0.5 Overshoot in Beer Temp


Just wondering if anyone can explain the 0.5 overshoot on beer temp. This appears to have happened at the most active point in fermentation. Until then appears to have been holding temperature within 0.1 which was great.

Settings below.

Beer-to-Fridge proportional gain (Kp) = 10 (It was set to 2, i think but changed this morning after reading another community post)
Beer-to-Fridge integral time constant (Ti) = 7200
Beer-to-Fridge derivative time constant (Td) = 1200
Maximum difference between fridge and beer set point (= output of PID) = 10
Beer-to-Fridge Input filter delay time = 18
Beer-to-Fridge Derivative filter delay time = 318 (again changed this morning based on a previous post think it was set to 4)
Cooler proportional gain (Kp) = 10
Cooler integral time constant (Ti) = 1800
Cooler derivative time constant (Td) = 200

Fermentation is in SS Brewtech Brewmaster Conical Fermentor 14GL, larder fridge(controlled fully by BrewPI), with tube heater, thermowell in fermenter with temp probe inserted.

I also have water chiller that i can run cooled water through the Fermentor coil controlled by Electronic Ball valve but don’t use this at the moment for controlled cooling by BrewPI. However I ran it for about 10seconds to bring the temperature down from 19.5 to 18.9 just incase you are wondering about the quick temperature correction and also the spike in Fridge setting was as a result of my changes as mentioned above.

Any help with the above would be greatly appreciated. Worth saying that since I made the changes to beer fridge KP and also B2F derivative delay as above seems to be holding beer temp within 0.1 but just want to make sure I’ve made the right changes, as obviously i made these based on a previous community post and that individuals setup and graph data was slightly different to mine (0.3 overshoot v’s 0.5).



The actuators did what they needed to do to keep the fridge temp at the fridge setpoint.
It looks like the fridge setpoint needed to be lower, which is managed by the beer-to-fridge PID.
A higher Kp there will result in more difference. So I think you made the right change.

You can let brewpi cool by switching the pump for cold water on and off and omit the valve. That’s what I do myself. It works well with a very short PWM period of 1 or 2 minutes.

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Thanks Elco

Seems to be running nicely now. On a related point, i’ve now implemented a 140mm fan inside the fridge for air distribution. One of the issues i have at the moment is I don’t have a the short sensor probe (just ordered one and the panel mount) so at the moment my fridge temperature probe comes in through the drain hole and is sitting about 2-3 inches from the back wall of the fridge but crucially its at the bottom of the fridge so i’m fearful that the tube heater at the bottom is interfering with the fridge temperature. If I implement the fan and have it at the bottom of the fridge blowing the air upwards will this be ok or do i need to place the probe in some water. Ive attached a picture showing how i’ve planned to do this, don’t know if the water amount is too small. At present the actual fridge temp seems to reflect the beer temp(19.0) with the constant being a bit lower with the probe in that small amount of water. Should i go with the probe in the water(this amount or more) or just leave it free in the fridge. My plan is to get a shorter probe and mount it further up in the fridge near the lighting unit.


Brewpi Fermentation Chamber Setup

It’s hard to comment on your graph with the beer temp not displayed.

I’d add a wall mount RJ12 coupler and then use a short 10cm probe in that.

oops added now sorry.

Now I’m just wondering why your beer name needed censoring :slight_smile:

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Ha Ha, was just cause it had my brewery name in it and I wasn’t sure if you were sensitive about free advertising :-). Ive pulled the fridge probe out the water and just have it as before but now with the fan circulating air. I’m assuming the fan circulating the air will avoid any obvious hot/cold spot that would interfere with correct probe temp reading(well at least that appears to be the case) seems to be all working spot on. Got the short probe etc ordered so i’ll get that all sorted when it arrives.

Got your order for the probe and RJ12 coupler.
Do you maybe also need a cable to go from spark to coupler? https://store.brewpi.com/temperature-control/cables

Ahh yes brilliant hadn’t realised you did those i was going to make my own but that would save a lot of hassle. I’ll stick an order in for one of the 3m length ones.