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Taco SR 501 wont turn on boiler

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parkingnotice
parkingnotice Member Posts: 16
This is a radiant floor system. Have new Thermolec TMB boiler replacing Hydro Shark boiler. The HS was switched from a Taco SR501 which started the pumps, which ran the water through a flow meter, which kicked on the boiler. There were no TT connections inside the boiler itself. The Thermolec works differently and has its own pump relay and control board with C and W1 contacts inside the boiler. C and W1 on the boiler are wired to 6NO and 5 on the Taco as per the Taco and the Thermolec diagrams. I have 120v into the Taco. I have 24v at the TT terminals in the Taco. The Taco is on (green light), I call for heat (red light) and then nothing. I thought the Taco, when TT calls for heat, is supposed to switch 6NO and 5 and send signal to boiler. I am getting 0 volts between 6NO and 5 all the time, Taco on or Taco off.
What am I missing? Am I supposed to be getting any reading between 6NO and 5? Or do I need to jump 24v to 5?

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  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    edited April 2018
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    Don't jump 24v to 5.
    What do you have on H and 3?
    Why can't you just wire the thermostat to C & W1? Why do you need the relay?

    There was an error rendering this rich post.

  • parkingnotice
    parkingnotice Member Posts: 16
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    My Thermostat is a Tekmar smart thermostat. It needs its own 24v supply. As per the Thermolec instructions I have to provide my TStat with its own power and use an isolation relay to switch the boiler.
  • unclejohn
    unclejohn Member Posts: 1,833
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    It should work if wired as you described. Double check wiring and try jumping 6no and 5 boiler should start if not check boiler.
    Zman
  • parkingnotice
    parkingnotice Member Posts: 16
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    Ok. Thanks. I did try to jump 6NO and 5 and nothing happened. I will check the boiler when I get home.
  • unclejohn
    unclejohn Member Posts: 1,833
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    So your tstat is wired to the isolation relay coil and the TT contacts of the Taco control go through the relay contacts.
  • unclejohn
    unclejohn Member Posts: 1,833
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    Make sure boiler is in the Electric only position.
  • parkingnotice
    parkingnotice Member Posts: 16
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    Yes. My Tstat is wired to the TT terminals of the Taco plus the Com. It is a Tekmar smart Tstat. Smarter than me.
    The 6NO and 5 then go out to boiler C and W1.
    I'm not sure what you mean by "electric only position" except I think you are referring to the Thermolec boilers that are dual-fuel. This one is only electric. Is there still a switch? I'll look for that when I get home. There wasn't anything about that in the manual.
  • Zman
    Zman Member Posts: 7,607
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    If Jumping the electric boiler does not start it, I would start looking at the safety's. A flow switch or high limit....
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • parkingnotice
    parkingnotice Member Posts: 16
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    I just found a note in the troubleshooting section. This wasn't in the manual at all. I found the troubleshooting pages in the brochure, but not the installation manual. Go figure. I do not have a load management control. I'm going to try and jumper the S1 and S2 when I get home.

  • parkingnotice
    parkingnotice Member Posts: 16
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    Ok guys....S1 and S2 jumpered. Nothing. Ran through the testing sequence. I have no power on the 24v side of the transformer. So that's that. Brand new boiler. Contacted the manufacturer.
  • unclejohn
    unclejohn Member Posts: 1,833
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    Don't be mad at me but you do have 240v to boiler correct.
    delta T
  • Alan (California Radiant) Forbes
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    That's a good question......
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
    delta TSuperTech
  • parkingnotice
    parkingnotice Member Posts: 16
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    Hilarious. Yes, of course. 240v on 60amp double pole breaker.
    It was in fact the transformer. Dead on arrival. You’d think it got tested before it left the factory. Cest la vie.