Help with fridge - kegerator conversion

[JonA]

Any techies help me with a fridge to kegerator conversion please...

I'm helping a friend to make a kegerator for his beer storage and also to give better control of his fermentation temperature in the summer months. He has bought a basic fridge and an E-1000 control unit, and we've managed to drill various holes in the fridge without losing all the gas! So far, so good.

Years ago, when I built my kegerator from an old Frgidaire upright fridge, the electrics conversion was pretty simple. The fridge thermostat was basically just a mechanical on-off switch so I just shorted the thermostat terminals and the compressor would then run permanently when the fridge was plugged in.

I built a little control box for my STC-1000 with a chunky relay to handle the compressor start and put a 13A socket on it, plugged in the doctored fridge to my control box and it all worked fine ever since.

However, things are a little different on the new fridge - behind the thermostat wheel is a control board, then next to the motor is another control board - realised now that it's got an inverter compressor driven by an IPM (intelligent power module).

We've put a scope on the control input wire to the IPM and it looks like it's carrying a PWM (pulse width modulation) low voltage DC signal and the inverter compressor is star wired 3 phase so you can't power it directly from the mains, you have to use the IPM.

So, before we start fiddling with the IPM control input and risk damaging it, can I ask if anyone has successfully converted an inverter fridge to work with a STC-1000 / E-1000 control box? and if so, what did you do in order to make the IPM drive the compressor at 100% all the time?

It would appear that fridge manufacturers are all moving towards inverter compressors as it gives better energy efficiency ratings, so this issue will probably come up more in the future.

Thanks for any help.

[Cobnut]

Why not keep it simple and switch the fridge off and on using the stc-1000 and leave the thermostat intact, but set to “cold”? No need to mess with the stat.

I have 3 fridges configured like this, 2 of which also have tubular heaters in the bottom so I can maintain a steady fermentation or storage temperature all have been working this way for a couple of years or more without issue.

[JonA]

That's cool if you have done that and they are working ok. Probably me getting too close to the problem and not stepping back.

Certainly a simpler option than messing with the electronics of the fridge. Thanks a lot

[guypettigrew]

Fermentation temperature is usually around 20C. Your friend's 'fridge won't need to work very hard to maintain this during the hotter months.

Just getting it to turn on and off, as Cobnut suggests, should be fine.

You can probably leave the 'fridge thermostat wherever you want-it won't be calibrated to 20C!!

Guy