New fridge, need help


I have replaced my horrible broken old fridge with a new one. This new one (Tefcold SDU1375) is quite a different beast than my old one and is much more powerful as such.
I wanted to try and not tamper with the fridge’s hardware, but I’m running into trouble with temperature control. The fridge has 7 settings, 1 through 7, which the manual says correspond with 2-12 celcius. It’s on 4 at the moment, which already allows the fridge to become super cold, and is causing oscillation in the beer temp. The fridge is only on for the minimum ON time in brewblox, but in those 3 minutes, the fridge temp drops 4 degrees and the beer 0.7c. Too much swing for me. Anything I can do? Can I make the fridge less powerful?


How have you wired your fridge, that it still responds to its native controls?

The blunt-force approach would be to leave the door ajar, but you can also reduce the minimum on time.

The minimum off time is required for the compressor, but minimun on is only configured to make efficient use of the fridge.

Yes, still wired to native controls. Basically plugged it into the ssr connected to the spark.

I thought minimum on time was also a protection - I’ll now set it to 2 minutes iso 3. Thanks!

If native controls are still in place, you may want to keep an eye on the fridge’s behavior. Brewblox being first in line will guarantee the minimum off time being respected, but native controls may choose to turn off the compressor while it still is supposed to be enabled.

I don’t expect this to happen at fermentation temperatures, but it may interfere with cold crashing.

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Minimum off time is more important to prevent damage to the compressor.
When the compressor builds up pressure, it needs to equalise. Quick cycling does not give the compressor enough time for pressure to drop and can cause pressure to run too high.

Also don’t place your fermenter against the back of the fridge. This will let the fridge cool the beer directly instead of through the buffer of the fridge air.

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If you don’t want to mess with the fridge thermostat, you just have to control power. Two options are:

  1. SSR from, brewpi controls the input signal, buy a cheap extension cord and strip the hot wire to connect to the load side of the SSR

  2. Power Relay Module use brewpi output pins to control the power outlet. Very much the same as above but without the hassle of stripping and connecting 120V wires.

It would still be limited by the fridge’s own thermometer right?

Yes. He suggests two approaches for how to control the fridge power supply with Spark IO.
You’re currently using his option 1.

@andylytical For the power relay module, are you aware of a 230V / euro plug alternative?

This is only a problem for cold crashing though. You cannot go colder than the lowest temperature the fridge allows. Controlling fermentation around 20C will not be a problem.

Sorry, I do not know of anything. The item I linked above looks like it’s made by (or at least sourced from) and they appear to be a US based company. I can only assume they are targeting only the domestic market. Too bad, it’s a good idea that allows digital control without any need for custom wiring.

Change ton thermostat par un model plus “presise”

cordialement Yannick

Could you please take screenshots of your PID graphs, and post that?