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boiler on / off cycle? too much?

You may have ab oversized boiler for your radiation. I would possibly suggest down firing the boiler. You may have too large of a nozzle . If the nozzle is 1.50 down fire to 1.25 and try that.


  • Ray_2
    Ray_2 Member Posts: 21
    Boiler on /off to often?

    Trying to be sure all is operating properly with my system. Not sure if this is normal...

    1 pipe steam, Burnham Pin5sns-me2 boiler,L404a honeywell pressuretrol. Gas

    system fires up runs approx 20 min builds 2.5 psi pressure turns off boiler
    -2 minutes later pressure @ 1psi - boiler turns on again

    -2 minutes later hit 2.5 psi boiler kicks off

    - minutes pass pressure goes to 1 psi boiler kicks on again

    This cycling on / off every 2 minutes continues till the house reaches temp -

    I use a honeywell programable thermostat. Pipes are insulated. Boiler water in sightglass bounces about an inch while operating( not violently). I believe Vents operating properly. 7 radiators on system, all get hot.

    Is this cycle normal - If not any ideas / thoughts?

    Thanks ,
  • Allan_2
    Allan_2 Member Posts: 18

    from the little i've been reading here.. doesnt seem normal. seems like you should be running fine at 1psi to heat the entire house. sure the main vents are working right?

    Burner Short Cycles
  • Boiler cycling

    Without knowing what size your radiators are, it would be difficult exactly what may be going on. First off, there should be no need for 2-1/2# of pressure in a system of this size. Lower pressure is always better for operation. Based on the statement that you only have seven radiators and a PIN5 boiler, I would have the size of the boiler checked in comparison to the connected load (radiators). It may a number of things causing the initial long cycle such as improper venting combined with a possible oversized boiler causing the shorter cycles while maintaining pressure. You are going to have to have that checked out. Hope this helps.

    Glenn Stanton

    Manager of Training

    Burnham Hydronics

    U.S. Boiler Co., Inc.
  • Dwayne
    Dwayne Member Posts: 4

    Possibly over sized boiler maybe.
  • Ray_2
    Ray_2 Member Posts: 21
    oversized boiler ? EDR correct?

    First A quick thanks for responding to my post - I gather from your message 2.5 PSI is too much. With the pressuretrol currently on the system I can not go any lower. So a more sensitive Pressureteol is recommended?


    I looked into what would cause my short cycling:

    one possible problem would be a dirty pig tail - What other symptoms would I see that would indicate the pigtail as the problem?

    The other possible cause that was mentioned is oversized boiler - I believe I have this issue.

    I did the following to calculate the load on my boiler-
    measured radiators - all 23 inch high, they are tube type 5 tubes per section. Used an EDR chart to find "3" as multiple to use to get SQ FT EDR per section. calculated SQ FT EDR for each radiator and multiply that by 240 BTU / HR to calculate Steam design output per radiator. Came up with a total of 43200 BTU / HR out for radiators for entire house. piping is 40 ft of 2in main, approx 50ft of 1 1/4in branched to radiators. Mains are insulated and have a Gorton #1 and vent Rite #35 to vent. So I"ll throw in an additional 4000 BTU HR for pipe?- so 47200 BTU / HR of load if I did this right. My boiler lists DOE NET 358 sqft and steam= 86000 BTU HR. Bottom line is if I did my calculation correctly my boiler is oversized by almost 40000 BTU? Did I do this right? Can a boiler be down flamed that much? Is that safe / wise?

    For what it is worth I also calculated what size radiators I should have per room - Sq ft of room * 45, compared to radiator btu / hr output. Sizes seem right except 1 room.

    Any feedback / advice would be great,
  • Anthony Menafro
    Anthony Menafro Member Posts: 197

    I'd lean towards an oversized boiler being your problem.

    Anthony Menafro
This discussion has been closed.