Wiring thermostat to boiler

stratsg

Oil fired boiler
2 zones

2 thermostats but one is not wired to boiler. Looking for correct way to wire the 2nd thermostat.
In pic there is a red/white wire from zone valves to transformer (?) and red/white wire of first thermostat with reds connected to each other and whites to trans former.
Also a single red wire running from zone valve to transformer.
In picture you can also see the  unwired second thermostat wire.
My question would be where to attach the red and white wires of the second thermostat?

stratsg

Also feel free to correct any of my incorrect terminology. Carpentry is more my thing.

Alan (California Radiant) Forbes

There’s a diagram of how to wire them right on the zone valves in your photo. 

stratsg

Guess I'll have to find my glasses so I can actually read that. Thanks

stratsg

Any chance I can get  more of a "put the white wire here/ put the red wire there" answer?  I'm trying to get heat to my mom's bedroom for the night.

Jamie Hall

Not really... problem is, electricity is colourblind, and one has to know what the wires are connected to -- and what they do -- rather than just going by colour.

EdTheHeaterMan

You can always just manually open the zone valve to get the heat to flow to the problem zone.

Here is the wiring diagram from the valve manufacturer, As @Jamie Hall said, electric is colorblind but this diagram has some a helpful hints where the R terminal from the transformer MUST go to the R terminal of the thermostat.
The W terminal for the thermostat MUST go to the 1 terminal of the zone valve.
The C terminal of the transformer must go the the 2 terminal of the zone valve
Finally the #3 and the #2 terminal will operate the boiler control

Important to be sure to wire all the zones the same. if you mix up the thermostat or transformer wires from one valve to another, you could burn out the transformer on the boiler control. I have had many professionals come to me with incorrect wiring of zone valves that cause the transformer to fail. And the transformer that fails is never the easy one to replace. It is always the transformer on the expensive boiler control that fails. and that one is not replaceable. You need to purchase the entire new expensive boiler control.

EDIT: From the out of focus photo it appear that the wiring is not exactly as the manufacturer diagram indicates. I have seen where another wiring design will work, but when there is a problem (like you are experiencing) it becomes difficult to determine where the problem is. Also it appears that the #2 and #3 terminals ARE connected to each other via a jumper wire and therefore both are connected to the boiler control. Perhaps you have a defective valve actuator. This is common and one of the reason there is a manual lever on the valve to offer a way to heat the zone until a replacement part can be purchased.

Mr.Ed

Zman

You can manually open the valve just to get the heat going.

stratsg

Zman said:

You can manually open the valve just to get the heat going.

Yep. That's what I did for temporary fix but I would like to be able to control that zone separately in the long run.

Zman

Those 3 wire Taco zone valves are a little complicated to wire. I would suggest upgrading to a zone controller and wiring it per the instructions. https://www.supplyhouse.com/Taco-ZVC403-4-3-Zone-Valve-Control-Module-with-Priority

Jamie Hall

Zman said:

Those 3 wire Taco zone valves are a little complicated to wire. I would suggest upgrading to a zone controller and wiring it per the instructions. https://www.supplyhouse.com/Taco-ZVC403-4-3-Zone-Valve-Control-Module-with-Priority

Not really... I did find them confusing at first, but once you get used to the idea that that middle contact is used for two different circuits it's not too bad... if slightly wacky.