Using a PID to control fermentation temp

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David Woods said:
I know this is a very old thread but did anyone ever have any more thoughts on this? anyone tried it? I have decided to have a go at using an STC for the cooling side with the STC probe taped to the FV and a PID controlling the heater with the probe measuring the space. I am feeling that in using the STC for both I have found as the OP said that the heater over runs the temp a lot so figured this would be worth a try with the PID "learning" the space . Was wondering about how to set the temps for each of the controllers so they are not fighting each other.

Any thoughts?
Click to expand...
I can confirm that everything in this thread about "temperatures over-runing" and the fridge/heater "fighting each other" is complete myth. So if you haven't yet forked out for a PID, I personally wouldn't bother.

I have two under-counter fridges both fitted with ITC-1000 controllers and 60W tube heaters; been using them religiously for the last 18 months. It is physically impossible for a 60W tube heater to cause 20L+ of beer to climb past a setpoint. Absolutely impossible with the temp probe stuck to the side of the FV and insulated from ambient. I know this because I've watched it scores of times on hot days, cold days, rainy days, Tuesdays...

dS - 0.5C-1C
cd - 10 minutes

With the above settings in both my setups there is zero issue.

Maybe I'm missing something, or overlooking an error that I'm lucky enough to not be doing?
 
Last edited:
Hi, I think the OPs point and mine is that when the heater kicks in and the stat reaches temp then the heater turns off there is a lot of residual heat so the temp maybe keeps on rising so then the cooling kicks in and so on.

I take your point and I was thinking for the sake of £10 PID would that be better - but not having tried it I am happy to hear this may not be the case - just wondered if anybody had tried it.

Cheers
 
David Woods said:
Hi, I think the OPs point and mine is that when the heater kicks in and the stat reaches temp then the heater turns off there is a lot of residual heat so the temp maybe keeps on rising so then the cooling kicks in and so on.

I take your point and I was thinking for the sake of £10 PID would that be better - but not having tried it I am happy to hear this may not be the case - just wondered if anybody had tried it.

Cheers
Click to expand...
There's not much residual heat, certainly not when talking relative to the volume of liquid. Remember that a liquid medium such as 23L of wort really needs a lot of energy to heat or cool it. This happens over quite a while also.

With the dS set at a minimum of 0.5C, you won't see any issues. I've yet to see overshoot either. This is why I'm quite confused. With a dS of 0, I can forsee issues of course - but that's obvious.

I understand your thoughts, and before I built mine I did think something similar for a very short while. Try without the PID and see how you go. I'm sure you'll realise there's no issue and save a tenner. Should you somehow find mad temperature swings and other aspects of craziness going on, then you could always buy a PID to fix whatever may be amiss?
 

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