Johnson Controller question

I am going to do my first ale in my fridge with johnson controller this weekend and I was wondering what temperature to set the controller at. I was thinking 65* degrees since it has a +/- range of 4*.

Any thoughts/suggestions?

You should be able to set the range (or differential) to your specifications with the note that 1 degree range will have the frig running more often. I use 2 degrees.

As for temp setting, it depends on what you have as a goal. Clean and crisp, go at or slightly below the low end of reccommended for your particular yeast strain. If you want ester, go high end. So its a tough question to answer.

Also, many (myself included) people attach the probe to the side of the fermenter with some insulation between ambient air and the probe except where it contacts the fermenter. This gives a truer reading on the internal temp of the fermenter. Otherwise, you will measure the ambient temperature only and not take into account the exothermic increase in temperature in the fermenter.

I usually set the temp at around 2 degrees lower than I want my beer to ferment at then I periodically check the temp on my fermenter and adjust the controller as necessary to maintain a constant temp.

When I set mine to +/- 2 the chest freezer locked up because it was cycling on and off to quickly and not giving the compressor time to cool. +/- 4 is what I use now and haven't had any problems since.

I use a compressorless refrigerator so I have not had issues with freezing up.

But when I attach the probe to the bucket (I use a cut piece of sock to secure the probe to the side of the fermenter using masking tape) I just set the temperature once and never check it again until I want to take a gravity measurement.

ayoungrad said:

I use a compressorless refrigerator so I have not had issues with freezing up.

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Are we talking about a thermoelectric unit? How cold does it get? I bought a thermoelectric wine cooler and it was doing good to get 20F below ambient temp. I quickly got rid of it.

The unit was an older model so I'm sure thermoelectric technology has gotten better.

NuCool is the brand name. I have not lagered with it yet so we'll see how well it works when I try a lager next month. I'm looking to get to 40 with an ambient of about 75-77. I have heard from others on here that it can be done.

kgraber said:

I am going to do my first ale in my fridge with johnson controller this weekend and I was wondering what temperature to set the controller at. I was thinking 65* degrees since it has a +/- range of 4*.

Any thoughts/suggestions?

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A 4 degree differential is really 2 degrees +/-. If you set the thermostat at 65, 63 should really be considered your target temp. The t-stat will come on at 65 and shut off at 61, which is 63 degrees +/- 2. I generally keep a 4-5 degree differential to keep the compressor from cycling so much.

I usually set my dif to +/- 1, and measure the temp of the beer instead of the ambient temp. The fridge doesn't run that much. The reason I use +/- 1 is because the thermal mass of 5 gal of liquid is resistant to temp change. The way I look at it is that for every degree you let the temp rise, that's 1 more degree that you have to lower the temp when cooling. With a higher dif, the fridge runs less often, but for longer periods of time. I look at it as 6 of one, half a dozen of the other.

As for your situation, I would control the temp with a dif of 1 or 2. Typically, a kolsch is going to be fermented cooler to limit ester production. A dif of 4 might be too much leeway. If your beer spends much of its time at 67-68F as opposed to 65F, you are going you are going to end up with a much different flavor profile. If you want to use a dif of 4, I would recommend setting your temp to around 63F.

509inc said:

When I set mine to +/- 2 the chest freezer locked up because it was cycling on and off to quickly and not giving the compressor time to cool. +/- 4 is what I use now and haven't had any problems since.

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Adjust the anti-short cycle delay.

kgraber said:

I am going to do my first ale in my fridge with johnson controller this weekend and I was wondering what temperature to set the controller at. I was thinking 65* degrees since it has a +/- range of 4*.

Any thoughts/suggestions?

Click to expand...

I'm assuming you've got the analog controller. If so, you'll find your wort stays very close to the midpoint as long as you leave the JC probe monitoring air temp inside the fridge (and not taped to the fermenter as is typically recommended with the digital version).

I always set it to 62 for the first three days of fermentation then go to 65, just to off set the increased fermentation temps. That has worked great for me.

jkarp said:

I'm assuming you've got the analog controller. If so, you'll find your wort stays very close to the midpoint as long as you leave the JC probe monitoring air temp inside the fridge (and not taped to the fermenter as is typically recommended with the digital version).

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I am curious as to why the analog version would behave differently than the digital version. Why not tape it to the fermenter?

bartbert said:

I am curious as to why the analog version would behave differently than the digital version. Why not tape it to the fermenter?

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Because the analog has a hard-wired 4 degree differential. It will cool until 4 degrees below the setpoint and then will shut off until the setpoint is exceeded. If you were to tape the probe to the fermenter, your wort temp would vary by 4 degrees. When the controller is instead managing the air temp of the fridge, the wort mass averages out the swings.

The digital controller allows setting the differential down to one degree. At that point, it's preferable to directly manage the wort temp.

I use a digital one and put the probe in a thermowell. I set the temperature differential to 1 degree with a short cycle delay of 12 minutes.
As I recall, the differential on the analog controllers is fixed at 3 degrees and there is no programmable short cycle delay.
If the temperature is above the set point, the compressor will start, and will remain active until the measured temperature drops to 3 degrees below the set point. (I may be off by 3 degrees here, but the principle is right).
If you tape the sensor to the fermenter, it will effectively read the temperature of the fermenter. If the compressor kicks in when the temperature rises to 68 degrees, but doesn't switch off until the fermenter temperature drops to 65 degrees, then the ambient temperature within the freezer will probably have dropped into the 30's (or lower) by the time the fermenter temperature has dropped to 65. Because the ambient temperature is much lower than the fermenter temperature, the fermenter will continue to cool even after the compressor is switched off.
The overshoot effect is not noticeable with a small differential, but can be substantial with a 3 degree differential.

-a.