We woke up to 3.5degC yesterday morning and the Strong Ale I was fermenting was down to 14degC in the ferm freezer and bubbling a bit slow.
I had a heater pad (30W) that wasn't being used so I connected it to a timer and threw it in alongside. 15 min on then 2 hrs off seems to be working. When it was on fulltime it was getting a little warm.
I control my chest freezer with one of the Jaycar units but I would only recommend it to somebody handy with a soldering iron.
http://www1.jaycar.com.au/productView.asp?...eMax=&SUBCATID=
I went down this path because my freezer has a wierd thermostat that I couldn't remove for fear of wrecking it (and getting bitten by something nasty lurking underneath
)
I removed the thermistor (temperature sensing component - looks like a small blue capacitor) and put it on 500mm of wire which I fed into the freezer. The device is purley resistive and not effected by the extra capacitance of the wire as somebody suggested in a previous thread.
Connected the mains thru' the NC (normally closed) contact because the thermostat is designed for heating. ie freezer turns on when thermostat turns off.
Downsides
of this unit are:
- It displays 'HEAT' when the freezer is actually off but I can live with that.
- If the thermostat malfunctions (stops) it will freeze everything inside.
- It runs off 2 x AAA battreries so I had to build a powersupply - had the parts lying around anyway.
- Only handles 3A inductive loads - my freezer has 1A surge (125W motor) so ok.
- 5 to 30degC range - ok for me, lagers go in the other fridge.
On the good side
it constantly displays the current temp inside the freezer, you can reliably set an exact temperature to 0.5deg resolution & it's very easy to operate.
It has a 'deadband' hysteresis of 1degC (+/- 0.5deg from set point). On a warm 30deg day the pump turns on for 10 or so mins then off for about 45. This may stress the motor slightly more than usual operation but with an old freezer that cost nothing who cares.
Also added a 12VDC fan from an old computer for air circulation but I think it's mentioned elsewhere before also.
Would I go down this path again? Definitely.
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