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Boiler cycle every minute or 2

Hello , my boiler was installed about 3 years ago and now I notice it going on and off. After the first cycle I notice that it shuts off on low water. When it comes on again it will run for 1 minute and I can see all the water going down on the glass very fast and it goes below the cut off point. The boiler shuts off and again I watch the water comes back up within 1 minute and it fires again. After 1 minute it does it all over again and again. I drained my boiler once a month. Pressurettol is set to about 2 psi. It is not going off on pressure.  I need help. Thank you 


  • GW
    GW Member Posts: 4,692
    edited January 2021
    Ahh I didn’t read that thoroughly. Is the boiler piping good? 

    What I typed earlier-If you’re handy with a multimeter or electricity in general you can track down what’s causing the cycling. Jumping the stat is simplest. If it’s not the stat nor the pressuretrol, the low water cut off is the next candidate. Roll out (safety) switches would be the last thing to scrutinize. Ignition control is possible too. Then there’s always the mouse-chewed stat wires. Gotta just hunker down with the multimeter 
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
  • Jamie Hall
    Jamie Hall Member Posts: 23,276
    What, if anything, has been changed recently on the system?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • neilc
    neilc Member Posts: 2,703
    Imma gonna go with my standards,

    what's the boiler pressure on the gage while it's firing?
    have you checked the pigtail this season?
    is the water dirty in the sightglass?
    does it bounce much?

    post a general picture floor to ceiling showing the pipes also,
    and one closer in of the Ptrol controls, sightglass,
    known to beat dead horses
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    You need to verify the pressure with an accurate low pressure gauge, as the water level in the returns will rise 1.75 inches for each ounce of pressure. High pressure will temporarily rob the boiler of water, and this fluctuating water line can thermally shock the cast iron sections, and crack them.
    Your pressuretrol settings may have no relation to real pressure in the system.—NBC
  • Fred
    Fred Member Posts: 8,542
    I would suggest one of two possibilities:
    - Either the Pigtail, (the looped pipe that the Pressuretrol is mounted on) is clogged and the Pressuretrol can't manage the pressure. Or
    - The boiler needs to be skimmed. Has any new piping or anything been added to the system since last season? It sounds like there is oil on the surface of the water, making it difficult for the steam bubbles to break through and that is pushing the boiler water back out through the return. Draining the water out of the boiler does not get rid of the oils. They just cling to the side walls when you drain the water out and resurface when you refill the boiler.
    - Also, if you have the 404 Pressuretrol, (the gray box) set the cut-in to .5 or .75 and set the white wheel, inside the gray box to "1", facing the front of the box.