Combining Thermostats - Wiring Help

rumrunner9September 17, 2013

I'm trying to combine two old round style Honeywell thermostats into a new single Honeywell 7600D thermostat. One of the old thermostats controls the central forced air cooling, while the other old thermostat controls baseboard hydronic/boiler heat. All components are 24V. Each sheath has 3 wires only (R,G,W).

The heating system has 6 zones controlled by Honeywell V8043F1051 valves. I'm interested in only merging one of those zones with A/C into a single thermostat. The cooling is conventional compressor/air handler (no heat pump).

Current wiring is as follows:

Heat Thermostat to valves
R/RC --> red wire --> THTR
Y --> white wire --> not connected
W --> green wire --> TR

Cooling Thermostat to Compressor/Air handler
R/RC --> red wire--> switch/power
Y --> white wire --> cooling
G --> green wire --> fan

On the Honeywell 7600 thermostat can I connect as follows?
From heat:
red wire --> R
white wire --> leave unconnected
green wire --> W
From cooling:
red wire--> R
white wire --> Y
green wire --> G

In this case I'd be combining R to the same post which I'm assuming is not correct. Can I use the R from the cooling system to send current for heating (w) switch? Is there a way to wire these up to this or any other thermostat? Any guidance would be greatly appreciated.


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So would this thermostat wiring work?

From heat valve control wire:
red wire --> R (remove jumper)
white wire --> leave unconnected
green wire --> W
From cooling system wire:
red wire--> Rc (remove jumper)
white wire --> Y
green wire --> G

    Bookmark   September 17, 2013 at 8:39PM
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I assume you have separate transformers for heating and cooling systems. If that is the case then remove the jumper between the R and Rc terminals. Connect the red wire for heating to R and the red wire for cooling to Rc.

I think the rest of the wiring will work as long as you don't mix your similar color wires. You also have to program the thermostat for the correct heating and cooling system.

    Bookmark   September 17, 2013 at 9:01PM
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Isn't that what rumrunner9 said? ;-)

    Bookmark   September 17, 2013 at 9:32PM
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You are right. I didn't read his second post carefully.

At least we are in agreement.

    Bookmark   September 17, 2013 at 11:05PM
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