Freezer in freezing conditions [RE-wrenches]
Jeffrey Wolfe, Global Resources
global at sover.net
Mon Aug 21 13:02:37 EDT 2000
Here's the technical scoop. (Maybe more than you wanted to know?)
The freezer (or refrigerator) works in the following stages:
1. Compress the refrigerant gas to high pressure. Also results in high
temp.
2. Cool the "hot gas" in the condensor. (The condensor is the coils outside
the box.) The objective is to create a liquid, a little below its boiling
point (at the working pressure). How far below boiling it is depends upon
the exact design, but typically no more than about 15 degrees F.
3. The "liquid" is then put through an expansion device. On a residential
fridge or freezer, this is usually a static device, just an orifice. So it
does not adjust for load or varying inlet conditions of the liquid. The
expansion device makes a gas from the liquid. When it expands, it drops in
temperature. (This is how we can cool the gas with a condenser at 100
degrees F and then cool the food at 0 deg F.)
4. After the expansion device, we have "cold gas". This cold gas goes into
the evaporator, which is the plate inside the fridge or freezer that cools
it. In the evaporator, the cold gas must ALL warm up, so that it is hot
enough so that there is NO liquid when it gets to the compressor.
5. Now the "warm gas" after the evaporator goes back to the compressor.
So where the problem comes in is if the evaporator does not add enough heat
into the refrigerant gas to get it warm enough. This is compounded when the
liquid gets too cold in the condensor, since it may not all vaporize when
it goes through the (static) expansion device. The result is called "liquid
slugging" the compressor. It can ruin it very quickly, kind of like putting
sand through it.
The reason it does not happen too often can vary, such as the garage is not
really that cold, or the unit actually does not run at all when it gets to
the point that it might get damaged, etc. But it can happen that you can
destroy a unit. It can also happen that it uses a lot more energy, since
trying to compress liquid is basically impossible.
I don't know of any sure-fire recommendations to avoid problems. I know
that the folks at GE, etc., are not thinking "energy conservation, let's
make this thing so it can operate in cold weather" when they design their
units. I typically do NOT recommend to clients that they put them outside.
Sometimes they do, but I don't want to buy any new compressors.
Jeff
Jeffery D. Wolfe, P.E.
Global Resource Options, LLP
A Woman-Owned Limited Liability Partnership
4 Kibling Hill Road
P.O. Box 51
Strafford, VT 05072
800-374-4494 Toll Free
802-765-4632 Phone
802-765-9983 Fax
global at sover.net
www.globalresourceoptions.com
----------
From: Bob Ellison, Alternative Energy Systems[SMTP:ellison at gisco.net]
Reply To: RE-wrenches at topica.com
Sent: Monday, August 21, 2000 9:33 AM
To: RE-wrenches at topica.com
Subject: RE: Freezer in freezing conditions [RE-wrenches]
Jim is correct, but those are commercial compressors and they sometimes
have
heaters to keep the oil in the base warm to ease starting in cold weather.
Similar to a car having a block heater to keep the engine warm. They also
are remote compressor units with the compressor located outside and the
refrigerated area in a building. In a case like that the compressor would
have to start in all weather to provide cooling.
In the case of a freezer in a garage it would not even come on because
there
is no need for further cooling when the temperature is already low. An
outside refrigerator or freezer will pretty much protect themselves in this
case.
Bob Ellison
-----Original Message-----
From: James Lamb, Middle Fork Engineering [mailto:j.lamb at pecorp.com]
Sent: Monday, August 21, 2000 8:56 AM
To: RE-wrenches at topica.com
Subject: RE: Freezer in freezing conditions [RE-wrenches]
If you start a refrigerator or freezer in a cold environment. It can blow
the compresser. It has somthing to do with the refrigerant or being in a
liqiud state in a cold environment and the compressor not being able to
compress the liquid. This can break the refrigerant valve on top of the
compressor. Long ago when electric refrigerators became available a
compressor heater was installed because people were putting their
refrigerators in cold porches and breaking the compressor. The best way to
do this is to put the box in a cold environment and keep the compressor in
a
warm place. I do not know it you can put the condenser coil in a cold
environment. There is a limit 40 - 50 degrees. It probably depends on the
unit itself Any other thoughts on this
Jim Lamb
Middle fork engineering
> ----------
> From: Chuck Heath, SunPower[SMTP:sunpwr at jps.net]
> Reply To: RE-wrenches at topica.com
> Sent: Monday, August 21, 2000 7:34 AM
> To: RE-wrenches at topica.com
> Subject: Freezer in freezing conditions [RE-wrenches]
>
> A computer friend asks this question, to which I have no answers:
>
> We are moving and wish to' temporarily' store a working chest freezer in
> an unheated garage. I have a residual thought somewhere that it might not
> work in a cold New England winter environment - something about heat
> exchange. Any ideas are appreciated.
>
> Chuck Heath _who escaped from bitter cold winters years ago_
>
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