Nest Showing No Power, Connected to Taco SR506

[MDA44]

Hello, I have a Nest Thermostat connected to a Heat Only gas boiler looking to run  common from my Taco 6-Zone SR506.  I have connected my Power and Heat, but the common still says not detected.  I have an extra wire at my thermostat that is also at my Taco board (Green coiled wire).  See photo of board, I currently have the unused green wire unattached, (but I tested it plugged into the 24V/Comm port) when it was unsuccessful I detached it to not cause any problems.  See last photo of app showing that it's not seeing that wire.  

When testing it, the Nest reads (What do these mean?  

VIN: 28.028V

lin: 30(w)

PS: W-30

What am I missing here?  Is using those the Taco for common not acceptable?  I was hoping to do this with (2) thermostats.  I have two other Nest in the house that are older versions and do not require commons and work with no problem with the boiler.  Any ideas would be great.  

FYI: I did test the Taco board with my tester and there is full power on the board.  I didnt pull the original wire but I dont think that would be the problem since the heat works.  

[CoolingWizard]

@MDA44 ,

Your C wire is not detected and your W wire is being used to reach the power common. The common is in the green terminal on the upper left side.  Attach the common wire to the common in that terminal black. 

AC Cooling Wizard

[MDA44]

Hello, thank you for the reply.  In the photo of the Taco you can see the coiled green wire at the top left.  That is the one that I had connected to the 24v comm terminal block right below it. I then connected that wire to the thermostat (it was there in the wall behind my old thermostat but unused).  Still no power.  I unattached it just for the time being to not cause any problems.  I don't know what those reading are that is on the Nest screen, can that help me diagnose?  Am I missing something? 

[CoolingWizard]

There are more than 1 green wires, are you sure you connected the correct one?

AC Cooling Wizard

[MDA44]

Yes, I actually tried to connect both (two different thermostats, same model) just two different Zones.  Theoretically should this board have any problem pulling common power from that block?  Have you seen it be successful?  If so, my only concern is there a splice in the line since that Green wasn't used at their one before.  

[CoolingWizard]

It is hard to determine.  What I do is turn the power off, then go to the zone controller and connect green wire the red wire.  Then go to the thermostat location and check for continuity between red wire and green wire. When you find the match, that will be the green wire to attach to common.  

AC Cooling Wizard

[Jenelyn_O]

Hi folks,

Thanks for posting in the Google Nest Community forum. I just want to check if you managed to see the response above. Please let us know if it works on your end as well.

I appreciate the input, @CoolingWizard.

Best,

Jenelyn