Insulated Ducting vs. Mini Fridge

[manoaction]

So…

In my little brew area, I’ve got my trusty old upright fridge and it sits next to a counter top.

I’d like to make a cold box area under that counter top.

I was thinking about the concept of running some insulated flexible ducting to the insulated area, rather than tearing apart a mini fridge.

I could hook a computer fan to the duct and suck 50 CFM and thread a return line from the other side of the box, through the duct and back into the freezer side of the fridge. Maybe I could even hook the temp controller to the computer fan. The ducting is R6 which isn't bad. Maybe I could double wall it for extra effectiveness if need be.

I suppose I could easily over size that freezer space though… Thoughts?

 

[brick]

Could work if the space is small and your sealing/insulating are super tight. The problem you might run into is that the cooling load may exceed what refrigerant loop is sized for. If that happens then 1) the space wouldn't be as cold as you want and 2) the compressor would eventually overheat and fail. But that's just stuff to look out for, not a prediction of failure. If you are willing to take a risk then I'd say give it a shot. Insulate and air-seal the entire system like your life depends on it.

 

[manoaction]

Is there a generally accepted max size for a compressor strength? Any way to make estimates?

 

[brick]

One thing that occurs to me is that heat transfer wouldn't be all that great between the air that you want to move to/from the cool box and the evaporator coil that is probably behind a solid surface in your fridge. An A/C system works well because the coil is in the air stream with lots of fins. You get away with shrouding the evaporator in a fridge because air isn't supposed to be moving at all. So I'm less optimistic than I was yesterday. The ducting thing might be more of a gamble than it's worth.

 

[jamesseth]

I've been doing something similar for a fermentation chamber. I only keep it at 68 degrees, but it holds very nicely. I have a standard upright fridge and use two computer fans hooked to a temperature control (one pulling and one pushing through an insulated duct). The chamber is 45" x 37" x 30", but haven't had any trouble keeping it cool.

 

[mabrungard]

I use a similar configuration to chill my fermentation chamber. Insulated ducts connected to the freezer compartment of my beer fridge with a thermostatically-controlled computer fan within one duct controlling the temperature in the chamber. It works beautifully and still leaves the freezer compartment fully functioning. One note is that my fridge is a 25 cf unit, so it has plenty of cooling capacity. The fermentation chamber is fairly large at about 25 cf.