I have a two-zone gas hot air and air conditioning furnace. Main level thermostat controls mail level, upstairs tstat controls upstairs.

Main control panel on the furnace takes in wires from both thermostats:
Zone 1:
G, B, O, Y, W, and R

Zone 2:
R, Y, W

Zone 1 controls heating/cooling function of Zone 2. Zone 2 only controls whether to turn on or off based on temp setting.

I purchased two new Honeywell theromostats: RTH7600d and RTH6400d. The 6400d for zone two should be straightforward (R to R, Y to Y, W to W) - and I should just have to ignore the fan auto/on setting.

However, my issue is with the zone 1 tstat. I can't go 1:1 with the wiring, and honeywell told me that this tstat would work although I can't get them to respond to email or phone.

Can anyone help?

Thanks!

While the models you have listed are NOT listed to use with the Trol-A-Temp system if that is what you have they might be able to be made to work. You did not post which zone system you hae as far a model numbers are concerned so I could not look them all up. Who at Honeywell said they would work? Or did some salesman tell you they would work?

Quote:

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Originally Posted by hvac1000

While the models you have listed are NOT listed to use with the Trol-A-Temp system if that is what you have they might be able to be made to work. You did not post which zone system you hae as far a model numbers are concerned so I could not look them all up. Who at Honeywell said they would work? Or did some salesman tell you they would work?

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Hi! Carrier conventional gas forced hot air with A/C. No heat pump.

The control panel is an EWC ultrazone ewc-st-2d, pic attached. I am not worried about the 2nd zone control as the call for heat/cool *should be* fine with the smaller new honeywell.

The zone 2 tstat is wired R to R, W to W, Y to Y.

The zone 1 tstat is W to W, Y to Y, R to R, O to O, B to B, G to G.

Everything makes sense to me (G fan, etc) except the O and B.

On the other side of the panel, connecting the control board to the furnace, R is R and B is common. G to G, W to W, y to Y. O not used. My thoughts in looking at it now in-depth (and not before when I asked the question) is that if I wire the 7600d R to R, W to W, G to G, Y to Y, O to O and B to Common, ensure the setting on the honeywell is 170: 1 (heat/cool), 190 to 0, I may be all set?

The one thing I didn't do last night when I reverted back to old was to trace from the board to the furnace itself...

Let me know your thoughts? Greatly appreciate the help!

http://www.ewccontrols.com/acrobat/090377a0055.pdf

Main site for more info

EWC Controls


YOU might read this since it does call for different part number Honeywell stats.

http://www.ewccontrols.com/acrobat/090375a0115.pdf

Sometimes have the right reference material can help. I believe you are headed in the correct direction..

Thanks for the links! I couldn't find it earlier.

OK here's where I'm at. I've successfully replaced the zone2 tstat with the new 6400.

Works fine if I leave the old Robertshaw 9610 in place. Cannot get the 7600 touchscreen to work - darn O and B wires - so I'll need to take it back and I guess find a professional grade one from a honeywell rep.

If anyone has any ideas let me know otherwise thanks for all of the help!

Just wanted to close the loop on this thread; there are only 4 models of tstats that work with my control board, and they are in the EWC page mentioned above.

I did speak with John at EWC and he informed me that there is one new tstat (the White-Rodgers 1f95-1271) that works with my panel.

FYI for anyone out there in a similar scenario.

All the best, and thanks again for all of your help! Was very helpful, and much appreciated!