed for
winter, anything lower could hardly be considered comfortable. I must
say, a refrigerator encased in 2" foamboard sounds really "attractive".
Not! Why on earth would you really want to do this? I don't think you'll
be saving a thing and you need a different project. :-)
--
Wayne Boatwright
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Date: Saturday, 09(IX)/27(XXVII)/08(MMVIII)
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Uncle Monster
pictures of your particular fridge
but I'm guessing that there is a
housing in the top of the refrigerator
compartment that contains a thermostat,
defrost timer and perhaps light bulb.
The housing has openings that allow
the air to circulate around the thermostat.
The slight heat produced by the heater
is enough to raise the temperature around
the thermostat to trick it into running
the compressor for a longer period of time.
It's not necessary to increase the temperature
of the whole refrigerated box, just the
temperature around the thermostat.
[8~{} Uncle Monster
nicks...@ece.villanova.edu
><nicks...@ece.villanova.edu> wrote in message
>>>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.
>
>If it does not change the box temperature, it is not going to make the
>thermostat do its thing.
The box temp change would be minimal.
>... 40 watts burning adds heat
Who mentioned 40 watts?
Nick
nicks...@ece.villanova.edu
>How cold do you plan on keeping the kitchen?
I kept it 36 F one year.
Nick
nicks...@ece.villanova.edu
>>> ... The heat is just enough to trick the thermostat, not to warm the
>>> refrigerator compartment.
>>
>> How would that accomplish the goal?
>The slight heat produced by the heater is enough to raise the temperature
>around the thermostat to trick it into running the compressor for a longer
>period of time. It's not necessary to increase the temperature of the whole
>refrigerated box, just the temperature around the thermostat.
That doesn't make sense to me...
Nick
Wayne Boatwright
That's beyond my comprehension.
At that temperature, you don't even need a refrigerator, just a freezer.
--
Wayne Boatwright
*******************************************
Date: Saturday, 09(IX)/27(XXVII)/08(MMVIII)
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Edwin Pawlowski
<nicks...@ece.villanova.edu> wrote in message
>
> Who mentioned 40 watts?
>
> Nick
>
Typical appliance bulb wattage
larry
It's like the timer with a 10K resistor clipped under a
regular wall thermostat to do an over-night "setback".
Thermostat thinks it's getting warmer and turns off the
furnace when the room isn't warmer.
Frig controls are wacky these days, you chill the freezer,
themostat the coldbox, and use a fan and vent to regulate
the freezer temp.
If the differential is that small, why not use a few "frig"
chips (Peltier devices) to do the job in place of the
compressor? A single one sq inch chip will cool your six
pack in your 12v car cooler in the summer. Or an old Bernz
with the Ammonia absorption cooler. I have a 1950's
12v/110v portable that will still develop a 60 degree
differential and bust 2 six packs of soda in the basement
during the winter ;-)
-- larry / dallas
nicks...@ece.villanova.edu
>nicks...@ece.villanova.edu wrote:
>> Uncle Monster <uncle-...@dillywacker.net> wrote:
>>
>>>>> ... The heat is just enough to trick the thermostat, not to warm the
>>>>> refrigerator compartment.
>>>> How would that accomplish the goal?
>>
>>> The slight heat produced by the heater is enough to raise the temperature
>>> around the thermostat to trick it into running the compressor for a longer
>>> period of time. It's not necessary to increase the temperature of the whole
>>> refrigerated box, just the temperature around the thermostat.
>>
>> That doesn't make sense to me...
>
>regular wall thermostat to do an over-night "setback".
>Thermostat thinks it's getting warmer and turns off the
>furnace when the room isn't warmer.
But that makes the room colder at night. How do we keep the fridge
a constant 40 F and the freezer frozen in a 40 F room?
If the freezer stays 0 F in a 60 F room while the 40 F fridge box
is gaining Q Btu/h from the room, cooling the room to 50 will reduce
the fridge gain to Q/2, so the compressor will run half the time.
But the required freezer run time will only go down by 50/60, so
we need to add enough heat to the fridge box (vs the thermostat box)
to raise the run time back up to 50/60 of the 60 F room run time, no?
The fridge box won't absorb any heat at all from a 40 F room, but
the freezer still needs 40/60 of the 60 F room run time to stay 0 F.
Nick
nicks...@ece.villanova.edu
>>>How cold do you plan on keeping the kitchen?
>>
>> I kept it 36 F one year.
>
>That's beyond my comprehension.
It's easy to do with the kitchen off the back of my house. With 2' stone
walls (C ~ 50 Btu/F-ft^2) inside R10 insulation and RC = 500 hours,
the kitchen temp changes slowly.
Starting at 36 F, it would cool to 30+(36-30)e^-(24h/500h) = 35.7 over
an average 30 F January day. Leaving the kitchen door to the rest of
the house open for a few minutes a day makes up for that cooling.
>At that temperature, you don't even need a refrigerator, just a freezer.
Right, but then spring happens. Maybe the freezer needs a thermostat
that turns on a 15 watt bulb in the fridge box when the freezer temp
rises to 10 F. Where can I find one of those?
Nick
Nick Pine
>in the fridge box when the freezer temp rises to 15 F. Where can I find
>one of those?
Aha. Danfoss 015-0283, for $23.95...
http://www.rparts.com/Catalog/Major_Components/controls/015-0283r.htm
Nick
larry
The way the closed loop control works on modern frig's is
working against you. You need a little redesign.
Given:
1. the freezer, goal=0F, always needs cool in your ambient
temp range, 40F to 80?F.
2. the coldbox (frig - i hate these terms), goal=36F, needs
cool on hot days and maybe none on cold days.
Plan:
1. freezer, meet the demand first, put the thermostat for
the freezer IN THE FREEZER, where the coils are to begin
with. Closed the loop on the freezer, it will take care of
itself.
2. Coldbox. Block the existing air path between the freezer
and the coldbox below. Control that airflow with a moving
vane and and fan connected to a thermostat in the coldbox to
cool the coldbox with cold air from the freezer to the
target temp 40F.
Cheap way of doing the coldbox control is a bimetalic strip
in the coldbox that pushes the vane open as the temperature
exceeds 40F. A small microswitch could switch on the fan as
long as it detects the vane is open.
Just about everything you need is already in the frig. Take
up the baseplate in the freezer, you will see the cooling
coils, the air path, with vane, to the coldbox, and a fan
near the back, that circulates cool in the freezer and
coldbox. Plus a big heater to thaw the coils. There is a
schematic in an envelop near the compressor or defrost tray.
I don't know how this will affect defrost cycle.
second thought, close off the kitchen and roll the frig to
the living room... You can't be married... ;-)
-- larry/dallas
btw, the resistor/timer will work if you invert the
function, resistor on for less heating, resistor off for
less cooling.
Uncle Monster
systems I install/build/repair usually work well
regardless of the ambient temperature. I'm about
to move two walk in coolers and reinstall them
where the condensing units will be in a back room
rather than two stories up on a roof. The units
will work without a problem because of their more
sophisticated control system than a home refrigerator.
The control systems use not only thermostats but
pressure and fan controls to maintain the temperature.
I've worked on Sub-Zero brand refrigerators made
for home use that were built like commercial coolers
with semi-hermetic compressors and commercial controls
but GOLLY! those damn things are expensive. They will
work in just about any ambient temperature but the
cost is out of my range. I could always take a standard
home refrigerator and modify it for a lot less money.
[8~{} Uncle Monster
Wayne Boatwright
> Wayne Boatwright <waynebo...@gmail.com> wrote:
>
>>>>How cold do you plan on keeping the kitchen?
>>>
>>> I kept it 36 F one year.
>>
>>That's beyond my comprehension.
>
> It's easy to do with the kitchen off the back of my house. With 2' stone
> walls (C ~ 50 Btu/F-ft^2) inside R10 insulation and RC = 500 hours,
> the kitchen temp changes slowly.
>
> Starting at 36 F, it would cool to 30+(36-30)e^-(24h/500h) = 35.7 over
> an average 30 F January day. Leaving the kitchen door to the rest of
> the house open for a few minutes a day makes up for that cooling.
Being able to do it is not beyond my comprehension. Why anyone would
really want to do it is beyond my comprehension. I want every room in my
house to be at a comfortable temperature at all times. I would find it
inconvenient and uncomfortable to have to wait for it to warm up enough for
the kitchen to be useful.
You are not saving siginficant energy, since to be able to use the kitchen
you're robbing other parts of the house of its heat which has to be
compensated for each time you do it.
>>At that temperature, you don't even need a refrigerator, just a freezer.
>
> Right, but then spring happens. Maybe the freezer needs a thermostat
> that turns on a 15 watt bulb in the fridge box when the freezer temp
> rises to 10 F. Where can I find one of those?
Well, yes, spring happens. As to where to find what you're looking for, I
have no idea.
--
Wayne Boatwright
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Date: Monday, 09(IX)/29(XXIX)/08(MMVIII)
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Larry W
<nicks...@ece.villanova.edu> wrote:
>Uncle Monster <uncle-...@dillywacker.net> wrote:
>
>>>> ... The heat is just enough to trick the thermostat, not to warm the
>>>> refrigerator compartment.
>>>
>>> How would that accomplish the goal?
>
>That doesn't make sense to me...
>
>Nick
>
The darn thing works, does it need to make any more sense than that?
--
Better to be stuck up in a tree than tied to one.
Larry Wasserman - Baltimore Maryland - lwasserm(a)sdf. lonestar.org
nicks...@ece.villanova.edu
>>>>>How cold do you plan on keeping the kitchen?
>>>>
>>>> I kept it 36 F one year.
>>>
>>>That's beyond my comprehension.
>>
>> It's easy to do with the kitchen off the back of my house. With 2' stone
>> walls (C ~ 50 Btu/F-ft^2) inside R10 insulation and RC = 500 hours,
>> the kitchen temp changes slowly.
>>
>> Starting at 36 F, it would cool to 30+(36-30)e^-(24h/500h) = 35.7 over
>> an average 30 F January day. Leaving the kitchen door to the rest of
>> the house open for a few minutes a day makes up for that cooling.
With the door to the rest of the house closed, it would cool from 36 to 32
in -500ln((32-30)/(36-30)) = 549 hours, ie 23 days.
>Being able to do it is not beyond my comprehension. Why anyone would
>really want to do it is beyond my comprehension.
Pity.
>You are not saving siginficant energy, since to be able to use the kitchen
>you're robbing other parts of the house of its heat which has to be
>compensated for each time you do it.
Au contraire, the fridge uses less energy in a cool room, and the room
itself needs less heat if it's cooler on average.
>As to where to find what you're looking for, I have no idea.
Danfoss sells $24 freezer stats...
Nick
Wayne Boatwright
> Wayne Boatwright <waynebo...@gmail.com> wrote:
>
>>>>>>How cold do you plan on keeping the kitchen?
>>>>>
>>>>> I kept it 36 F one year.
>>>>
>>>>That's beyond my comprehension.
>>>
>>> It's easy to do with the kitchen off the back of my house. With 2'
>>> stone walls (C ~ 50 Btu/F-ft^2) inside R10 insulation and RC = 500
>>> hours, the kitchen temp changes slowly.
>>>
>>> Starting at 36 F, it would cool to 30+(36-30)e^-(24h/500h) = 35.7 over
>>> an average 30 F January day. Leaving the kitchen door to the rest of
>>> the house open for a few minutes a day makes up for that cooling.
>
> With the door to the rest of the house closed, it would cool from 36 to
> 32 in -500ln((32-30)/(36-30)) = 549 hours, ie 23 days.
>
>>Being able to do it is not beyond my comprehension. Why anyone would
>>really want to do it is beyond my comprehension.
>
> Pity.
I can't imagine anyone else in the civilized world wanting to do this.
Most would probably find this a very uncomfortable situation at best.
>>You are not saving siginficant energy, since to be able to use the
>>kitchen you're robbing other parts of the house of its heat which has to
>>be compensated for each time you do it.
>
> Au contraire, the fridge uses less energy in a cool room, and the room
> itself needs less heat if it's cooler on average.
Are you doing this to save money or as just a weird experiment?
>>As to where to find what you're looking for, I have no idea.
>
> Danfoss sells $24 freezer stats...
Then you've found your answer.
--
Wayne Boatwright
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