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pressuretrol use

New to this, but am loving learning new things about my steam system. I just installed gorton vents on my main, and from my calcs, think i am pushing out all the air (ahead of steam) with about 3-4 ounces of pressure. When the steam reaches the vents, they close and pressure builds up in the system. My pressuretrol is set at .5 cut-in and 1 dif. and the boiler has cycled off in longer cycles. By longer cycles, I mean in cycles when the system is raising the temp of the house by 5-6 degrees (we use a set back thermostat).

So, is this anything I should be concerned about, make adjustments for, etc.? The only thing I can really think of at this point is that the boiler might be oversized. Should I consider partially closing the ball-valve on the gas line?


  • Steamhead
    Steamhead Member Posts: 16,841
    Don't mess

    with the gas line, valve etc. Call a pro for this.

    How long does it take from a cold start before the boiler cycles off on pressure?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • arcalex
    arcalex Member Posts: 8
    run time


    Thanks for the response. The boiler will run about 45 minutes before the pressuretrol kicks. I left it alone last night and the pressuretrol cycled the boiler once per heating cycle. I did notice that the house was warmer than usual, but that could be more related to the fact that we are about -12 wind chill and the thermostat was working overtime...

    A quick question - since installing the gortons on the main, I have knocked down the pressuretrol to .5/1psi. Would that increase the radiators' ability to heat? In the sense that I am pushing less pressure through the system, I have moate (sp?) passive traps, and I would not be pushing steam to the returns causing back pressure? Just wondering.
  • Jamie Hall
    Jamie Hall Member Posts: 23,305
    The short answer

    is yes -- particularly with Mouat or other passive systems.  The lower the pressure the happier everything is going to be.  It's not an illusion!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Mouat Systems

    From what I've read, the Mouat System ran on "5 to 8 ounces of steam pressure".

    A lot of things about steam defy common logic so it took me a while to accept this - "Steam travels faster at low pressure than high pressure". (Page 17 - "The Lost Art....")

    Since you have a Mouat system, you might want to take a look at the following old book which has been scanned and is available on Google Books. Go to Google and paste the following phrase into the Search Window and that should give you the link. 

    500 plain answers to direct questions on steam, hot water, vapor and vacuum ...  By Alfred Grant King

    When you get on the Google Book page, click on the "little book" in the upper left hand corner and that will get you to the "500 Answers...". It's about 186 pages long.

    I found all the hand drawn illustrations fascinating!

    - Rod
  • arcalex
    arcalex Member Posts: 8

    Rod, Thanks for the source. I will check it out. I agree that some of the basic principles are counterintuitive. I read We Got Steam and the concept of the slower moving, higher pressure steam was explained very well...using school buses and cars as examples. My goal is to get the entire system to operate at those pressures. I am going to get a low-pressure gauge and see where I am right now. Might end up with a vaporstat to control it better. I have a feeling the previous owner and boiler guys cranked up the pressure and were blowing steam right through the traps, creating back pressure and leaving the last 2/3's of the radiators cool to the touch. They are not operating like that anymore. After doing the work for the install, I want to make sure this boiler lasts the rest of my time in the home...
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