[Jimmy K]

I have a Johnson digital temperature controller hooked up to my new converted freezer kegerator. I'm wondering what controller settings people use. Mostly, I noticed that you can change the temperature differential which I guess is the range from when it shuts off cooling and turns it on again.  The default is 5 degrees, which seems like a wide swing?

[jmcamerlengo]

When I was fermenting in a chest freezer I used a 2 degree differential setting and set the temp 1 degree lower than what i was shooting for on the fermenter.

Need 50 degrees, set it to 49 and it will kick on at 51 and spend the bulk of its time at 50.

[wiley]

My experience has been that the deadband setting for temperature control should consider a number of things, but is typically used to keep from short-cycling the compressor on the fridge/freezer. Short-cycling intervals will vary based upon the specifics of your setup. A couple of factors that can influence your deadband differential are the medium being measured, quality/amount of insulation, and system type. If you're using the typical keezer/kegerator setup, you can bolster the insulation and/or change the medium your probe is measuring.

I've seen kegerators that take a White Labs vial, cut a hole in the lid, put a Ranco probe and water in the vial and seal the lid. This way you're measuring the temperature of a water solution in the kegerator as opposed to the ambient air within.

A 5 degree deadband seems excessive, but may not be if the risk of short-cycling the compressor goes unmitigated.

[Jimmy K]

I had thought about sticking the probe in liquid. I think I'm going to try sticking it in a small block of foam insulation. The idea would be the same, slow the rate at which an air temperature change reaches the probe and turns on the compressor. This way I don't have to worry about a little vial of liquid in there.

[bluesman]

When I was fermenting in a chest freezer I used a 2 degree differential setting and set the temp 1 degree lower than what i was shooting for on the fermenter.

Need 50 degrees, set it to 49 and it will kick on at 51 and spend the bulk of its time at 50.

+1

I also use a 2 degree differential.

I use 40F setting for my kegerator, 35F for my lagering chest, 62-68F for ales and 45-50F for lagers in my fermentation chamber.

[Jimmy K]

Thanks Jason & Ron,
Any other settings I should care about? I didn't expect it to have so many options.

[richardt]

I too use the 2-degree differential to limit short-cycling.
I place the probe on the outside of the fermentation bucket.
To shield the probe from the air and ensure a more reliable reading, I fold up a paper towel several times to create an insulated pocket around the probe and secure the "probe pouch" to the plastic fermentation bucket with packing tape.  It is best done when the bucket is dry and at ambient temps.  When the bucket is cold and damp from condensation, it is harder to get the tape to secure to the bucket.

[bigchicken]

Freezer compressors are not the quality they once were. Try to avoid short cycles to maximize compressor life. As mentioned above, probe placement will be the key. A friend of mine burned up 3 cheap freezers due to issues like short cycling. Of course,  he wasn't paying much more for his freezers than the cost of his temp controller.

[euge]

I don't think immersing the probe in a liquid other than that which is fermenting is a good idea. You want the probe to respond more quickly so hanging in the air or next to the fermenter is better.

[tygo]

I too use the 2-degree differential to limit short-cycling.
I place the probe on the outside of the fermentation bucket.
To shield the probe from the air and ensure a more reliable reading, I fold up a paper towel several times to create an insulated pocket around the probe and secure the "probe pouch" to the plastic fermentation bucket with packing tape.  It is best done when the bucket is dry and at ambient temps.  When the bucket is cold and damp from condensation, it is harder to get the tape to secure to the bucket.

This is what I do except I use a sheet of thin styrofoam packing stuff instead of paper towels.

[tom]

 If you insulate the probe (or use a thermowell) so it is measuring the actual fermentation temperature I set my differential to 1degF.

I had thought about sticking the probe in liquid. I think I'm going to try sticking it in a small block of foam insulation. The idea would be the same, slow the rate at which an air temperature change reaches the probe and turns on the compressor. This way I don't have to worry about a little vial of liquid in there.

[wiley]

I don't think immersing the probe in a liquid other than that which is fermenting is a good idea. You want the probe to respond more quickly so hanging in the air or next to the fermenter is better.

If we’re talking about fermentation (which the OP didn’t address), then first choice would be to measure the temperature of the actual fermentation. See below:

http://morebeer.com/view_product/6666//5_Gallon_Hood_Thermowell_also_3_and_6_gallon
http://morebeer.com/view_product/16672//Stopper_Thermowell

When you're measuring the actual temperature of the fermentation (to Euge's point), you're increasing the control accuracy, and narrowing the variance between actual fermentation temperature and the temperature at which the fermentation environment is controlled. This point we agree on.

If you can't measure the actual fermentation temperature, I think it’s better to measure a medium that is characteristically similar to the fermentation (i.e. water). Yes, this can present some logistical challenges, but provides a better buffer so as to not short-cycle your compressor, and is a better proxy for the environment in which you're fermenting.

Measuring the ambient air temperature of the environment would be third. As mtnrockhopper described, it’s best to insulate the probe if you’re measuring the ambient air. Using an un-insulated probe to measure the ambient air temperature increases the risk and likelihood that the probe would sense rapid temperature spikes (think opening the refrigerator door) in the fermentation environment, and could result in short-cycling and lower than expected actual fermentation temperatures.

While accuracy of temperature control and probe response are important, maintaining the health of your equipment is (IMO) more important. The value of my time spent in setting up and configuring equipment is (in general) worth almost as much as the equipment itself.

[euge]

Luckily the OP has a chest freezer. Much less likely to lose air when the lid is opened.

Also went with a chest freezer. I hang the probe in the air since there's two fermenters in there. And a small case fan to gently stir the air around for convection purposes. 

My beer is always at the temp the controller is set at.

[Jimmy K]

I am talking about a kegerator for serving beer, not fermenting. I did change the settings last week after reading responses - 37 with a 3 degree differential, and I stuck the probe in a block of foam.

[richardt]

... To shield the probe from the air and ensure a more reliable reading, I fold up a paper towel several times to create an insulated pocket around the probe and secure the "probe pouch" to the plastic fermentation bucket with packing tape...

This is what I do except I use a sheet of thin styrofoam packing stuff instead of paper towels.

That'd work well, too.  I use whatever I got laying around the garage.  Usually the roll of paper towels is the first thing I see.