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Main Vent decision

Hello all, I need some help with choosing the correct main vent. Background: Victorian house 3000 sf (14 radiators total) but, I have 3 on the 3rd. floor closed / old American Standard boiler / 31 ft. long main 3" diameter.  Right now there is only (1) Hoffman #75 10 psi. at the very end of the main. Boiler sits toward the front of the house, main going to back of house. Can I use a Vent-Rite #75 5 psi. or stick with the Hoffman #75 ? 


  • BobCBobC Posts: 4,970Member
    Too small

    A 31ft long 3" main contains 2.6 cu ft of air, a Hoffman 75 is much to small and the Ventrite would be worse. The Hoffman 75 is rated at 0.5CFM while the Ventrite 75 is rated at 0.19cfm.

    I suggest building an antler with 2ea Gorton #2's and the Hoffman 75 to vent that air FAST. The Gortons have a 1/2" thread so you will need adapters if using 3/4 pipe to build the antler.

    The boiler pressure should be 1.5 PSI or less for efficient operation.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
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