temperature controller, which model?

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balto charlie

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Hey folks: I need a temp controller for my fermentation chamber. I know most folks buy the Johnson A419 which controls heating or cooling. I have that on my keezer. I only need the controller to heat so do I need one where the SPST opens high with a range of 30-100F? These are much cheaper $20.00 vs. $50.00 for the models that heat and cool. The model I am currently looking at is A19AAB. Thanks for any info. Charlie
 
Just an AM bump

I guess the main question I need answered is "What does open high" mean?
Thanks Charlie

Thanks Wild just trying to shave off a few $$
 
Just an AM bump

I guess the main question I need answered is "What does open high" mean?
Thanks Charlie

Thanks Wild just trying to shave off a few $$

You have a remote bulb, analog Johnson controller with a fixed standard differential and configured to "open high" which I interpret to mean that the circuit will open as the temperature rises and reaches the set point. IIRC, this configuration is for heating only. For cooling, you would want the compressor to turn on with a rise, not off. However, you may luck out and have a unit with a double throw internal switch. To find out, remove the cover and look at the switch which is directly below the adjustment dial. There should be three terminals, but the unused one may be concealed by a small plastic plug. Look for this plug either in the center or the top of the switch. In you case I would expect the top terminal to be plugged and the middle terminal connected to a lead. The "open high' can be switched to "open low" by moving the lead from the center terminal to the top terminal. Now then, looking at manual specs for that unit, the switch may be a SPST type with only two terminals. If that's the case, you won't have any way to reverse the cut-in/cut-out and you will be stuck with "open high" (heating mode).

If your switch looks like the one in the manual pic you can hack it as described above:

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