Replacing a Honeywell thermostat with B G Y O R W wiring by a Nest 3rd Gen

[Siamond]

I'm sure this is a rather common question, but I can't find a definite answer.

Possible, not possible? If possible, then how? There is a 'star O/B' connection on the nest, but this only takes a single wire. Help!

Honeywell thermostatNest thermostat

[Siamond]

I think I found the answer in an older thread:

<<[...] connect the wires the same as the old tstat but put red to RC, orange to O/B, and blue to C. then Y G W.

Tell it you have a heat pump system with forced air ductwork (i assume that is what you have).>>

And yes, I think (?!) I have a heat pump with forced air ducts. We bought the house a year now, can't say I'm familiar with everything...

Could somebody confirm this is what I should do? If yes, why is the Nest config tool telling me my "B G Y O R W" wiring isn't compatible?

[Patrick_Caezza]

Sound good to me

[Siamond]

Hm, actually, I'm having some doubts... "B" is an ambiguous label... I don't have a Blue wire, I have a Brown-ish wire... "C" means neutral, while Brown seems to be about 2nd stage heat (or backup heat)?

This being said, this wire is clearly labeled "B" on the Honeywell plate (see pic above).

[Siamond]

I climbed in my attic (we have a 2nd furnace up there, which is the one I'd like to control with the Nest thermostats). This furnace is single-stage (Goodman GMES96). I do not think there is a heat pump involved (there are two A/C units outdoors, we have A/C upstairs, controlled by the existing thermostats). I found a control panel on top of the furnace, but this doesn't really say the exact role of the "B" wire... Here is a picture. 

So far, I'm focused on the Zone 1 thermostat, but I'll do the Zone 2 thermostat shortly after.

[Siamond]

And I found the user manual of the Honeywell thermostat, with a more explicit functional diagram. Mine is a Honeywell Q539A1469 (see picture above). 

[Patrick_Caezza · Accepted solution]

The EWC Ulta-Zone Control System is not compatible with any of the Nest thermostats. 

This controller requires you to use a set type of thermostat.

[aatienza]

Hey Siamond,

I'd like to jump in here and check if you've seen Patrick_Caezza's response. Let us know if you need more help by replying to this thread.
 

Thanks,

Archie

[Siamond]

Yes, I did, and I recommended Patrick's answer. Tx.

[Jenelyn_O]

Hi there,

Thanks for the update @Siamond. It looks like we have come to a solution, so I'm going to lock this thread in 24 hours. If you have any other concerns or questions, please feel free to create a new thread.

Thanks @aatienza and @Patrick_Caezza for your help.

Best,

Jenelyn