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MC80 Contender Second Heating Zone wiring using built-in DHW: Questions

bergmanjbergmanj Member Posts: 2

I have been using an MC 80 Contender a number of years now for radiant in-floor heating a finished basement walk-out concrete slab operating at 120*F max. We have just finished our upstairs of this retirement home of ours.

I want to use the DHW sensor inputs and DHW circulator pump outputs (to a 2nd, separate pump) to supply the 4-zone-valve system for the newly installed upstairs radiation (properly sized for use of 'Smith's Environmental HE-3' emitters - at the same 120*F loop supply temperature).

The in-use t-stat input is simply a contact closure, upon heating call, across open-circuit 24VAC at "Low Voltage" terminals 7 & 8; and, works well.

The proposed-to-use DHW inputs (at terminals 6 & 7, also in the "low voltage" side) are +5VDC at terminal 7 with respect to return at terminal 6. What current (I assume, in milliAmps) does this circuit supply/able to handle; maximum?

After much research, I have not been able to tell whether these DHW sensor inputs are intended for a contact closure, thermistor (what value & type - 10K @ 0*C NTC, 100K - PTC, etc., for instance) RTD (again, spec's?) or other input type; is anyone here able to answer these questions with very specific data/specifications?

I'll appreciate any/all helpful answers.

Regards, JLB


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