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Difference between a Hoffman 4A and a MoM #1?

Jells
Jells Member Posts: 576
in Strictly Steam
I have a MoM #1 vent on a straight 2.5" pipe that runs up through 3 baths, it's their only heat. It's failing, bleeding steam the entire heat cycle, so I ordered a 4A, figuring why use the same model that failed. But the port on the 4A is much smaller than the #1, probably 1/8 the area. How can these both be called "main vents"?

Comments

  • BobC
    BobC Member Posts: 5,502
    The 35 was fine back in the coal fired boiler days because people usually kept steam up all winter. Modern steam boilers that only fire intermittently need larger vents for mains and risers.

    One #1 vents about 3X as fast as the 35 does. Buy either a Maid o Mist or a Gorton #1, I've used both and one is as good as the other.

    Bob
    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • Jells
    Jells Member Posts: 576
    Great, I'm already confused. On Supplyhouse there's 2 different Hoffmans, the 4A I have and the 45, not the 35 you mention. Is "35" another name for the 4A? The 45 is described as a "convector valve". Neither say what the port size is. Why do they make it so hard to spec these products???? The Hoffman "selection guide" page is utterly useless. How hard would it be to rate them by port size or air volume at a certain pressure? It just adds to the voodoo nature of steam IMO.
  • BobC
    BobC Member Posts: 5,502
    Sorry for the confusion, the 35 I mentioned is made by VentRite

    Hoffman 4A vents at 0.133 cfm
    VentRite 35 0.110
    MOM #1 0.330

    I don't know what the 45 is rated at but I suspect it's between the 4A and the 35 vents above.

    Bob
    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • Jells
    Jells Member Posts: 576
    edited December 2017
    Thanks Bob, but where are you finding these CFM ratings, that's exactly what I need! Even the damn Hoffman "selection chart" doesn't have that!

    Do you have any idea why they make a distinction between radiator and convector valves?
  • BobC
    BobC Member Posts: 5,502
    Years ago two of the sites members put together a chart on balancing and venting, it contains a lot of useful info, if you search the site you will find a link to it.

    The difference beween radiator and convector air valves is the radiator valves screw into a vertical surface while convector valves screw into a horizontal surface.

    Bob
    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • Steamhead
    Steamhead Member Posts: 17,387
    The Hoffman #45 is roughly comparable to the #40. It's a very small vent.

    With that said, what pipe size is this riser?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • Jells
    Jells Member Posts: 576
    I think in this case of the riser pipe itself being the radiator, I'm not looking to balance anything, just get the most heat out of it by the biggest vent practical. A big Gorton main vent would be silly though.

    Any ideas why a 3 year old MoM would fail?
  • Fred
    Fred Member Posts: 8,542
    Why do you think the MOM has failed? It may have has some dirt blown into it that prevented it from properly seating. Try washing it out and see if it closes.
    MilanDRomanGK_26986764589

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