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Bad taco relay 24v?

mattyc
mattyc Member Posts: 44
in Thermostats and Controls
What are the steps to troubleshoot the 24v side of a taco switching relay? Just moved into new house with a single zone oil boiler   I bought and installed a taco 2 zone switching relay ( I plan on installing an indirect tank for zone 2) I wanted the relay to utilize the common terminal for my Honeywell lyric stat..I ran brand new wires as well directly to the boiler controls from the thermostat. After installing the thermostat, it would not turn on...I figured it just got banged around and broken while in the process of moving and I know the lyric stat is not the best in Honeywell’s lineup...so I buy a new thermostat and I get the same results. After some time with a meter I’ve established the thermostat wire has continuity and I have 24v between 24v and common terminal but the thermostat will not even light up.  Am I testing wrong? Low voltage issues have always been a week point for me. Also to be noted I still have the thermostat wired to the triple aquastat “TT”with the exception of the third wire to the switching relay common terminal   Thanks for any input

Comments

  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,214
    Your thermostat should be wired to the Taco SR502 and the XX terminals wired to the T-T in your boiler.

    Although the way you have it wired should still turn on the boiler.
    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
    HVACNUT
  • Big Ed_4
    Big Ed_4 Member Posts: 3,020
    Where did you pick up the common for the thermostat ? Do you see the terminal block top left in Alan's diagram , common on bottom terminal is were you pick it up. Power off when wiring ...

    There was an error rendering this rich post.

  • HVACNUT
    HVACNUT Member Posts: 6,335
    R and W on the thermostat connect to TT on the aquastat, and Common on the Switching relay connects to C on the thermostat?
    What's connected to R and W on the switching relay?
    Do as in the diagram above. But do the XX thing Only after you install the indirect. 
    If you're currently using a tankless coil and running out of hot water, wire in ZR,ZC instead, between the switching relay and the aquastat. It's  line volt switching there so use 14 gauge wire. It should be on a 15 amp circuit. If for some reason it's on a 20 amp breaker, use 12 gauge.
    By using ZR,ZC, if the boiler temperature drops below the low setting, it will shut off the heating circulator(s) in order to help provide enough domestic hot water. 
    Once you install the indirect, remove ZR,ZC and use XX.
  • mattyc
    mattyc Member Posts: 44
    Yes the boiler turns on as usual since I put the old thermostat that came with the house back together wired to TT on the triple aquastat and when I tried wiring my wifi therms I picked up the commin from the terminal block on the top left. I’m thinking that the terminal block on the top left is bad? But I may be testing it wrong. I’m not sure 
  • HVACNUT
    HVACNUT Member Posts: 6,335
    edited March 2021
     Is the circulator wired to the aquastat? It needs to be wired to zone 1 on the Taco relay as well. 

    The 24v terminal block is not bad.
  • mattyc
    mattyc Member Posts: 44
    @HVACNUT thanks I’ll try that. So my current situation when trying to wire my wifi stat that is, my circulator and Rh&W are wired to the triple aquastat and I was just wiring common on the thermostat to common on the switching relay...I was being lazy by not wiring everything to the relay but I assumed no reason why it all wouldn’t work. I don’t quite understand why it wouldn’t but I’ll wire it all to the relay with Zc Zr for my tankless and see what happens. Thanks 
  • HVACNUT
    HVACNUT Member Posts: 6,335
    If you swapped the wires at TT it might work, but it's not right. 
    You're dealing with two separate power sources. A transformer in the Taco and a transformer in the aquastat. They're butting heads at the thermostat and that won't make anyone happy. When things are idle, you'll get a back feed through the transformers coils and pretty soon it won't be pretty. 
    Alan (California Radiant) Forbes
  • mattyc
    mattyc Member Posts: 44
    @HVACNUT thanks I didn’t think of it that way.  Hope I didn’t mess up my new thermostat. Just bought a tekmar lol
  • Mike_Breault
    Mike_Breault Member Posts: 35
    @mattyc If your using a tekmar stat, might I direct you to this?
    https://www.watts.com/products/hvac-hot-water-solutions/controls/zone-controls/302p/302p

    Mike B (tekmar)
  • mattyc
    mattyc Member Posts: 44
    @Mike_Breault I think I’ll go that route in the future for sure once I zone my house better and add radiant. Thanks 
  • Mike_Breault
    Mike_Breault Member Posts: 35
    @mattyc Anytime and thank you for considering us.. I think you'll like it, a couple nifty features athat I really like is you can mix and match pump and Zone valve controllers, and the ability to leveraqe the away feature.. use 1 wifi stat like the 561 and low cost 519s, when you put the wifi in away, it triggers the 519's. low cost wifi system for Home / awat mode.

    Be well

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