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steam/no pressure

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Timco
Timco Member Posts: 3,040
in THE MAIN WALL
If your pressuretrol is set to .5psi, and it shut off at .5psi, then there is no problem. You would hear a vent hissing if it were stuck open.

Tim
Just a guy running some pipes.

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  • lanceL
    lanceL Member Posts: 14
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    steam/no pressure buildup

    Hi guys,
    With your help and the Lost Art, I'm slowly getting my one pipe to work like it should! After venting the mains, unplugging the pigtail, cleaning the low water probe, and installing a 3# gauge, I have another question. Boiler was hot, jumped the thermostat, fired for 30 min, and only saw about .5 psi from initial fire till I shut it down. Rads were hot. Pressuretrol at .5 to 1.5, mercury limit at 3.
    Does this mean some of the main or radiator vents are not closing, and it can't build pressure? When they fail is it in the open state? If a tenant has removed a vent will that cause this?
    Thanks for sharing your years of experience.
    Lance
  • Timco
    Timco Member Posts: 3,040
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    I should add that I see them fail in open state. As to tenant, if it was removed with even .5psi, they may be in the hospital with burns. If it was removed when cold, steam would shoot out the rad and make their apartment a sauna. Pretty scary to see steam shoot out of something...

    Tim
    Just a guy running some pipes.
  • David Nadle
    David Nadle Member Posts: 624
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    net steam production

    Lance, my system behaves the same way. 6 oz almost instantly after ignition and stays there for 30+ minutes. Then the pressure begins to build again, going from 6 to 11 in about 3 minutes. My vaporstat cuts out at 11 oz. I know from the days when my pigtail was clogged the pressure can go a lot higher. I think if a vent is not closed at 0.5 psi you will hear it hissing.

    My hypothesis for my own system (which is sized just right for the connected radiation) is that while the system is heating there is a near balance between steam production and condensation that keeps the pressure flat for a long period. When all the iron is finally up to temperature the steam cannot give more heat to it without being at a higher pressure and so it starts to rise again. This is the ideal preassure at which to cut out I would imagine.

    If this is correct then your system fills at about 0.5 psi, and ideally you'd want to cut out just above that level, something you can't do with a pressuretrol.

    Bottom line is if you don't have hissing vents and the house is comfy everything is OK, but you could save some money cutting out earlier with a vaporstat.



  • Jamie Hall
    Jamie Hall Member Posts: 23,399
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    Agreed...

    sounds like it's working remarkably well. You should be so lucky!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Edward A. (Ed) Carey_3
    Edward A. (Ed) Carey_3 Member Posts: 236
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    Vent in rad upstairs

    Lance,

    You post sounds like it a tenant property, and you are not sure if all of the vents are in place.

    You MUST have all of the vents in the rads when the system is making steam. If they are not, it could discharge a LOT of steam into the room. That much steam in an unoccupied apartment (people not home) could cause significant damage. If they were home, and let’s say they were sleeping when the boiler fires, it could really hurt someone if they were near the vent FPT on the rad when the steam discharges.

    When you are testing such a system, you must have access to the entire system and all of its components. Don't assume that all is well upstairs, or you could really have a problem.

    Ed Carey

  • Supply House Rick
    Supply House Rick Member Posts: 1,404
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    steam dammage

    a few minutes of open steam will remove all the wallpaper in a room. an hour could bring down the plaster!! it's essential to check every part of the system when testing!--nbc
  • lanceL
    lanceL Member Posts: 14
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    steam/no pressure buildup

    Thank you all for your input and safety alerts. I will be sure to check all vents are in place. Previously several large (60-72" long) radiators were run with no vent, and never emitted steam. now with the varivalves they seem to be heating further across.
    I haven't observed a complete boiler cycle since installing the 3# gauge, but yesterday it was not zero'd, and was straight down off the scale when firing. Is it shot, or can I readjust to zero? Hope my new gauge isn't toast! Thanks
    Lance
  • Unknown
    Unknown
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    Does your 3PSI gauge have a pigtail? It needs to be mounted on a pigtail to protect it from the steam. What about your 0-30 PSI gauge - What is the reading on it?
  • lanceL
    lanceL Member Posts: 14
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    Thanks Rod,
    Yes, the gauge is on a pigtail, which was cleaned and filled with water before use. The 30# was clogged and never has moved. I zero'd the 3# today and it seems to be ok. Thanks to all
    Lance

  • lanceL
    lanceL Member Posts: 14
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    Thanks Rod,
    Yes, the gauge is on a pigtail, which was cleaned and filled with water before use. The 30# was clogged and never has moved. I zero'd the 3# today and it seems to be ok. Thanks to all
    Lance

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