Does this support the same wiring configurations as the Nest 3rd gen? I live in an apartment and cannot run extra wiring for the HVAC system. null

Question

dorkhead2 · Accepted Answer

No. The Nest is designed to run with or without a C-wire. The Honeywell thermostat (Model: RTH9585WF) is designed to use the C-wire or an alternative installation using the G-wire, if the C-wire is not present. So the two thermostat's wire configurations are not necessarily the same, but depending on your situation, you may be able to use this thermostat if all you're missing is the C-wire, but you have a G-wire to use in its place. The G-wire normally controls the operation of the system’s fan, but if it's used as a substitute for the C-wire, then the fan can no longer be used independently. What this means is that the fan will only turn on/off when the air conditioning or heater is running. If you never run the fan independently, then this won’t be a problem. If you would like to maintain that functionality, then an electrician will need to install a C-wire on your system. Honeywell’s website provides a lot of information and videos regarding this and other installation topics. Good luck!

Answered by dorkhead2 8 years ago

Top 250 Contributor

Mike · Answer

Yes, it does. I would double check the compatibility on Honeywell's website but I went from Nest to this as well (in an apartment too) and it was a smooth transition.
My system has Central air, forced air gas furnace, and a central fan (4 wires with the ground, looks identical to your picture).

bmurtari · Answer

This thermostat will not work with the wiring in your picture. There is no common wire which is a requirement for this thermostat.

RangeExtended · Answer

No, it needs 5 wires

Webzpinner · Answer

Long as you have the C wire, you are fine with the rest. It’s a standard,

Saitzev · Answer

Hey Andyj, For this unit you may need to run additional wiring. If there is already a C-Wire (Common) in place you should be able to use this one. If not, then you would need to use the included C-Wire cable that can be configured to go from the G to C terminal at the Control Board.

From your picture though, it does look like you don't have the Common, so if it was working with the Nest, it might in fact work with your setup. Of course that does assume that the G-Wire you have there has been setup like I mentioned with the Cable like what is included with the Honeywell.

JackM · Answer

I believe C-wire is required.

cinsteadofak · Answer

Yes this unit uses the same wire configuration as the Nest 3rd gen. Since I only have one zone/stage and use forced air for heating and cooling, all I needed to use was the Y, G, W, C, and R spots. The ports on the back of the Nest 3rd gen look identical to this unit, but in a circle formation.

Answered by cinsteadofak 8 years ago

Top 1000 Contributor

MikeElectronicBuff · Answer

In short, Yes. But depending on how your Nest is setup most are 4-5 wire systems for Nest.

OrlandoDad · Answer

Yes it has the exact same wiring configuration. It does however require you to switch the mounting bracket.

“Does this support the same wiring configurations as the Nest 3rd gen? I live in an apartment and cannot run extra wiring for the HVAC system.”

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