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Supply valve position

gyrfalcon
gyrfalcon Member Posts: 179
in THE MAIN WALL
Should this be open or closed during normal usage?
Slant Fin Galaxy GG100(1986) , 2 zone hot water baseboard, T87 Honeywell thermostats. 

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 24,842
    Unless there's a pressure regulating automatic feed valve in line, closed.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • gyrfalcon
    gyrfalcon Member Posts: 179
    Thank you, Jamie
    Slant Fin Galaxy GG100(1986) , 2 zone hot water baseboard, T87 Honeywell thermostats. 
  • hot_rod
    hot_rod Member Posts: 23,378
    There is a pressure reducing valve built into the top of that expansion tank fitting, called a Fill Trol. If it is working the shut off valve could be left on. It requires a special expansion tank for that fitting.

    It is a very controversial question whether to leave a fill valve on or off :)

    My opinion is to leave them open to assure the boiler remains at the required pressure, when air vents out for example, water needs to be added.

    If you chose to leave it off, it would be wise to have a boiler low water cutoff switch
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • gyrfalcon
    gyrfalcon Member Posts: 179
    So the fill trol will prevent boiler water from going back into the dhw? 
    Slant Fin Galaxy GG100(1986) , 2 zone hot water baseboard, T87 Honeywell thermostats. 
  • hot_rod
    hot_rod Member Posts: 23,378
    gyrfalcon said:

    So the fill trol will prevent boiler water from going back into the dhw? 

    The cutaway shows a spring check in the water connection.

    Approved, listed backflow preventors should be used when potable water is directly connected to a boiler.

    I don’t know if that is a listed backflow device. It would be indicated on the component, a tag or shield.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    gyrfalcon
  • gyrfalcon
    gyrfalcon Member Posts: 179
    I just emailed Amtrol and this was the response;

    Zach,

    It will prevent heated water from backflowing into your cold-water line. You need to keep that valve open to ensure makeup fill water will make it to the boiler.

     

    Slant Fin Galaxy GG100(1986) , 2 zone hot water baseboard, T87 Honeywell thermostats. 
  • hot_rod
    hot_rod Member Posts: 23,378
    Certainly any of the fill valve manufacturers like the see their valve able to do its job, me included :)

    The check valve I see in their cutaway is similar to what you might find in a BFD, he did not mentioned if it is an approved BFD, so I suspect not.
    Now it comes down to whether you are comfortable with the valve being left on, and the backflow protection it offers.

    If you had any chemicals in the boiler I would be more demanding that you have a listed BFD. It protects you and also the public if you are connected to the city without their BFD protection.

    Twice in my career have seen glycol come out of a potable water faucet from a boiler backflow, so it does happen.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream

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