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Phil, Mechanical Engineer
Category: Electrical
Satisfied Customers: 8511
Experience:  Retired electrical contractor, 51 years experience.
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I installed 3 nest thermostats about 5-6 months ago, and I

Customer Question

I installed 3 nest thermostats about 5-6 months ago, and I am not finding that I have relay chatter at my boiler. I have since looked online and found that this seems to be a relatively common issue and that the 2 wire setup of the nest can cause this with relays. A solution seems to be adding a C common wire to the setup. I have a third wire running from the thermostat setup in at least two of the locations but I have not idea A. which of the wires at the boiler end corresponds with the wire at the thermostat end and B. where to connect it at the boiler end once I know which on it is.
Submitted: 1 year ago.
Category: Electrical
Expert:  Phil replied 1 year ago.


There needs to be a common wire connected to C on the thermostat, tell me if your Nest models have that C terminal or not, do not wire it yet. I still need more data, but we can begin there.

Customer: replied 1 year ago.
There is no wire connected to C on the thermostat yet but there is an available 3rd wire. There are two 2 wire pairs running from at least one of the thermostat locations to the boiler room. One problem is that one the other wire pair, I'm not sure which wire is which at each end and not sure I have a tester handy.
Expert:  Phil replied 1 year ago.

Hello again, there are several dozen different wiring configurations, we need to work from wiring diagrams. verbally so to speak will not work. It can be a bit more complicated than you might imagine,

If you can make a pencil drawing of the three thermostats showing how they are all wired and what each controls, of if all 3 go to a zone control box, and a the brand and model of the zone control box, that will help immensely.

Customer: replied 1 year ago.
Thanks. I realize now that this is a little over my head. Thank you for the assistance!
Expert:  Phil replied 1 year ago.

You are welcome

Thanks for letting me work with you. When we are finished,if my answer has been polite, professional, and thorough, please locate the 'rate your expert button' and click one of the ratings .

If you still need help let me know!. Rating will not increase your charges, nor close the question, but is how I earn my living.

Expert:  Phil replied 1 year ago.

I will be back in the morning if you want to send me a drawing etc, we can go from there in that case.

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