Programmable Thermostat wiring question -rth7500

Jan 01, 2005 3 Replies
T

Happy New Year!



I'd like to ask for help with my Honewell RTH7500 thermostat.



I am replacing a White-Rogers 1F35-910 thermostat in my house. The RTH7500 was suggested by Honeywell support. I have a gas boiler system for heat.



The wiring on the white-rogers is to terminals R5, Y6 and 4. None of the literature that I could find on the RTH7500 has these terminals...they're either R, rc, rh, or y and y1...but no R5 and Y6. I cannot find an association for the "4" either.



The informational page on the white-rogers can be found here:

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I tried searching the Honeywell site, but the online wiring assistance doesn't include the newer models and when I called, their tech support for homeowners is only available M-F 8-5?!



Can someone describe the wiring correlation between the WR model and the rth7500?



Thank you, Dave



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T

HNY to you, too.

The 1F35-910 is an SPDT thermostat used for 3-wire Zone Valve Heat Only applications.

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page 1

The Honeywell stat should work fine.

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page 18

4 = Call for Heat = W 5 = Hot side of transformer (power) = R 6 = Thermostat satisfied = Y

Don't forget to configure installer setting 0170 for the 3-wire zoned hot water application.

Hope this helps.

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T

I noticed that too, Dave. All I can conclude is that some thermostat manufacturer out there must use the 4 terminal to designate the transformer hot side. By looking at the WR schematic you'll see that on your thermostat terminal 4 is used to actuate the heat valve (the W terminal).

Wire it up and let us know how it works.

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T

Glad to hear all is OK, Dave.

I can't see your thermostat from here, but on the WR instruction sheet the terminals are just labeled 4, 5, and 6. So let's assume your WR thermostat labels mean "Y" and "6".

The "Y" terminal is classically used to enable the compressor (cooling) circuit. In the case of the Honeywell thermostat it is also the 'call for heat satisfied' side of the SPDT relay, which is why it works in your application.

Travis

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