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short cycle

jtp Member Posts: 5
i have done some pipe replacement on this system...there were leaks everywhere....Now the system runs up  to 2 lbs in about 4 minutes ,shuts down,,,drops to 0 in about 30 seconds and back on......


  • Jamie Hall
    Jamie Hall Member Posts: 22,912
    At a guess...

    I would say that the venting -- whatever it may be -- on your system is very inadequate.  Or simply not working at all.  Depending on exactly what kind of system it is, the steam mains or the dry returns need venting -- lots of it.  Four minutes to run up to 2 pounds is very very short, and very much suggests either that the vents aren't there or they aren't working.

    And 2 pounds is too high a pressure, except for a very few rather unusual systems.  The cutin should be around half a pound, max., and the cutout a pound and a half -- max.  If you have a vaporstat, you can probably go even lower, again depending on the exact system.  2 pounds may be enough to close and hold closed whatever vents are there on your system, and you'll have very inadequate heat.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
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