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texbrewer 09-05-2010 04:27 AM

Trouble setting up johnson controls a419
I just bought a Holiday 5.0 cubic ft chest freezer to ferment and store. I want to make sure that I am setting my Johnson Controls A419 thermostat correctly. I am brand new to this contraption, so any help would be appreciated!

I am going to brew and ale that needs to be fermented at 68 degrees. How should I set the SP, Diff, and ASD? Maybe a little more explanation of how these controls work (I need the dumbed down version please!). I have set the jumpers to cut-out at the set temp.


Drbobcat 09-05-2010 07:30 AM

I have the same freezer and controller. To ferment at 68 degrees I would set my controller to SP of 67*, Diff to 1*, and the ASD to max (12 minutes). The set point is the temperature you want to maintain, the differential is the acceptable range for the controller...so if the set point is 68* the the freezer won't be turned on until the the unit is over 69* and it will be turned off at 67*, the ASD (anti short cycle) prevents the freezer from being turned on too frequently and burning out the motor. I happen to set my unit 1 degree colder than my fermentation temperature because that is what works for me. You will need to experiment with your unit. Whether you want to put your probe in a thermowell or attach it to the side of your fermenter is another issue. There are plenty of posts about that, I personally attach it to the side of my fermenter.
Good Luck and have a blast with the new toys.

texbrewer 09-08-2010 02:27 AM

So, I have been messing with the unit, but it keeps dipping into the high fifties. What about my freezer settings? I have it set to it's lowest setting, but I figured that wouldn't matter. I don't mind one or two degrees off but we are talking ten! Am I missing something?

SP set to 68, Diff 2, ASD 12

Drbobcat 09-09-2010 07:27 AM

Your freezer settings shouldn't make any difference. With a Diff of 2* you should be reading anywhere from 66-70* (that's why I keep mine set at 1*). Where is your probe in the freezer? I personally am a fan of taping the probe to the side of my fermenter and covering the probe with some type of insulation. If the probe is just hanging in the air or right next to one of the freezer walls, it can have weird readings or if it is in a large bottler of water, it can take a while for the water(wort) to change temperature at the level of the probe and this can sometimes lead to large temperature fluctuations. Realize there are a lot of difffering opinions on this one, so again you need to see what works for you.

Flic 09-10-2010 02:28 AM

+1 on Drbobcats recommendation to tape the probe to the side of your fermenter. I have the same controller and tape it to my bucket and then tape some bubble wrap over top of it. I also set my temp to 1 degree below targeted fermentation temp and I use a differential of 1 degree. Temp stays right on, I'm actually amazed how well it works. Before I was taping the probe, I had it hanging down in the freezer and was having huge temp shifts. Tape it, insulate it and you're good to go!!

Brewham 09-10-2010 03:07 AM

I put the probe on the side of the bucket and taped a folded over (several times) dishtowel on top of it as a blanket. Set the add-on thermostat to 69* with 1* tolerance. Set the freezer thermostat to the highest temperature - not that it makes a difference since the external thermo sets the temp but as a safety in case something goes wrong maybe it won't freeze my beer.

Wreck99 07-17-2012 02:44 AM

I just got one of these and hooked it up. Still experimenting with the settings to get it right. Is it wrong to put the probe in a glass of water?

day_trippr 07-17-2012 02:58 AM


Originally Posted by Wreck99 (Post 4256892)
I just got one of these and hooked it up. Still experimenting with the settings to get it right. Is it wrong to put the probe in a glass of water?

The probe is not waterproof. Strap it to whatever you're trying to keep cool and cover it with a piece of insulating foam...


new2brew32 07-19-2012 02:53 PM

You have to adjust the jumpers from the factory settings. You have to unplug the unit and open it up. Once you locate the jumpers you set them to cooling mode cut out at set point (the top jumper over to the left). This allows you te set a point for the cooler to turn on at a certain temp and then turn off at another temp. I set my set point at 65 and my differential to 3. At 68 the cooler engages then shuts off once it reaches 65. Other wise it just cools and doesn't stay at a certain temp.

arnoldk2 07-19-2012 03:04 PM

Technically you are suppose to adjust the jumpers. I'm to lazy for that. The way I set mine up is a bit backwards. I have a 2* differiential. So let's say I want to ferment at 65 degrees. I set my set point at 66 degrees. At 66 degrees it kicks my fridge on and cools it down to 64 and then it shuts off. Theoritically the average temp in the fridge should be 65 degrees over the time your beer is fermenting.

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