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Vapor System

Doobs Member Posts: 4
I was called to correct some steam radiator piping issues in a residence from the early 1900's.  It is a 2 pipe system with radiator traps and looks like it was originally a coal-fired vapor system.  >Steam main wraps around perimeter of basement and has Hoffman Differential Loop near boiler.  New Natural Gas-fired Peerless 63-5L Steam boiler on Natural Gas was installed 3 years ago, but boiler is running probably 2 to 3 lbs. pressure rather than proper vapor setup.

My question is this:  is it worth replacing the Pressuretrol with a Vapostat and and trying to get this current setup back to the way it was designed?  Is this gas boiler a good match for vapor pressure range? Short cycle?   Is there a significant energy savings to be realized by lowering the pressure?  Potential pitfalls?



  • Jamie Hall
    Jamie Hall Member Posts: 21,089

    If you have a differential loop on the system it absolutely will NOT work at over somewhere between 6 and 12 ounces.  You MUST put a vapourstat on that system.  Set it to begin with at 12 ounces with a 6 ounce differential.  Fire it up and let it run until pressure starts to build.  If the burner shuts off on the vapourstat before the loop trips (you'll probably know -- the return will get steam) you're good to go.  Otherwise, keep lowering the cutout until the loop does not trip.  Make sure your differential lets it cut back in.

    You will probably see a significant fuel saving.  More important, the system will heat much more evenly and rapidly.

    While you are at it, check for bad traps...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Doobs
    Doobs Member Posts: 4
    Vapor System Part 2

    Thanks, Jamie!

    Returned to correct some radiator piping pitch issues and really took a good look at the system.  The pressuretrol was set with cut-in at 2lbs. and dif at 1lb!  I cranked it down for now!

    The traps are 12 Hoffman #8's.  After tightening a leaking spud union I pulled trap cover off and Whoa! - no cage unit inside!!! Checked several others and they were there, but looked pretty ancient.   Had a serious conversation with homeowner about the work and cost of what needs to be done.  *New Vaporstat, cage units, low pressure gauge, main air vent....Trying to get them to by into the fact that they need to trust me and fix these things to make the system right.   It is a considerable expense to rectify issues.  The main vent is an ancient Hoffman Vapor/Vacuum vent.  It is funky and quite large.  Not sure how well it works.  Should I replace it and with what?  What about cage units?  B & J are popular up here in Maine, but what about Tunstall cage units?  Any feedback on cost/reliability compared with B & J?

    I"m excited to get this system right and I appreciate your insight!
  • Steamhead
    Steamhead Member Posts: 15,983
    That main vent

    is probably a Hoffman #11. The best replacement is a Gorton #2.

    B&J or Tunstall cage units/capsules will work in those traps. Be sure to get the right ones. Don't forget the crossover traps at the ends of the steam mains. If one main is longer than the other or is a larger pipe size, replace its crossover trap with a B&J #122A so it will vent out faster.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • Jamie Hall
    Jamie Hall Member Posts: 21,089
    One does wonder

    sometimes how the knucklleheads expected these things to work.  Hoffmann equipped systems are basically pretty simple -- and do a splendid job of even heat..  As Steamhead said, don't overlook the crossover traps at the ends of the mains; they are very important.

    A sigle Gorton #2 should be just fine to replace that old Hoffmann vent.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Doobs
    Doobs Member Posts: 4
    Crossover traps

    Nice call on the crossover traps!  I totally wiffed on those....

    Went back and checked.  This basement is pretty cluttered so I had some difficulty getting around.  You were right, near the ends of both mains - 1 Hoffman #8 crossover trap each!  These have definitely been long forgotten and neglected.