using a fridge in sub zero temps [Science]

2011 Dec 1
Anyone know how to make a fridge work properly if it's being used in a place that's below freezing?

I know that sounds like an appliance question, but being the two fridges in question store our farms milk and eggs, I say this is totally food related! ;-)

I'm under the impression that once the temp is below zero, the freezer compartments defrost system doesn't work right, so then the fridge compartment doesn't work right either.

Both fridges are outside in an insulated, but unheated building. Any ideas on how I can still use them? It's been pretty mild the last while, but it's bound to get cold at some point, right?

2011 Dec 1
A fridge doesn't have the capacity to keep it's inside warmer than the outside environment. There is only a cooling system, no heating system (except possibly the defrost system, but it's not meant for that purpose and only produces heat very intermitently).

So if the room is below freezing, everything in the fridge will eventually be at that temperature too. And the fridge is likely to stop working altogether. Really, checking the manual from the fridge might be a good idea. I doubt that it is recommanded to use it at a temperature even close to the freezing point.

The only way to keep using the fridge in a cold room I could think of would be to build a big insulated box around the fridge, so that the heat produced outside the fridge could keep the air around the fridge above freezing... but I don't think that would work when we hit 20 below.

2011 Dec 1
the fridge works by removing heat from inside and releasing it outside. since the temperature differential between the outside and inside will be negative, i.e. colder outside than in, there won't be any heat to remove from the inside, and it will reach the same temperature as outside. you'll need a heat source to keep the inside warmer than outside.

just think of your home... you have a furnace and an AC. the AC cannot warm up your house.

2011 Dec 1
Strange though it may sound, if you want to store things at fridge temperature (usually between 1.5 and 3 celsius) in an environment where the ambient temperature is below freezing, you might be better off putting a thermostatically controlled heating mat such as is used in beer making in the bottom of a fridge that is turned off. The fridge would provide the insulation, and the heating mat would keep the temperature at a level to stop the milk and eggs from freezing.

2011 Dec 1
You can actually do this by jigging with the circuitry and installing a Johnson A419 controller to jack into the compressor circuit at the right location as well as the light bulb circuit. The light should be enough to keep the fridge warm in sub zero, but I'd test it thoroughly before trusting food to it.

I know a local pig farmer who could probably do it ;-) He's also an engineer

EDIT: actually I know a few people who might do it for some free pork - but you'd have to buy the A419s

2011 Dec 3
You could get one of these on eBay. It will control two devices, the cooling device and the heating device.

The most trouble free way to do it would be to wire it into the fridge thermostat control for cooling, and maybe a ceramic heater bulb for reptile cages.

I have a couple of these, new in box, spare actually. I bought them to play around with sous vide. I don't eat meat. But I'm an Engineer. I would do it for you at a convenient time.

2011 Dec 3
Ceramic heater bulb for reptile cages (these can handle moisture and have a very long life, compared to a light bulb).

2011 Dec 3
Ceramic heater won't skunk your beer either, unlike a light bulb :-)

2011 Dec 5
Very interesting... Thanks for all the responses, so many great ideas! And thanks for the tip about beer spoilage. :-D

My husband has graciously offered half of one of the smaller insulated rooms in the garage for me to put the fridges in, now that he has a greenhouse to put hardened off seedlings into this spring. He figures he only needs half the space, especially when I started suggested building things and adding gizmo's the fridges. ;-)

The fridges placed in a room that is about 10C should accomplish what Isabelle suggested, would it not?

2011 Dec 5
If the room is 10C then the fridge will have no problem attaining and retaining its optimum operating temperature - it's if the room falls below the temperature that the fridge should operate at that you'll have problems.

2011 Dec 6
I agree, 10C should be fine, well within operating tolerance for any appliance sold in Canada. And it's warmer outside the fridge than inside the fridge.