Help with Nest Thermostat shutting off in cold weather

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Old 01-09-18, 04:36 PM
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Help with Nest Thermostat shutting off in cold weather

Have a Nest Thermostat hooked up to my upstairs zone from my boiler. Downstairs zone has old Honeywell thermostat. Nest Thermostat has been hooked up for about 1 yr and now noticed during very cold days for a long period of time it loses power or not enough to charge Nest. Nest is hooked up to my AC unit in the attic too. I have a two wires coming from boiler and 5 wire coming from attic AC unit. The two boiler wires are hooked up to W1 and RH and AC 3 of the 5 are hooked up to Y1, G & RC on the Nest back plate. Nest power was not working for the past 2 days since Attic temp went to 5 t o minus 4 here is NJ. Once it got above 25 degrees today the unit started to charge an come on. I called AJ Perri Service and tech indicated I need a 24 volt isolated relay and wants to run a new set of wires to hook up to C on thermostat. When the Nest was not working I touched the wires and got a little shock so some power was still going but not enough or too much to make Nest Thermostat Charge. So have couple of questions:
1. Anyone ever hear of this when attic gets very very cold?
2. AJ Perri want $600 to do this work, is it easy to do? I have some handyman skills.
3. Also I connected my Honeywell from downstairs during no power and that did not turn on as well.

Any help would be appreciated.
 
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Old 01-09-18, 05:36 PM
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Welcome to the forums fellow Jersian.

I don't think it was due to a cold attic as much as the heat was running more and not allowing the nest to charge properly. A very common problem.

The two boiler wires are hooked up to W1 and RH - That is correct.
A/C 3 of the 5 are hooked up to Y1, G & RC - That is correct.

Now you need to take one of the extra wires from the stat to the A/C and make it a C wire.
Go up to the attic and locate where the thermostat cable connects. It could be a terminal board or with wire nuts. Take and post a few pictures of the wiring and we can direct you what to do.
How-to-insert-pictures

 
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Old 01-15-18, 01:56 PM
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Thanks! I will try and take pictures of the wiring on the AC up in the attic. A representative from Nest also told me to disconnect the 3 AC wires in the winter and just use the two wires from the boiler.
 
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