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Wiring for Circulators, Zone valves and Thermostats


As a new Guy I'm hoping someone can answer a wiring dilemma I have found myself in,

I am installing an in floor heating system in a garage using an on demand hot water heater (rated for radiant systems) It is activated by water flow and I'm at a standstill until I can figure out how to wire in the circulator pump. I have 3 Honeywell V8043E Zone valves with end limit switches and 3 Honeywell T87F thermostats running on 24 Volts, I have a diagram to connect these components from Honeywell (see Below).

The problem then arises that I need to have 120 Volts to power on the Circulator Pump (single Pump for all 3 zones) How can I step up the 24 V signal from the end limit switches to the line voltage required for the pump? I have looked at installing an Aquastat However I would have no high and low temperature settings and I'm not sure if the C1 and C2 would still give me the line voltage I require. I've looked at the Taco 3 zone switching relays (SR503), But they provide a separate 120 V out for each Zone and I've already installed the 3 zone valves (24V) with one 120v pump. I'm not sure If I can use an SR501 Single Zone and just attach the Red Wires (end switches) in series to the thermostat (R and W Terminals) Would this give me 120V to the Circulator? and if I used this setup would I still need a 24V transformer to power the thermostats and Motors on the zone valves, The diagram I had planned to use for the Zone valves and Thermostats is Figure 14 Found here:


Does anyone know if this setup will work? I'm at a loss as to where to go from Here. Any help would be appreciated.



  • Jamie Hall
    Jamie Hall Member Posts: 18,924
    Figure 14 -- or for that matter any of the figures work. The end switches are just that: switches. They are not electrically connected to the zone valve operator. You power the operator(s) and thermostat(s) from a transformer as shown. The end switches are powered from a separate 120 vac supply, and can be used to control a 120 vac circuit to the circulator or burner or whatever-- circulator, most likely, in your case -- and can be wired in parallel.

    Note that this is 120 vac power wiring. It MUST be protected with suitable fuses or circuit breakers, and MUST be installed in accordance with your local electrical code.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • garageaddict
    garageaddict Member Posts: 2
    Thanks Jamie!!
    I guess I was overthinking it!!!
    I am planning on having my electrician do the final hookups but I'm doing all the sourcing of components and running of wires to cut down on costs, Do I need any other components to hook up the Pump and Zone valves (IE a Stepdown?) or is this something that can be hooked right into a dedicated 15 Amp circuit first?

  • Ironman
    Ironman Member Posts: 6,868
    I'm not sure if the zone valve terminals and end switches are rated for high voltage.

    I'd recommend one of two methods:
    1. Daisy chain the end switches in parallel and connect them to the "R and W" terminals of a pump control such as a Taco SR501. Then connect the pump to the high voltage pump terminals. Or
    2. Get a Taco ZVC403 zone control panel and follow the instructions. It will do it all.

    On another note:
    Please beware that you have the wrong appliance for space heating. A tankless water heater is not designed, controlled or approved for space heating. Your gonna have problems and a short life expectancy with no warranty. In spite of what some internet peddler may say in order to get a quick sale.

    Think about it: if a tankless water heater could take the place of a boiler, there would be no need to make boilers. You'll be much better off in the long run with the right appliance - a boiler.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Snowmelt
    Snowmelt Member Posts: 1,334
    I agree with iron man get the zone board. It well worth the headache and there set up to trouble shoot. That's the best part. Make it iddiot proof. You really have to use a boiler for a heating application. The wall mounted utica are nice. What tankless brand do you have?
  • SWEI
    SWEI Member Posts: 7,356
    Three zones in a garage?
  • Rich_49
    Rich_49 Member Posts: 2,692
    You require Taco ZVC403 not SR503 .
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • wmtandson
    wmtandson Member Posts: 62
    the more information that is provided the better help you will receive.
    Model number of heater is a good start