A German-made heat and refrig. system outboard of a large 6-color sheet-fed
press controls the temp of the h20/glycol coolant circulated in the press.
The PLC that controls all this has gone brain-dead and is quoted at ~10K to
replace. Owner simply wants cooling function (it's N. California, so no sub-0
temps to worry about) and the simpler the better. A simple thermostat with
remote sensor would do the job.
Contactors for compressor & fans are standard 24vac or 120vac stuff. Refrig
circuit has lo- and hi-press switches which can be incorporated to shut
everything down if need be. Coolant (glycol) circuit has flow sensor switch
so to protect pumps if level goes to zero. All this "safety" stuff can be
incorporated with little trouble.
Regarding temp control, I've looked in Grainger's catalog but everything I
see is ambient air type thermostat or remote-bulb type sensor. Are there
controllers that use electrical (ie, 2-wire) sensors that can be bolted in
place of the existing ones in the coolant plumbing (the existing ones are of
unknown origin and will probably be incompatible with any aftermarket
Any suggestions helping me find a thermostatic controller for this
application would be greatly appreciated.