Fluctuating temperature in Fridge constant

I just put together my fermentation chamber and have a blackberry wine in primary. I’ve set the fridge constant mode to 20c. The fridge probe is taped to the ceiling of the chamber and hangs down about 3 inches. The beer probe is tucked out of the way until I get my thermowell.

The temperature is fluctuating up to 24c and down to 17.5c. Not sure what would cause this but it seems like it’s on an hourly cycle. No idea why it would do this.

How powerful is your heater? The temperature seems to rise very fast.

You also have quite a bit of overshoot in the fridge temperature. Moving the sensor closer to the cooler would help.

Thanks for the reply!

I have a Lasko #100.


It seems to heat up very well. I’ll try moving the probe closer to the fridge and see if that works. I currently have the heater very near the fridge too. I did this to make the two temperature sources be similar distances to the probe.

Right, I wish people would stop recommending these. You are using a 1500W heater to heat up a tiny amount of air.

About 100W is the right amount of power, for example a reptile heater, and much safer.

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1,500watts to heat a fridge?! Come on people!!

I get away with a heat matt of like 40watts :laughing:

To be fair, I’m not using just a fridge. I built a 2x4x2.5 chamber. I didn’t think the 40w reptile heater I also got would be big enough. I’ll give it a try though.

Ive been using 25w. You don’t need much at all. I also run Kp at 5, Ki at 0.1and Kd at 1.5. and have a small pc fan running constantly. With this setup i found the cycling of the fridge and heater to be cut back significantly and don’t have any “heating min time” issues that can come from using excessive wattage.


Thanks @gezzanet. That’s great info to have. I’ll give the heater I have a go and see how it is.