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Old 12-11-2010, 07:29 PM   #1
Daniel82
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Default Johnson A419 temp controller issues

I have recieved my new temp controller for fermenting in my chest freezer. I plugged it in and set the set point and everything based of suggestions I found on this site. It was set for 62 with a differential of 1. The compresser turns on the cool it to that temp and turns off at 61 or 60 but it continues to cool the freezer till about 43 degrees and it maintains that temp and wont rise or stay anywhere near my set point. Granted it is an empty freezer but the temp should be a little more regulated than it is. Can someone tell me what my problem is?

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Old 12-11-2010, 08:29 PM   #2
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I have recieved my new temp controller for fermenting in my chest freezer. I plugged it in and set the set point and everything based of suggestions I found on this site. It was set for 62 with a differential of 1. The compresser turns on the cool it to that temp and turns off at 61 or 60 but it continues to cool the freezer till about 43 degrees and it maintains that temp and wont rise or stay anywhere near my set point. Granted it is an empty freezer but the temp should be a little more regulated than it is. Can someone tell me what my problem is?
The problem is that when the compressor is running, the evaporator coils in the walls of the freezer get very cold, but the air in the freezer takes much longer to cool. By the time that the air is cool enough to trigger the controller, the inside walls of the freezer are at zero or below. So, the air continues to cool even though the compressor is off. Try placing the controller probe near the bottom of the freezer, but not touching the walls. The air will be coldest near the floor of the freezer. It may take several hours or more for the temperature to stabilize.
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Old 12-11-2010, 08:31 PM   #3
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put a glass of water in there (or something) and put your temp probe in the water

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Old 12-11-2010, 08:33 PM   #4
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put a glass of water in there (or something) and put your temp probe in the water
IMO, not the thing to do.
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Old 12-11-2010, 08:51 PM   #5
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I find it hard to believe that the coils are so efficient that they can cool the space another 20 degrees even after it cuts off. I think it is more likely the jumper settings are wrong.

Did you set the jumpers on your temp controller correctly?

You want "cooling mode, cut-out at setpoint".



Also just to be sure, this fridge is not sitting out in an unconditioned space in the dead of winter, is it?

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Old 12-11-2010, 09:13 PM   #6
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I find it hard to believe that the coils are so efficient that they can cool the space another 20 degrees even after it cuts off. I think it is more likely the jumper settings are wrong.

Did you set the jumpers on your temp controller correctly?

You want "cooling mode, cut-out at setpoint".



Also just to be sure, this fridge is not sitting out in an unconditioned space in the dead of winter, is it?
It's easy to see what mode the controller is in as there is a symbol for heating or cooling on the display. I think it's snowflake for cooling and a flame for heating. Most of the pre-wired controllers arrive set up in the cooling mode.

It's a freezer and the evaporator coils certainly are capable of cooling to zero and below, and especially so on the initial start up cycle. I would think that if left running for several hours that the temperature swing would be greatly reduced. Putting some kegs in the freezer would also help a lot, but they will also require some time to cool and stabilize.

Actually, I think he would want the compressor to cut-in at the set point and cut-out at the set point minus the differential for cooling. IOW, the compressor should turn on with a rise in temperature.
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Old 12-11-2010, 09:29 PM   #7
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Sounds like you have it in the heating mode

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Old 12-11-2010, 10:36 PM   #8
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No its in cooling it shows the snowflake on the display. I didnt set any of the jumpers as I assumed it was pre-wired for the way I indtended to use it. The temp is rising very slowly like 1-2 degrees an hour its now at 53 with my set point at 61. I'm not sure how easy it is for chest freezers to stay at a temp that high. Its in a storage room in my appt. on the third floor so its not that the temp around it is freezing (I live in MS anyway and nothing freezes here).

I need to look more into the cut-in and cut-out setting. I am about to leave the house for a few hours and if it hasnt regulated more when I get back I may open it up and check to see if it is set correctly.

Thanks for the help guys I was hoping to get this solved by tomorrow because I wanted to brew a new batch and test it out.

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Old 12-12-2010, 01:58 AM   #9
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No its in cooling it shows the snowflake on the display. I didnt set any of the jumpers as I assumed it was pre-wired for the way I indtended to use it. The temp is rising very slowly like 1-2 degrees an hour its now at 53 with my set point at 61. I'm not sure how easy it is for chest freezers to stay at a temp that high. Its in a storage room in my appt. on the third floor so its not that the temp around it is freezing (I live in MS anyway and nothing freezes here).

I need to look more into the cut-in and cut-out setting. I am about to leave the house for a few hours and if it hasnt regulated more when I get back I may open it up and check to see if it is set correctly.

Thanks for the help guys I was hoping to get this solved by tomorrow because I wanted to brew a new batch and test it out.
The freezer just needs time to stabilize. It should settle down by morning. Keep in mind that a freezer does not have a fan to circulate the air inside like most refrigerators do. You can install a fan to circulate the air which is what I have done. Once you get the temp to stabilize, you might consider increasing the differential to something like 3-5 degrees. This will cycle the compressor less frequently for less wear and tear. The air temp in the freezer may fluctuate more, but that is of little concern as the large thermal mass of a keg of beer will only change temperature very slowly and it will settle in at a very stable average temperature. You can check this by pouring a beer and measuring it's temperature. It's no problem for a chest freezer to operate at higher temperatures. The compressor isn't working nearly as much as if it were maintaining sub zero temps.
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Old 12-12-2010, 01:55 PM   #10
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IMO, not the thing to do.
oops.. I meant to say the temp probe of his thermometer, not the controlers temp probe. ( drinking and posting again )
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