Connecting a separate heat and cooling T-Stat to a single Ecobee 3


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Old 01-29-19, 08:25 AM
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Exclamation Connecting a separate heat and cooling T-Stat to a single Ecobee 3

Hey Everyone,

I was gifted the Ecobee 3 WiFi T-Stat. I currently have 2 separate thermostats, one to control cooling via central air and one to control heating from a natural gas boiler. Can I combine these two separate systems to work off of one Ecobee T-Stat?

(the round T-Stat) is used to control the central air and has the following wires:
Green wire to G
White wire to Y
Red wire to R
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(the rectangular T-Stat) is used to control the heat and has the following wires:
White wire to W/AUX
Red wire to R and jumped to RC.
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Please let me know if im missing any vital info, thank you in advance for reading and any assistance.
 

Last edited by PJmax; 01-29-19 at 10:21 AM. Reason: resized pictures
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Old 01-29-19, 09:21 AM
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Should work fine but you will need the PEK module that comes with the Ecobee 3. Three wires from the a/c need to attach to PEK at air handler leaving the W unconnected at both ends. Then use the boiler's W and R to W1 and Rh on the Ecobee.
Start with the boiler diagram: https://support.ecobee.com/hc/en-us/...iring-Diagrams

https://support.ecobee.com/hc/en-us/...Kit-no-C-wire-

Note Ecobee 3 is different from the Ecobee 3 Lite which doesn't support your config. If you have the newer one you can't use the PEK and instead need something like a Venstar add-a-wire.
 

Last edited by Astuff; 01-29-19 at 09:43 AM.
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Old 01-29-19, 09:48 AM
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Thanks for the fast response, I will try it that way hopefully tonight. I appreciate your input.
 
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Old 01-29-19, 10:15 AM
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Welcome to the forums.

Title changed to Ecobee 3.
 

Last edited by PJmax; 01-29-19 at 04:16 PM.
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Old 01-29-19, 10:30 AM
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Which thermostat do you have? Title of this tread is Ecobee 4 but you mentioned Ecobee 3? And the 3 is older which is different from the 3 Lite.
Ideally you would have an extra wire going to the air handler that could be used for C.
 
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Old 01-29-19, 01:57 PM
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Whoops!

Sorry for the confusion guys. It is definitely the Ecobee 3 (not lite).
 
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Old 01-11-20, 08:01 AM
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Google Nest thermostat

Hey guys, with the help you provided we were able to get this working. Side question:

would this same wiring setup work for the Nest thermostat? It's have more features/capabilities and we'd like to make sure it works before we get it.

any advice would be appreciated.
 
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Old 01-11-20, 01:03 PM
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It may have more features but the Ecobee is a better thermostat. Definitely more reliable.

The nest should work as you won't have a C connection.
 
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Old 01-13-20, 07:39 AM
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"It may have more features but the Ecobee is a better thermostat. Definitely more reliable.

The nest should work as you won't have a C connection."

Thanks for the advice Pete.
 
 

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