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Home Brew Forums > Home Brewing Beer > DIY Projects > Fermenters > Possible issue with Johnson A419
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Old 06-14-2011, 09:06 PM   #1
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Default Possible issue with Johnson A419

I bought a controller for my freezer. The initial set up was:

Set point: 71
Dif: 2

The freezer got to 69 and the controller kicked on. When the controller turned off, it was registering 62 for a ~9 temp spread. It doesn't seem like this controller has much to it, so it shouldn't be too complicated to set up. Has anyone seen this in the past? I've just got it dangling in my freezer for now, so it's only picking up the ambient temp. I wanted to test it before doing my first batch this weekend.

Thanks!

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Old 06-14-2011, 10:01 PM   #2
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With this setting, it should turn the freezer on at 71, and turn it off at 69.

It is odd that it starts at 69 for you. Did you check that the offset is at 0 ?

Did you test this in an empty freezer ? it might explain why you reached 62. The air gets cold very quickly if there is nothing else. Also, the wall of the freezer gets very cold too. So if the probe is touching the wall, it will become cold very quickly.

I would say go ahead, and fill the freezer with beer. Plug everything, and let it settle at the right temperature overnight. The next day, see what the temperature is. It should be much more stable once it is full.

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Old 06-15-2011, 12:21 AM   #3
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Quote:
Originally Posted by mperceau View Post
It is odd that it starts at 69 for you. Did you check that the offset is at 0 ?
The offset is at 0. I just got home and it's at 67 right now. I'm not sure when the last time the freezer kicked on. This morning I was watching and it was flashing between 68 and 69, but very quickly; it was like it was just on the line of 69 and it would turn on.


Quote:
Did you test this in an empty freezer ? it might explain why you reached 62.
The freezer is empty. I wanted to make sure that the probe worked, but you could be right. I don't have it touching anything, but there is a fan in the freezer blowing that I put in there (a pc fan).

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Old 07-10-2011, 07:23 AM   #4
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Empty I am getting 10+ degree fluctuations. I have the probe insulated and taped to the wall.

Will 4-6gallons of liquid actually stabilize it?

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Old 07-10-2011, 07:46 AM   #5
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Originally Posted by checkii View Post

Will 4-6gallons of liquid actually stabilize it?
Yes.
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Old 07-10-2011, 08:13 AM   #6
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When you put the beer in it, you'll want to tape and insulate it against the side of the fermentor instead.

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Old 07-10-2011, 09:13 AM   #7
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Originally Posted by emjay View Post
When you put the beer in it, you'll want to tape and insulate it against the side of the fermentor instead.
i was planning on running a remote thermometer into a thermowell and calibrate the temp controller based on that. and leave the controller insulated and taped to the wall.
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Old 07-10-2011, 09:24 AM   #8
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Quote:
Originally Posted by checkii

i was planning on running a remote thermometer into a thermowell and calibrate the temp controller based on that. and leave the controller insulated and taped to the wall.
Thing is, the walls are the coldest part of the freezer, because the coils are directly behind them (mine develops ice even with a 70° ferm temp...)

Also, it's impossible to calibrate. Fermentation temps can jump up as much as 10 degrees above ambient, but they are never consistent, and the gap will change depending on yeast activity. It could be 8° above ambient one day, and then only 2° above ambient the next day - how do you calibrate it when the difference is constantly moving, without having to do it several times per day?

Remember, you want to control the temperature INSIDE the fermentor, not outside. The only effective way to do this, given the fact that yeast activity generates its own heat, is to have the controller know what the temperature is like INSIDE IT. If you have a carboy, the best way is to just put the probe inside a thermowell, but if you're just using a plastic bucket, you can still get accurate temperatures by taping the probe against the side of the fermentor (below the surface of the beer, of course), and insulating it.
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