Using small fridge for stable fermentation chamber

[ImperialStout]

Thinking of getting a small dorm style fridge at a local yard sale for $20. Plan to use it to create a stable temperature chamber to ferment a 5 gal batch. Once brewing is over it can be used to chill 2 to 4 cases of beer.

Only make ale. Most recipes call for about 68 F. Is it likely the thermostat in a small dorm style fridge can be set to 68 +/- without any modification?

Most fermentation / kegging fridges on this site have external thermostats added. Why is an external thermostat added?

Is it likely the escaping CO2 during fermentation will create too much pressure inside the small fridge and prevent CO2 in the later stages of fermentation from escaping from the fermentation bucket? I think not but wanted to ask in case others have experienced a problem.

 

[bomberman]

From what I understand an external thermostat works by kicking on the compressor as needed, which maintains a temperature that you might not be able to obtain with a fridge's built-in thermostat. I would think 68 is too high for a fridge like that, which is where the controller would come in handy.

I'm not sure about the CO2 question but I can't imagine it being a problem. You could always open the door once in awhile to let some out.

 

[DoubleAught]

From what I understand an external thermostat works by kicking on the compressor as needed, which maintains a temperature that you might not be able to obtain with a fridge's built-in thermostat. I would think 68 is too high for a fridge like that, which is where the controller would come in handy.

I'm not sure about the CO2 question but I can't imagine it being a problem. You could always open the door once in awhile to let some out.

This

 

[Dogphish]

you will almost certainly need a $50 temperature controller to keep the fridge at 68 degrees. that fridge/thermostat is designed to operate at lagering temperatures and below.

i bet that the seal on the fridge will let out any CO2 pressure before it builds up and causes a problem too. don't worry about that.

 

[FoundersBrew]

I use a small fridge, but I had to take the shelves off the door to get it to close. I use a Johnson thermostat.

 

[BetterSense]

There are threads here about turning the temperature up that far but you usually have to modify the thermostat and it's not a sure thing.

I wondered about the CO2 thing as well. I don't know because I don't have any fancy fermentation fridges.

 

[gr8shandini]

I definitely wouldn't worry about the CO2. If the door seal was airtight, you'd never be able to open one once it cooled. Say your mini-fridge had a 15 x 20" door. That's 300 square inches. Even a half a psi differential would make it a bear to get open.

As for the temperature controller, go ahead and get one if your budget allows. Even if you were able to modify the built in thermostat, it's nice to be able to precisely control the temp over a fairly wide range.