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New Burnham Mega Steam short cycling, only heating half the home


I just installed a Burnham Mega steam. I did a heat loss and properly sized. It turned out to be the same sq. ft. of steam as the old boiler. The boiler runs for a short period of time and never builds up a full head. It turns off a little early.

Has there been issues with the short cycle control on the boiler. I was told I could bypass, even take off control? Is this recommended? I am sure it will work if I did this. I do not want to take away form the integrity of the system and the way it is meant to work.

Any suggestions would be appreciated.


  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,578
    edited March 2014
    Short cycling

    If you remove the pressuretrol, you will only be addressing the symptom, rather than the cause. Maintaining the steam pressure between an upper, and lower limit is essential.

    This boiler could heat properly piped radiators with a few ounces. Did you put a good low pressure gauge on? What is the pressure the burner cuts out at?

    Quite likely, your main (not rad) venting is not allowing the air in the system to escape with no resistance, and causing the boiler to short cycle as you burn more and more fuel to force the air out of some constipated little openings. This resistance is measured as back-pressure of venting, and should be 1-2 ounces.

    Alternatively, some LWCO controls will cycle the burner off every 20 minutes or so, to check the water level at rest, but I think your problem is pressure.

    Did you follow the piping instructions, and skim it properly?--NBC
    STEAM DOCTOR Member Posts: 2,012

    How was the heat with the old boiler? If home heated properly with old boiler then you need to determine what changed.

    There are many thing that can cause only part of a home to heat properly. Anything that causes wet steam can lead to such problems. How is the near boiler piping? Was the boiler skimmed?

    How is the venting(main and radiator)?

    You mentioned that you did a heat loss. That is not the correct way to size a steam boiler. The only correct way to size a steam boiler is based on the heat output of the connected radiation(BTU output or EDR, different names for the same thing).

    Short cycling. Is it cycling on pressure or do you have a cyclegard that is periodically shutting down the boiler. Do NOT bypass the pressuretrol. If its the LWCO then you can replace it with a conventional LWCO. If its cycling on pressure the you need to determine why(assuming that it really is SHORT cycling and not going through the normal cycling process).

    Pics would help.