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Taco hydronic heating thermostat not working

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Lowmiler
Lowmiler Member Posts: 2
in Domestic Hot Water
Our home has a Taco controlled hydronic system that covers the bathing/kitchen water, the heating of the home, and a bathroom radiant floor.

Suddenly the bathroom radiant floor thermostat, a Honeywell low voltage type, has stopped working. No display. All other water heating in the house is working fine.

The Honeywell thermostat has a red and white supply wire, connected to R and W, and I get 30V AC when bridging those wires. I get the same 30V at the other end of those wires at the Taco controller. To me, that suggested a bad Honeywell thermostat. I installed a new one, and that, too, won't power up.

Kind of lost on next steps in troubleshooting. Any guidance appreciated.

Todd

Comments

  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,013
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    With only two wires, your thermostats needs batteries. The 30 volts that you're reading is from only one leg of the transformer and won't power the thermostat.
    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
    rick in Alaska
  • SteveSan
    SteveSan Member Posts: 235
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    What is the part# of the Taco control? SR or ZVC? Is the green LED power light on? If you jump the R-W to one of the zones, does this turn your system on? Please give us a call 401-942-8000 and ask for Tech Support. We are here from 8am-5pm EST Mon-Fri.
  • Lowmiler
    Lowmiler Member Posts: 2
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    Alan (California Radiant) Forbes said:

    With only two wires, your thermostats needs batteries. The 30 volts that you're reading is from only one leg of the transformer and won't power the thermostat.

    Well, I guess the first set of batteries I put in were “brand new duds”, because I got home and tried another set and bingo, we’re back online.

    Thanks for the help!
    STEVEusaPArick in Alaska
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
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    Lowmiler said:



    Well, I guess the first set of batteries I put in were “brand new duds”, because I got home and tried another set and bingo, we’re back online.

    Thanks for the help!

    That actually happens often. Customer replaces batteries and it doesn’t work. I put in my batteries, it works.
    Another common issue is not locking it back on the base properly, and/or bending a pin.

    There was an error rendering this rich post.

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