Bleeding zones in hot water system

Discussion in 'HVAC Heating & Cooling' started by construct30, Dec 24, 2007.

  1. construct30

    construct30 New Member

    Jun 16, 2007
    NorthWest PA
    Does anyone know of a good site or want to take the time to type the steps for bleeding the zones of a hot water boiler.

    The system I need to do has the bypass, tank and pressure on the return side, then the pump, the pump might be after the boiler I will have to check, then the boiler then out of the boiler to the manifold split into a ball valve, zone valve, ball valve, tee with boiler drain valve then out around the loop then back.

    1. Do you have to run the pump while bleeding?
    2. Do you bleed each zone one at a time?
    3. What about the pressure when you are done do you need to do anything to bleed off the house water pressure?

    I've plumbed several system using engineered plans, but always left the flushing and bleeding and electronics to the heating companies. I have to replace a couple of damaged baseboards in a garage and figure I should get a little info on flushing and bleeding that zone myself. I think there are 5 zones total on the system. I didn't plumb it.
    Last edited: Dec 24, 2007
  2. Furd

    Furd Engineer

    Jul 3, 2007
    Retired energy systems engineer
    Wet side of Washington State
    Never let the pressure rise above 30 psi or the safety valve on the boiler will lift.

    Depending on how a system is piped it may require bleeding with the circulator off or on.

    Again, depending on how it is piped you may need to bleed each zone individually. Do the heat emitters (baseboards or radiators) have individual bleed valves?

    System pressure when cold is usually about 12 psi. This may be a bit higher if it is a three or more level house.
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  4. construct30

    construct30 New Member

    Jun 16, 2007
    NorthWest PA
    It is all baseboard.

    I will be replacing some damaged sections so I need to flush that zone when I am done. The air bleeding is easy once that is done.

    Sorry I should have been a bit more clear in my original post. Thanks for helping I will check out the system tomorrow and get better info.
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