Is this a viable option for c wires to smart thermostats controlling a hydronic Boiler

zvalve

I have two Honeywell 4 wire zone valves on a heat only hydronic system and can this wiring diagram and common maker be used to add a c wire for smart thermostats? Diagram M

Jamie Hall

Well... the company appears to make the claim that it can, so who am I to argue? Not sure what the question is.

I will say that some considerable care should be taken in clearly identifying which wires do what. Do NOT depend on the colour code on the existing wires. I imagine that miswiring something could fry it pretty easily.

HomerJSmith

I think it looks good.

EdTheHeaterMan

Jamie Hall said:

Well... the company appears to make the claim that it can, so who am I to argue? Not sure what the question is.

I will say that some considerable care should be taken in clearly identifying which wires do what. Do NOT depend on the colour code on the existing wires. I imagine that miswiring something could fry it pretty easily.

Agree with Jamie on this. I have been tech support for a local supply company for a few years during my career in HVAC. In that position i have found that many plumbers that were excellent craftsman have problems with control wiring. Especially when zone valves are concerned. This is because there are more than one way to wire a zone valve correctly. The problem comes when a Professional gets used to doing things a certain way, then they come across a job where someone else prefers a different way. If the two different wiring ideas or designs are mixed and matched on the same transformer, that is when the smoke comes out of a transformer. And we all know if there is more than one transformer on a system, the smoke will come out of the one on the most expensive control in the system.

I have always preached that matching the letters will always make for easy to understand wiring. R on the transformer connects to R on the thermostat. C on the transformer connects to C on the thermostat and C on the operating control (in your zone valve one of the yellow wires), and W on the thermostat is always the wire to the operating control. (in your zone valve that would be the other yellow wire).

So make sure the wires are actually connected to the proper terminal at the opposite ends of the wire(s)

HomerJSmith

If you have 3 wires (R_W_G) at the thermostat to the boiler, why are you doing this Fast-Stat sys?

If you want help in wiring a Nest to your boiler, answer my questions on your other post.

zvalve

Ok Homer thanks