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Hydrostat 3250 Aquastat & Taco ZVC406 Zone Valve Control Wiring

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DIYCharlie
DIYCharlie Member Posts: 13
Possibly dumb questions, but here goes:

(System consists of six Taco Sentry zone valves/single circulator/no indirect water heating.)

According the diagrams as I understand them:

Power to the circulator is wired through the ZVC pump end switch and through the 3250 aquastat.
Does this sound right?

The "TT" wires run from the burner control to the TT terminals in the aquastat, and TT wires run from the "XX" isolated end switch terminals in the ZVC to the same terminals in the aquastat.
Again, is this right?

This is my second boiler install, to replace the first I did 30 years ago in our house. I'm a little rusty, but the ZVC is really the only thing that is new to the system set-up.

Thanks for any and all help,
Charlie

Comments

  • HomerJSmith
    HomerJSmith Member Posts: 2,468
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    ... TT wires run from the "XX" isolated end switch terminals in the ZVC to the same terminals in the aquastat.
    Yup.
    Power to the circulator is wired through the ZVC pump end switch and through the 3250 aquastat.
    Does this sound right?
    Nope. The aquastat provides the power to the circulator. The XX on the Taco ZVC activates the aquastat to turn on the boiler and start the circulator.
    There are relays that can control a circulator, but in your case, the aquastat does that job.

    STEVEusaPA
  • Steamhead
    Steamhead Member Posts: 16,899
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    @HomerJSmith is right. I'll add that the HydroStat can hold the circulator off for a few minutes so the boiler can heat up past condensing temperature, but that won't work if you power the circ from the ZVC.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
    EdTheHeaterMan
  • HomerJSmith
    HomerJSmith Member Posts: 2,468
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    All boiler condense at start up. It is sustained condensation that's the biggie.
    EdTheHeaterMan
  • DIYCharlie
    DIYCharlie Member Posts: 13
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    So 120V to circulator would be routed either (a) as shown here, or (b) direct to aquastat?
    Thanks again.



  • HomerJSmith
    HomerJSmith Member Posts: 2,468
    edited August 2023
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    Read my post! You can do it thru the Taco, but I prefer to do it thru the aquastat. In a Primary/Secondary sys the sys pump contacts on the Taco would power the load distribution circuit pump and the aquastat would power the boiler circuit pump.

    The TT on the Taco to the TT on the aquastat tells the aquastat to turn on the boiler firing and the circulator. You can choose how you want to do it.
  • DIYCharlie
    DIYCharlie Member Posts: 13
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    O.K., let me admit I'm a hard case, slow on the uptake and all that bad stuff.
    I guess what I am missing is what happens with the TT connections on the boiler relay (GeniSys 7505), which I perhaps mistakenly referred to as the "boiler control" earlier. Are they simply not used?

    Thanks for your patience.

  • HVACNUT
    HVACNUT Member Posts: 5,864
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    TT gets jumped on the Genisys. It should have 1 leg constant 120 volt to power the Genisys, and then 120 volt from B1 on the Hydrostat to limit on the Genisys. So switching is line volt. By jumping the 24 volt TT circuit, the burner is ready to go once B1 is energized.
  • DIYCharlie
    DIYCharlie Member Posts: 13
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    Thanks all.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,102
    edited September 2023
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    To add to the confusion:
    This set up is for a system that may have primary/secondary piping design or some other design where there is more than one circulator. The boiler control (Hydrostat 3250 in your case) might operate the boiler circulator, while the ZVC would operate the system circulator. You have only one circulator pump, so you would not use the ZVC pump switch relay.
    Hope this adds to your confusion, or at least makes things clear as mud.
    This comment brought to you by:

    Click on Spoiler

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • DIYCharlie
    DIYCharlie Member Posts: 13
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    Starting up the system now and having a couple of problems. Boiler starts up w/o any t-stats calling. When I turned one up, the boiler shut down. I then changed some wires around on the 24V circuit to what I think is right, and now I get fuse blow on the ZVC. Attached is the 24V wiring. Do I have my wires crossed? XX End Switch on ZVC T-stat side is wired to TT on Hydrostat and the T-stat terminals are jumped at the burner control, per above advice. THANKS again.



  • HVACNUT
    HVACNUT Member Posts: 5,864
    edited September 2023
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    Wrong thermostat. You're sending 24 volts via Y to common creating a direct short when the thermostat is turned below indoor temperature. 
    Remove the wires from C on the thermostat terminals on the Zone panel and from Y at the thermostats. 
  • DIYCharlie
    DIYCharlie Member Posts: 13
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    Yeah, it hit me a little while after I posted. I had done what you say and got it working correctly.
    Thanks for the reply.