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Adding C wire with boiler with taco zone valves

Cks
Community Member

I have an older boiler that uses Taco Zone valves. I am trying to add a Nest 2020 thermostat and I do not have C wire. I bought an adapter to add 24 V for the power. The wire exiting the the old thermostat goes to the zone valve and completes the loop to energize the valve to open when there is a call for heat. The Taco valve works off it’s on 24 V transformer. If I add a thermostat add on 24 V C wire ( one wire to the C and one to the R) I would think the zone valve would stay open. Can power be added to this and how?

5 REPLIES 5

Houptee
Silver Product Expert
Silver Product Expert

Does your Nest have both Rh and Rc terminals or only R?

If you have Rh you put Red there and White to W1 and then the AC transformer wires go to C and Rc

If you only have R on the Nest then you combine your Red wire with one wire from the Ac adapter and other wire goes to C

Here is a video that should help

https://www.youtube.com/watch?v=yi5kfn3bmEk&ab_channel=OneHourSmartHome


Houptee -- NJ Master HVAC Licensed Contractor

Patrick_Caezza
Platinum Product Expert
Platinum Product Expert

The thermostat terminals on a Taco Valve Controller typically are looking for a switch closure (like a light switch).

You'll need an external 24Vac transformer and the Google Nest Power Connector.

This is an example of how it could be wired.

2022-04-06_182952.jpg2022-03-01_173137.jpg


To ensure that I see your reply, please tag me using @Patrick_Caezza

EdwardT
Community Specialist
Community Specialist

Hi folks,

 

@Houptee and Patrick_Caezza, thanks for the help!

 

@Cks, how's it going with your Nest Thermostat? Still need our help?

 

Thanks,

Edward

Jeff
Community Specialist
Community Specialist

Hey Cks,

I just wanted to follow up once more to see if you were still needing some help here. If so, just let us know.

Thanks,
Jeff

Jeff
Community Specialist
Community Specialist

Hi everyone,

Just one quick final check in here since activity has slowed down. We'll be locking the thread in the next 24 hours, but if you still need help, I would be happy to keep it open. If there's more we can do, just let me know.

Thanks,
Jeff