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Hoffman Equalizer Loop

BM12 Member Posts: 3
This old boiler has no equalizer, it has a Hoffman Equalizer Loop which is only piped to one return out of 3.

Its connected to the 4" Riser.

The returns all go into the bottom of the boiler.

Its a 2-pipe system if that makes any difference.

Should I remove it and pipe the new boiler with Equalizer or leave it somehow?


  • Jamie Hall
    Jamie Hall Member Posts: 23,276
    Equalizer loop?

    I've heard of a Hoffman Differential Loop -- in fact, the system I maintain has one -- but not an Equalizer Loop?

    It sounds to me as though you may have had some repiping done in the past, which may have left little evidence.  The Hoffman Differential Loop system did have an equalizer pipe, in the usual way.  The Differential Loop was connected to the dry return (all dry returns merged into one at the boiler), and there was -- and should still be -- a good sized vent right there as well; that was the only vent as such in such a system.  It also tied into the header or riser, and by another pipe into the wet returns.  Sounds more complicated than it is... you might want to take a look at http://www.heatinghelp.com/files/articles/1662/Hoffman%20Heating%20Equipment.pdf -- look on page 12 for a nice explanation of the system.

    There is no real harm to taking a Differential Loop out, so long as you have a vapourstat or some other way to control the pressure to less than 12 ounces or so.  Otherwise, if this really was a Hoffman equipped system, you may find that water backs out of the boiler into some of the dry returns, which is not happy. 

    In this instance, where it sounds as though the dry returns may have been repiped at some point and don't all join together, you might be better off to repipe the new boiler fully conventionally, and use a vapourstat for control.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Steamhead
    Steamhead Member Posts: 16,832
    The Equalizing Loop

    was the early version of the Differential Loop. 
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • BM12
    BM12 Member Posts: 3

    Hi Jamie,

    It's definitely a hoffman equalizer loop, I read it off the casting.

    I looked in my Lost Art of Steam Heating, not there.

    I wish I took a picture of this boiler while I was there.

    I need to go back and look again.

    It definitely has been repiped and changed.

    Ed Grant
  • gerry gill
    gerry gill Member Posts: 3,078
    It has no moving parts

    other than its accompaning air vent..might as well leave it as it will work just as well today as it did when installed..
    Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

  • Jamie Hall
    Jamie Hall Member Posts: 23,276
    See Ed?

    I told you Steamhead or Gerry would have the answer!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
This discussion has been closed.