Thermostat temperature swings due to differential setting

[djonesax]

This is my first brew in my fermentation chamber and I was wondering about the temp differential. By default the thermostat (inkbirds stc-1000 mod) has a 3 degree differential. So I had the probe taped and insulated on the side of the fermenter with the temp set at 65f and it would kick back on when it raised to 68f. It has only been in the fermenter for 24 hours but I decided to set the differential to 1 degree to avoid the temp varying so much.

By the way, the yeast is us-05 and its an american amber ale recipe.

I was just wondering how others set their thermostats and what if any effect the 3 degree swings would have on the yeast?

David

 

[PoppinCaps]

I used to do 2 degrees, now do 1 degree with coolant jacket, notice no difference. If it makes sense for safely cycling the heating/cooling system, within the ideal bounds of the yeast, I doubt 3 degrees will make much difference since the bulk of time it will be around average of the differential.

 

[SpeedYellow]

This is the reason why taping the probe to a fermenter makes so little sense to me. If you leave the probe in the air, set the differential to around 3 degrees F; you'll get very little variation in beer temp and won't overwork your compressor. But if you use a thermowell to measure beer temp, then set the differential to 0.5F to avoid big swings in beer temp. If you tape the probe to the fermenter, what temp are you reading exactly -- the air, the beer, or something in between? There's no universal answer to that question (depends on many factors), so it's hard to suggest a "best" differential.

 

[PoppinCaps]

Djones, what kind of chamber do you have? I think that makes the most difference in the ideal parameters.

 

[raouliii]

I position the sensor on the exterior of my glass fermenter, under a piece of closed cell pipe insulation. I have verified that it reads the wort temperature. The wort temperature is what we are trying to control after all. Not air temperature.

 

[Gavin C]

I do the same.

Set my hysteresis to 0.3C

Wort temp is always in that range of target +/- 0.3C

Fermentation is exothermic so monitoring the chamber temperature is pointless. It's the beer you want to monitor.

Tape the probe to the FV. Insulate it from the cahmber's temperature and set the hysteresis as small as possible

 

[PoppinCaps]

Yeah, this is a to each their own kind of debate, but I agree, you have to know the beer temp. With 5 gallons, I doubt (and it's been shown) there is little difference between the inner beer temp and the outside surface of the vessel. But if you're only controlling the air temp, the yeast might in some cases drive up the heat at a rate the chamber can't keep up with. That's why I've always controlled the vessel temp with heat or chilled glycol wrap measuring temp with a thermowell, and cared very little what the exact air condition outside was, as long as it was above/below the target (depending on how the vessel temp was controlled).

 

[djonesax]

Djones, what kind of chamber do you have? I think that makes the most difference in the ideal parameters.

It's a converted beverage fridge with an embedded STC-1000 controlling the power.

 

[djonesax]

This is how I insulated it. This is an old pic when I tested with water but I am using the same bud-light coozie.

 

[Gavin C]

That should work nicely with the probe in contact with the walls of the FV and the coozie insulating.

 

[SpeedYellow]

This is how I insulated it. This is an old pic when I tested with water but I am using the same bud-light coozie.

*If* you've confirmed that your probe is measuring essentially the beer temp, then you want to use a 0.3C / 0.5F differential. But plastic is a poor conductor of heat, so you'd definitely want to calibrate your probe, and then check it against the actual liquid temp in the fermenter.