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Thread: Looking for wiring advice for WiFi thermostats

  1. #1
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    Looking for wiring advice for WiFi thermostats

    I'm considering 3 Ecobee Lite's for my 3 zone system. I only have 2 wires at each thermostat, so I need to get a C-wire or equivalent to each.

    Some years ago I replaced the original mercury thermostats with programmable ones.

    A picture of the inside of one is here (2 wires with a jumper connecting RH and RC):

    Click image for larger version. 

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    At the boiler (heat only - oil), I have 3 Honeywell zone valves with thermostat wires connected to the top of them - picture here:

    Click image for larger version. 

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    The connections (5) on top of them are labeled: END, SWITCH, TH/TR, TH and TR - picture here:

    Click image for larger version. 

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    The wires all seem to go up to a transformer on the ceiling above the boiler, pictured here:

    Click image for larger version. 

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    I need to add a C-wire to my system, and supposedly a FAST-STAT Common Maker will substitute for that.

    Here's my question - Can I make those WiFi thermostats work with a FAST-STAT Common Maker? The reason I'm asking is I could not find a wiring diagram with the FAST-STAT Common Maker that looked like my system. If I can, where do I connect the FAST-STAT on the boiler end. (I can see where it connects on the stat end.)

    Link to FAST-STAT Common Maker: https://www.fast-stat.com/

    FAST-STAT Common Maker suggested wiring diagrams:

    https://www.fast-stat.com/wp-content...mmon-Maker.pdf

    https://www.fast-stat.com/wp-content...g-Diagrams.pdf

  2. #2
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    It seems every boiler installation is unique. You will need to trace wires to find out which ones go to the thermostat and which to the transformer. Strange that you have one wire on the TH/TR screw as that is normally empty or has two wires on it. Again normal case would match the diagram with TH/TR being R, TH being W, and TR being C. But it might not be so tracing wires is needed. Sometimes each valve is different so need to review everything. Look at figure 14 and see how close your system is: https://forwardthinking.honeywellhom.../95c_10932.pdf

    Might be easier for you to talk with your boiler tech to get them to install.

  3. #3
    Junior Member

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    Thank you for your reply. I'll take a close look in the morning and post back. I'll look to see if it's like Fig 14, except for only 3 zones.

  4. #4
    Junior Member

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    Quote Originally Posted by Stuff View Post
    It seems every boiler installation is unique. You will need to trace wires to find out which ones go to the thermostat and which to the transformer. Strange that you have one wire on the TH/TR screw as that is normally empty or has two wires on it. Again normal case would match the diagram with TH/TR being R, TH being W, and TR being C. But it might not be so tracing wires is needed. Sometimes each valve is different so need to review everything. Look at figure 14 and see how close your system is: https://forwardthinking.honeywellhom.../95c_10932.pdf

    Might be easier for you to talk with your boiler tech to get them to install.
    Yes - my 3 stats are wired like the first 3 are in figure 14. I don't have zones 4 and 5 like figure 14 does, but the rest of my stuff is wired like that.


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