Another Nest Power Adapter Mess


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Old 10-04-22, 01:29 PM
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Another Nest Power Adapter Mess

Hi,
I am trying to hook up two Nest thermostat's to my heating only system. I had the low power C wire needed and purchased two Nest Power Adapters. I have been unsuccessful at getting everything working. I have been able to get the Power Adapter detected by the Nest, but when calling for heat the circulator triggers, but the Taco zone valve isn't opening.

I have tried many different configurations, but nothing has worked yet.
The Hydrostat has Red and White sent from TT connections to the Zone valves. There is also a 24v Transformer that I tried using with the Nest power Adapter. I tried with and without the power adapter jumper removed.
The white wire from TT runs across the three Zone valve #3 terminals, the red TT runs across the #2 terminals. There are 3 zone valves, but one isn't active, it must be for adding a zone if needed in the future.

Any help is greatly appreciated.




 

Last edited by PJmax; 10-04-22 at 05:43 PM. Reason: resized/labeled pics
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Old 10-04-22, 03:09 PM
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1 - It is strange to have an unused valve, especially when there is wiring going to it. Are you sure that you don't have a third heating zone or for a hot water supply?
2 - You don't need to touch the Hydrostat.
3 - The 24vac transformer needs to connect to the white C and R wires on the Nest Power connector. One wire from the transformer should connect to the middle #2 screw on the zone valves. This is C. The other wire from the transformer should be spliced to feed the two (three?) thermostat feeds. This is R. Then the white W/Y on the Nest goes to screw #1 on the zone valve. Then the grey wires on the Nest feed the thermostat.
 
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Old 10-04-22, 05:03 PM
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Thanks Astuff ,
Yes, I found the terminated valve odd myself. New home for me, so I never looked into it much. I will pull the wires to make this a bit easier. Pic at the bottom.

I believe I had it set up as you pointed out when I had the thermostats working and the circulator pump going, but the valve was not opening. With C from the transformer going to the middle #2 screws. I will go and hook it up that way to be sure.

Do you know if the jumper on the Nest power adapter should be removed in this configuration? I had it removed based on the Nest advanced install guide.

 
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Old 10-04-22, 05:28 PM
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Capped off. You likely used to have another zone. No wire on #1 so no good clue but you may find some abandoned thermostat wires somewhere else in the house.

The Nest jumper should be installed as yours is a standard installation..

Here is a good diagram showing connection labels in the second post: Wiring a three wire zone thermostat
 
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Old 10-04-22, 05:36 PM
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Huge thanks to Astuff !!

Your wiring info was correct. That was definitely not how I had it when I had the circulator pump going. I am all set; up and running now.

Oh... Jumper in the Power Adapter was needed as well.
 
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Old 10-04-22, 05:40 PM
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I would disconnect the unused valve.
I illustrated the wiring starting over.
That would be the easiest way to go.

There is no polarity on the TT wires at the boiler or on the W and R thermostat lines.
 
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Old 10-04-22, 05:54 PM
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Thanks PJmax & Astuff everything is in order now.
 
 

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