Nest thermostat upgrade works intermittently in 1 year old in house


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Old 12-02-22, 09:11 AM
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Nest thermostat upgrade works intermittently in 1 year old in house

So I upgraded to Nest thermostat 2020's. My existing setup was a 2 wire setup (R&W only). I rewired everything numerous times at this point and cannot get theses things working reliably. On the most recent rewire I wired everything as the photo shows below.

Current Issues
-Downstairs Thermostat with not setup. App says does not detect C-wire.
-Upstairs I never hard reset due to wanting to make sure everything is working on at least 1 floor first. This thermostat is reading not power. If I do a power test it says VIN 45V. If we change the temp sometimes it'll call and other times it won't.

Current Equipment
-2 Nest Thermostat 2020's
-2 Taco 571-2 valves
-110-24v step down transformer
-1 Williamson Model 1135-601

Any help anyone could give would be amazing.




 
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Old 12-02-22, 02:54 PM
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On a Taco zone valve the #2 wire goes back to the transformer to complete the stat circuit and also 2 & 3 go to the burner.

XFORMER - #1STAT - #2 STAT - #1 ZV - #2 ZV - XFORMER COMPLETE SERIES CIRCUIT

#2 & #3 ZV - 2 WIRES ON BOILER TO START CYCLE.
 
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Old 12-02-22, 04:15 PM
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maybe Im not understanding what you wrote but it sounds like that's how i have it setup now. Can you clarify?
 
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Old 12-02-22, 04:19 PM
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Welcome to the forums.

Although a little vague your wiring is 100% correct.
When you rewire or change wiring to a nest you must reboot it or do a fresh start
so that it learns the new wiring.
 
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Old 12-02-22, 04:26 PM
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I just saw your boiler controller. Did you read its install manual ??

DO NOT connect directly from 3-wire zone valves to the T-T terminals on the boiler. When using 3-wire zone valves, install an isolation relay. Connect the zone valve end switch wires to the isolation relay coil. Connect the isolation relay contact across the boiler T-T terminals. Failure to comply can result in damage to boiler components or cause unreliable operation, resulting in severe property damage.
 
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Old 12-03-22, 02:45 PM
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The downstairs has been hard reset and still will not connect.

As far as the relay do you have an example of what I need? I'm Googling and getting to many different things.
 
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Old 12-03-22, 04:37 PM
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The relay is required if one or both stats says heating and the boiler doesn't respond or responds intermittently. The relay will have no effect on a thermostat not connecting.

You can use any 24vac single pole relay. Two are shown below.

 
 

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