Any sparky's here? Need wiring advice for fridge thermostat.

[denimglen]

Bought the two stage, heating and cooling, tempmate thermostat. I'd like to have a fan to circulate air inside the fridge. I'd like it to turn on when the heating side or cooling side is in operation.

Ok nicked this pic from someone on AHB and added my bits that connect to the fan.

Just to clarify I'll need a diode in the spots marked 'A' and 'B'? Otherwise when the cooling side turns on the heating side will turn on and vice-versa? If this is right what sort of diode do I need and where do I find one?

Cheeeeeeeeers.

[Sparky]

Excellent drawing there.

The diodes would only be useful if you were using a DC supply. Standard supply here is AC and your compressor requires AC. Putting diodes where you indicate will destroy the compressor very quickly due to halfwaving.

I have two fermenting fridges and each uses a controller to switch the fridge compressor. The sensor sits inside a thermowell (pocket) that goes into the fermenter. This method ensures that the wort temperature is measured and the compressor runs (via the fridge thermostat set at lowest setting) to control fermentation temp.

I wouldn't bother with the fan. You could try setting a differential of maybe 0.3 - 0.5 deg to ensure minimum overshoot of the setpoint.

ie; enter a setpoint of 19.0 deg and wort temp will average around 18.8 - 18.9.

Keeps it simple and works very well for me.

[studio1]

Cool - don't spose you could put up some pics of your thermowell?

[Sparky]

Unfortunately both are in use, so I can't show you the full thing, however the pocket is welded into a CIP blank that sits on top of the fermenter. The well is approx 300mm deep and the temperature probe sits inside.

Cheers

[denimglen]

Cheers Sparky!

Yeah, those DIY DSE kits and 6th form physics really only teach you DC, haha didn't even click that it was AC.

I'm not going to use a thermowell yet. Apparently the tempmate will have a probe that's long enough to be submersed soon so will grab that when it comes out. For the moment I'll just tape it to the side of the fermenter and put some rags or something on the air side of the sensor to insulate, not perfect but will be heaps better than the stupid water bath and fan thing that I'm using at the moment.

I've heard some good things about using a fan. I'll see how it goes without it first, was suggested to me on AHB to just wire up a computer fan and run it 24/7. I'll just dodgy that up with the DC adaptor I just got from throwing out my scanner haha.

Thanks again mate.

[Mike Neilson]

FYI; I have my Probe tape to the side of my fermenter with a piece of Poly 1 1/2 thick. I had the temp set at 18.5 with a .5 deg dif setting. I took a gravity reading, temp reading. The Tempmate said it was at 18.8 and my manual digital reading was 18.9!! not bad I say it might not be as flash looking as a thermowell but It sure works, just like a coat hanger for a car aerial!!

[denimglen]

Haha yeah, and one less thing to sanitise.

A few times I've dropped my digi thermometer into the fermenting wort and it matches up with those thermometer strips on the side.

I guess most of our fermenters are not wide enough in diameter for it to matter too much.

[Sparky]

Cheers

I'm sure you'll be fine and won't need the fan, the method that Mike uses will work fine too.