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honeywell yhr845a switch and taco 571-2 head

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d0eby
d0eby Member Posts: 11
i have a honeywell 845a switch to control circ pump. and taco 571-2 head to open for zones. Everytime i think i have it figured out, something tests weird. please correct me with what is wrong. It is wired the same on all 3 zones. the circ pump works fine when it is called to turn on. i have 24 volts at the tt on the honeywell. (thought it was just supposed to be a straight connect together, no voltage.) the taco head has 24 volts on pin 1 and 3. which is only supposed to be like that after the valve opens, it has it as soon as the breaker is turned on(not open). the 2 pin that needs power to open for water flow, gets no voltage with pin 1 ever. so water valve never opens,(pin1 and 2 powered) but already has the voltage at 3, which should have power only after valve opens, and it never does. brand new head, so problem is in wiring.(same with 2 new ones) could a bad switch control be backfeeding power to my water flow head? i looked at diagrams for honeywell install, they are wired a way i understand, and the taco 571-2 wiring i understand, but together it seems like they dont mesh.

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  • HVACNUT
    HVACNUT Member Posts: 5,863
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    Where are you getting a common wire from on the RA845?
    1 and 2 on the zone valve gets power (24v) on a heat demand, then 3 closes the end switch to start the circulator.
    TT should read 0 on a heat demand, not 24v.
    STEVEusaPA
  • d0eby
    d0eby Member Posts: 11
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    yes, thank you. i figured it out, had 3 bad heads, 1 bad honeywell switch, and 1 bad circ pump, and 1 bad thermometer. Thats why i was getting all sorts of different voltages in the 3 zones. Luckly got 1 zone working right, and just kept checking other zone's voltages against that, to find the all the other problems. You did hit my biggest problem figuring out, that tt has 24volts, then 0 volts while heat call... thank you for answering so quick..
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    edited December 2018
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    That's alot of bad. You better keep digging. What's the VA rating of your transformer?
    Are you sure it wasn't a power surge or some other bad wiring/short?

    There was an error rendering this rich post.