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How long between cut out and cut in?

Hey guys.



I was just wondering what the normal time between the cut out and cut in was for your boilers. My boiler cuts out at 10 ounces and cuts in at 4 ounces. But, all this take is exactly 1 minute.



Should my system be holding pressure a little bit longer?

Comments

  • TeachMeSteam
    TeachMeSteam Member Posts: 128
    Additional Info

    Also, then after it cuts back in, it takes about 2 minutes and 50 seconds to get it back to 10 ounces before it cuts out again.
  • boiler_man
    boiler_man Member Posts: 21
    What type of system?

    Do you have a tank less coil?
  • TeachMeSteam
    TeachMeSteam Member Posts: 128
    nope

    There isn't a tankers coil hooked up.



    My basement mains aren't insulated so I know that is a contributing cause but can that be the only reason?
  • Mike Kusiak_2
    Mike Kusiak_2 Member Posts: 604
    Seems normal

    Provided you have adequate venting and you are removing all of the air from the system on the initial call for heat, the cycling seems pretty normal. After the pressure hits the high limit of 10 oz, the steam in the system collapses and condenses rapidly until the cut in pressure is reached and the burner fires again.



    Based on the fact that your cycle time is one minute off and three minutes on ( 75% duty cycle ), it would imply that your boiler is about 33% oversized compared to the system's ability to condense the amount of steam produced.



    Does the pressure cycling occur during a normal call for heat or only during a recovery from setback?
  • TeachMeSteam
    TeachMeSteam Member Posts: 128
    Cycling

    The short cycling occurs during the normal heat operations. During a cold start up, it will take perhaps 20-30 minutes before it cuts out.
  • Jamie Hall
    Jamie Hall Member Posts: 15,740
    In answer to the original question is one minute

    unusually short -- the answer is no.  It doesn't take long for your radiation to happily condense the steam which is available in there!



    As Mike noted, though, your boiler may be slightly over fired.  You might be able to try downfiring it.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • TeachMeSteam
    TeachMeSteam Member Posts: 128
    true case

    Thanks for the info, guys.



    I'm curious. then what is a true case of short cyling?
  • Jamie Hall
    Jamie Hall Member Posts: 15,740
    To a certain extent...

    it's in the eye of the beholder.  Which isn't much help.



    However -- (and these are just my opinion!)



    If the boiler starts to cycle on pressure before all the radiation is warm, you definetly have a problem.  Probably inadequate venting.



    If the thermostat doesn't let the boiler run long enough, but then kicks the boiler back on in 20 or 30 minutes, that's a problem (with the thermostat).



    If all the radiation is warm, and the boiler is cycling on pressure with less than a 50% duty cycle (say a minute on, a minute off) that's a problem -- probably too big a boiler.  But... in this instance, the too big a boiler may be related to poor or missing insulation on the steam mains -- requiring a big boiler just to get things warm in the first place.



    And then again... it's in the eye of the beholder!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
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