Author Topic: Johnson analog temp control  (Read 529 times)

Offline bengelbrau

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Johnson analog temp control
« on: November 30, 2014, 07:29:13 PM »
I have a Johnson analog temp controller which has been supplanted in the refrigerators by a couple of Rancos. I would like to convert the Johnson to work with a heating pad, so I can ferment in the garage in winter. Anyone have an idea how to do this?

Offline Stevie

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Re: Johnson analog temp control
« Reply #1 on: November 30, 2014, 07:37:36 PM »
Could be wrong, but i am confident it is for cooling only.

Offline mabrungard

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Re: Johnson analog temp control
« Reply #2 on: November 30, 2014, 08:03:10 PM »
For the digital version, there is a jumper that is switched to change between heating and cooling modes. I'm almost positive that the analog version is the same.
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Offline Stevie

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Re: Johnson analog temp control
« Reply #3 on: November 30, 2014, 08:34:13 PM »
I went ahead and opened a spare that I had lying around. Nothing inside tells me it can be switched. Photos below.




Offline youngdh

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Re: Johnson analog temp control
« Reply #4 on: December 01, 2014, 12:49:52 PM »
I went ahead and opened a spare that I had lying around. Nothing inside tells me it can be switched. Photos below.





Based on your photos you would be correct. You have an SPST relay whose contacts close on temp rise above set point. Johnson Controls does make an analog SPDT relay (I have one) with 3 terminal screws. Bottom screw is relay pole, middle screw is to control a heating element and top screw controls a cooling element.

Offline bengelbrau

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Re: Johnson analog temp control
« Reply #5 on: December 01, 2014, 03:07:15 PM »
Thanks, everyone.

Offline a10t2

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Re: Johnson analog temp control
« Reply #6 on: December 01, 2014, 04:59:50 PM »
If the model number ends with "C" or "F", it's SPDT.

http://cgproducts.johnsoncontrols.com/MET_PDF/125020.PDF
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