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Old 12-16-2009, 03:42 PM   #1
kal
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I use the analog Johnson temp controller in my keg freezer (see pic below). Is it possible to set the differential (hysteresis) on these models? How?

Northern Brewer states that it has a 3.5 degree F differential (link) but I'm not sure if it's adjustable.

I'm on my second freezer in 2 years and want to make sure that the differential is not set too small by mistake which would cause the compressor to cycle on/off too much killing it prematurely.

Thanks!



Kal


 
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Old 12-17-2009, 04:57 PM   #2
dwarven_stout
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I have no experience with that controller, but it's at least possible that it's adjustable. Pop the cover off- if you see these guys on the PCB, you can *probably* adjust the hysteresis:



As to whether or not it's recommended to fiddle with knobs under the hood of that thing... well. If you have a multimeter and a basic knowledge of circuits, you're probably ok fiddling. If not, I'd settle for the 3.5 degree setting.
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Old 12-17-2009, 05:04 PM   #3
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Strike that last post.

I dug up the technical doc on that controller. Looks like the unit is completely self-contained inside the cover, and it looks like you're stuck with whatever hysteresis they set. I'd still pop the cover off and take a look.

http://www.vikingcontrols.com/_docum...uct/125020.PDF
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Old 12-17-2009, 09:21 PM   #4
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Thanks for checking and finding the tech doc on it! Very useful. It's going in my brewing equipment binder.

I'd have no issues with the electronics but if the hysteresis is hard set to 3.5'F and there's no control to adjust it (or more importantly instructions on how to set to 3.5'F) I'll leave it alone. Thanks!

Kal

 
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