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Circulator control

dvg
dvg Member Posts: 2
Replacing old gravity boiler with wall hung condensing boiler in small (1200sf.) house.---2 pipe, single zone, big pipes, cast iron radiators.----wall hung pipeing instructions says use primary/secondary----Asumming the one only room thermostat controls the boiler and primary circulator and the system remains single zone, what and how is the secondary circulator controlled?------Is P/S really needed?-----Is there some major downside if I don't use it?

Comments

  • Leon82
    Leon82 Member Posts: 684
    The boiler can usually control both or a taco switch ing relay can control the primary pump also.

    But one zone only you probably can omit it if the math works for flow rate thru the heat exchanger
  • Leon82
    Leon82 Member Posts: 684
    It will be worth it to spend time tuning the outdoor reset
    Canucker
  • JUGHNE
    JUGHNE Member Posts: 11,042
    If it calls for P/S piping, you need it.
    I have done a couple of these with Lochinvar water tubes.
    Their wiring allows for boiler pump and system pump.
    If system pump current exceeds the rating of the internal boiler relay, then another external relay may be required.

    Have you reduced the piping down in size at the boiler for the existing piping?
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,452
    You need primary secondary. You can start and stop both pumps with the thermostat.

    Make sure the amperage draw of both pumps does not exceed the capacity of the internal boiler relay.

    As @JUGHNE mentioned you can use a relay if needed to allow this to happen
  • dvg
    dvg Member Posts: 2
    So to be clear, p/s pumps are supposed to start and stop concurrently and not independently!
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,452
    Yes, no reason they cannot start and stop at the same time