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2 zone circulators forced hot water system

bfd12732 Member Posts: 4
Hi, old house 1926 FHW boiler system. Original zone whole house (2 floors) one circulator all cast iron radiators all good. Added 2 story addition with all baseboard, 1st floor part of original zone still ok, new space a little colder but ok. 2nd floor new space is more isolated from rest of house probably most distant from boiler. This is the second zone. When running second zone even if 1st is not calling for heat the whole house gets too warm. Just to keep second zone comfortable often makes rest of house like sauna. Suggestions for remedy? hopefully NOT including new piping! PS Circs are on returns I believe.


  • bfd12732
    bfd12732 Member Posts: 4
    Also Thanks in advance for any help and guidance.
    HVACNUT Member Posts: 5,023
    You'll have to see if the 1st floor circulator actually runs when the 2nd floor zone comes on.
    Probably not.
    More likely is the 1st floor flo valve on the supply side is not seating properly.
    You can try loosening the bolt on top of the flo valve (dont back it all the way out).
    When the bolt is loose, run the zone on and off quickly about 10 times. Sometimes that will clear any debris hanging up there.
    If not, you'll need a new flo valve. You might be able to replace the insert only if it's a newer style.
  • GBart
    GBart Member Posts: 746
    Could be piped wrong too, pics are always helpful as is a warranty on the contractors work.
  • bfd12732
    bfd12732 Member Posts: 4
    The circulators run independently of one another as they should. I do not believe I have any zone valves just two circulators. I am not a heating expert but I know it is piped correctly. I saw the way it was installed when walls were open and know that the new zone is only connected to the second floor new area. I was thinking it may be convection causing water to circulate in the opposite zone, but thought the circulator itself ( the idle one) would stop flow in that zone.
  • Jamie Hall
    Jamie Hall Member Posts: 21,089
    An idle pump will not stop backflow. It's just a complicated spot in the pipe, as far as the water is concerned..
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • unclejohn
    unclejohn Member Posts: 1,824
    Need some pictures of pi[ping and pumps. You may be able to install a check valve in the pumps to prevent flow when off. Also @HVACNUT is talking about flo control valves or flo-check valves not electrical zone valves.
  • bfd12732
    bfd12732 Member Posts: 4
    Thanks, I do not have any flo/check valves now, that is what I was thinking may be needed to stop circulation in the idle zone. Does this seem possible? I have all winter to think it through at this point before I can drain down the system to install valves LOL.
    HVACNUT Member Posts: 5,023
    In your first post you wrote "PS Circs on returns I believe."
    If they are in fact on the return, then there should be some kind of flow control valve for each circ.
    Can you post some pics? Not too close.