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(Resolved) Air handler kicks on but Relay doesn't?

tommygags
tommygags Member Posts: 68
edited November 2022 in Thermostats and Controls
Hi everyone, having some heating issue. When the tstat turns on for heat, the air handler fan turns on but the relay doesn't click and no light on for that zone so the pump doesn't turn on. The same relay is powering another tstat and zone without any issues. I checked wiring and everything looks to be good. Fuses look to be good as well. 

Any thoughts on what I could try?

I have forced air heat with water coming from a tankless boiler. 

Edit: jumping RW on the relay turned on the circulation pump. 

Comments

  • Peakedtoosoon
    Peakedtoosoon Member Posts: 57
    Just to be clear, you have an air handling unit, with a hydronic heating coil. The fan starts, but the circulation pump for the coil doesn't......is that correct?
  • tommygags
    tommygags Member Posts: 68
    edited November 2022
    Yes, that is correct!
  • HVACNUT
    HVACNUT Member Posts: 4,856
    There should be an isolation relay at the air handler that the White wire from the thermostat connects to. The wires on the Normally Open contacts on that relay should go to R-W or T-T on the boiler relay. 
    Did you try to jump R-W on the boiler relay for that zone? Does the circulator run? If not, bad relay. If so, bad isolation relay or broken/faulty wiring.
    Are zone valves involved?
  • tommygags
    tommygags Member Posts: 68
    Thank you for this. I just jumped r and w and the pump turned on. Would I be able to test the isolation relay?
  • tommygags
    tommygags Member Posts: 68
    I did notice this blue wire not connected to anything
  • pecmsg
    pecmsg Member Posts: 3,532
    That blue wire is just a different speed.

    Using timers is a cheap way of controlling the fan until the coil gets hot enough.

    What's the wiring at the boiler look like?
  • tommygags
    tommygags Member Posts: 68
    edited November 2022
    Thanks for confirming that! Here is the relay, which is correctly working with my other zone. Zone 2 is the one that isn't clicking on, zone 3 is working correctly 
  • tommygags
    tommygags Member Posts: 68
    Also, just tried jumping the red and white at the tstat and I heard a click at the air handler, but no click at the relay. 
  • Erin Holohan Haskell
    Erin Holohan Haskell Member, Moderator, Administrator Posts: 1,982
    @tommygags - I've merged your duplicate posts into one here to eliminate confusion. Thanks.
    President
    HeatingHelp.com
    tommygags
  • pedmec
    pedmec Member Posts: 711
    Trace the two conductor back from the air handler to the taco zone control. The air handler has to switch the zone on at the taco 503. You might just have a broken wire coming from the air handler.
    tommygags
  • pecmsg
    pecmsg Member Posts: 3,532
    tommygags said:

    Also, just tried jumping the red and white at the tstat and I heard a click at the air handler, but no click at the relay. 

    You can jump out all you want, it's time to break out a meter and find where you're not getting the signal!
    tommygags
  • tommygags
    tommygags Member Posts: 68
    pedmec said:
    Trace the two conductor back from the air handler to the taco zone control. The air handler has to switch the zone on at the taco 503. You might just have a broken wire coming from the air handler.
    You were right!! Looks like the wire got unspliced in the wall/ceiling. Thank you for your help!

    Now to find the easiest way to run a new wire from the first floor to the second floor...
  • pedmec
    pedmec Member Posts: 711
    And that's why we don't put splices in the wall lol.
    tommygags
  • tommygags
    tommygags Member Posts: 68
    Finding all sorts of lovely gifts from the previous owner! Thanks again!