Adding C-wire to radiant system that uses 2-wire thermostats?

JLSF

Hi,



I've got a radiant hydronic heating system. I have 6 zones (thermostats). Each of the thermostats are really simple 2 wire-affairs --- one wire the RH and one wire to W.



All of the six thermostats go back to a Taco ZV406 zone valve controller (attached the schematic to this post) .... For each zone in the Taco, there are only two terminal connections (ostensibly one to RH and one to W)



So I want to upgrade my thermostats to fancy ones that require a third-wire --> common. I've determined that all my wires to my thermostats have an extra third unused wire.



So my question is --- to where on the Taco ZV406 do I connect the extra unused wire for which I would us as a Common wire to? I can't seem to figure it out...



Thanks

STEVEusaPA

one way...

First of all, your schematic didnt attach.

From the thermostat:

w goes on t

r goes on t

c goes to #1 on the Zone 1 block. #1, on the Zone 1 block is going to a 2-wire zone valve (no end switch). #2 on the Zone 1 block goes to the zone valve.  3&4 are jumpered.

Repeat for other zones.

http://www.taco-hvac.com/uploads/FileLibrary/100-9.0.pdf  start on page 51.



edit: Before you wire it up...what kind of thermostat? What kind of zone valves? What are you looking to do with the t-stat/3rd wire?