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Where to put electrical safeties on hydronic zone controls

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sre92
sre92 Member Posts: 15
in THE MAIN WALL

Where do you put the electrical safety switches (thermal switch like firomatic, and LWCO) when wiring the relays for hydronic systems with zone circulators? How about with zone pumps?

Taco instructions show these safeties protecting both types of relays for SR50x-5 and ZVC40x-5. However, it would be nice if the smart thermostat would stay powered when there is a system failure which triggers one of the safeties. That way, the thermostat could alert you when the system is not producing heat after a call for heat.

Do you keep these thermostats powered? Do you do it by powering the thermostat separately, or by wiring the safety devices only to the burner, not the zone relay?

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 27,223

    Power the thermostat separately. In fact, if I had those things I'd have them on a completely separate breaker or fuse…

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • HydronicMike
    HydronicMike Member Posts: 321
    edited February 5

    All safeties are wired in series. Depending on your system they can be all line voltage, or a mix of line and low voltage.
    If your thermostat has a C wire and batteries, it won't lose power (display). Most wifi thermostats will then alert you if temperature isn't being met, or there's a wiring issue, but won't tell you that a zone control failed or some other error. You would need more advanced controls for that.
    Modern oil burner primaries, and some power gas burner primaries have alarm contacts when the burner locks out, which you could wire into an alarm panel or some other way to alert you.

  • sre92
    sre92 Member Posts: 15
    https://forum.heatinghelp.com/discussion/comment/1886401#Comment_1886401

    If the safeties are all wired in series and powering the zone relay, then a smart thermostat like an Ecobee would not be powered.

    Yes I understand that the thermostat won't directly say that there was a failure, only that the zone is not warming after a call for heat.

    The point of my question is to find out if people wire the zone controls as recommended, and forgo the "zone not heating" notification, or do it a different way.

    I'm asking because, on the surface, it seems like a good idea to put some of these safeties only on the burner, not the zone controller. I don't see a technical reason to have the firomatic ahead of the zone controller. I can imagine that the LWCO might be good to have though, since you could burn out circulator pumps by running them dry.

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