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t-stat wiring issues

Bob Forand
Bob Forand Member Posts: 305
Well after pulling a few more hairs out, and a little help from Peter at Emerson Swan, we figured it out. There IS polarity when hooking up thermostats. Apparently red goes to the right, white to the left. The "B" wire I was talking about was blue. Pulled common from 24V block on the SR back to common on stat and changed a few wires around and all is well....


  • Bob Forand
    Bob Forand Member Posts: 305
    Need help with tstat wiring

    I need some help with wiring on a Fast Stat TS21. Where do I pull common from to power the stat ? I have a couple of issues going on and I cannot figure out what is happening. First, simple basic, hydronic heat zone. Tstat is on-off only, Three wires R,W,and B, connected at stat and then run back to Taco SR. Tried pulling common from block on SR control and the pump stays powered regardless of stat. Thinking that polarity, or common is the issue, I then tried to pull common from Unico wiring block and there was no change. The pump is still powered regardless of stat. I have the same problem with a second TS21 stat set up as 2 stage. First stage baseboard, and second stage is Unico. When the stat is wired as single satge Unico, everything works fine. When I move W2 to OBW on stat and then hook up W2 and run back to SR control the same issus happens, pump is energized, regardless of stat. That is why I think that is has something to do with the common. Any ideas ???
  • Diagram...

    Got a link to or a pic of the wiring diagram for the stat?
  • Empire_2
    Empire_2 Member Posts: 2,343
    Hey Bob?

    Yes a- Little help as in diagrams or something you scetched would help.
  • lee_7
    lee_7 Member Posts: 458

    do you have any type of isolation protection between the two 24v circuits, one from sr control and pother from unico?
  • Right,

    B terminal is not normally a common so I question why you're hooking it anywhere. B normally energizes on a call for heat.
  • Darryl_3
    Darryl_3 Member Posts: 6
    Replacing Steam Vents

    Looking to replace main steam vents on a residential system.

    Do they need to be sized or can it be an exact replacement of existing size vents?

    Also, the radiators are different sizes. What would be the best approach in determining proper radiator vents as well.

    Are adjustable vents better than fixed?

    Any info and suggestions would be appreciated.
  • lee_7
    lee_7 Member Posts: 458

    start new thread for better response to your different question
This discussion has been closed.