Efficiency / Duty Cycle of Mini-Fridge Fermentation Chamber

How do you measure the efficiency / duty cycle (on time vs off time) of your ferm chamber?

I just build a box out of 1" foam to fit over the opening of my mini fidge (door removed) and am using a temperature controller to regulate the power to the fridge.

Without sitting around for a bit and listening to it to measure on/off times, how do you all measure the efficiency / duty cycle of yours? Do monitor the power on via computer and plot it? Or do you not care as long as it holds temps

I used one of those Kill a Watt meters over a couple days. Note that my cold box is used as a kegerator down to about 38 degrees F. Heres the text copied from my bar build link in my signature...

Given:
-0.75 KWh in approximately 35 hours
-I noticed the KillAWatt reading 85 watts while the compressor was running
-Fridge set at approximately 3.5 (out of 5)
-Internal temp at approximately 37 deg F
-A corny keg, carboy, and 2 gallon pitcher full of 37 deg F water
-Opened fridge 4 times during the day

(0.75kWh x 1000W/kW) / 85W = 8.9 hours total run time.

(8.9 hrs x 60 min/hr) / 35 hrs = 15 min/hr.

Click to expand...

Of course, the only way to really know the duty cycle is to either sit around and listen to it turn on and off, or get some sort of meter that tracks power usage vs time. I admit I have sat down there with everything off except the fridge and I seem to remember that its likes to run for 8-10 minute intervals. With the above math, I guess the cycle would go something like this for any average given hour: 0-10 minutes ON, 11-30 minutes OFF, 31-40 minutes ON, 41-60 minutes OFF, and repeat.

Or course this rudimentary drunken math is probably way off base. The answer to your question is that I don't care because it is holding temp!

Get an old style motor driven analog electric clock (do they make these any more?). Plug it into the same outlet the fridge is plugged into (might need a multi-tap adapter thingee). Set the clock for 12:00. Come back 12 hours later and see how many hours the clock 'logged'. If it's at 6:00, that is a 50% duty cycle.

-kenc