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Thermostat not turning on heat

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mc14
mc14 Member Posts: 1
in Radiant Heating
I have a 4 zone taco relay and taco circulators.  Hot water works and zone 2 works.  Zone three doesn't turn on.  Doesn't appear to register on relay light.  The thermostat worked for ac all summer and I spent alot of money trying to fix this last year and I thought it was fixed.  It never worked this fall except for a short time.  I can't afford the cost right now before holidays.  Got pictures of the system.  Any trouble shooting help would be much appreciated.  Thanks

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  • bburd
    bburd Member Posts: 917
    edited December 2022
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    Try, jumping the thermostat terminals for that zone at the relay box. If the zone indicator light and heat turn on, you either have a bad connection or broken wire in the thermostat circuit, or a bad thermostat.

    If the zone indicator light doesn’t turn on, the problem is in the relay box.

    If the zone indicator light turns on, but the heat does not, the problem is between the relay box and the circulator or zone valve.

    If you have zone valves, check the end switch connections.

    —
    Bburd
    MikeAmann
  • HomerJSmith
    HomerJSmith Member Posts: 2,441
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    Has this worked in the past and is now not working? What has changed prior to this problem? Do the four switches operate the pumps? Does zone three operate the garage?
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,852
    edited December 2022
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    to determine if the problem is in the Taco Control, place a jumper on R and W terminals on #3 zone where indicated.

    1. Turn the thermostat up to call for heat
    2. Touch the jumper wire to R and W on zone 3
    3. If the light for zone 3 lights and the relay clicks on, Then the problem is not the relay
    4. If the light does not come on then the relay is the defective part.
    5. The next step is based on the results of this test

    PS. I picked green for the jumper because it is already there in the upper right corner. Just cut off about 3" and peal back the insulation to make a jumper wire.
    Never Use The Parts Cannon.jpg

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • HVACNUT
    HVACNUT Member Posts: 5,841
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    If it is the Zone 3 relay thats bad, can you move everything to Zone 1? The low volt terminals are not used but the line volt side is used. What's up with that, future?
    You say the air conditioning works fine. The air conditioning operates off the Zone 3 thermostat? If the heat for that zone is an air handler with a hydro coil, it could be an isolation relay at the air handler or incorrect wiring. 

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