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Pressuretrol cycling fast?

I have a Utica 112,500 btuh boiler, installed two owners back circa 2003. It heats the 2nd floor of my 2-family home, but the piping was clearly designed to heat both floors when it was first installed sometime in the 50s. As such, the boiler's one size too big for the current EDR, but it was the smallest steam unit Utica made in 03.

Last year the tenants racked up nearly $300/mo for gas due to lack of maintenance on the previous owner's part and lack of foresight on mine. Nearly every valve was solid with mud, including the pop valve. Total mess. I'm lucky that one rad vent gave out and vented all that pressure into a spare bedroom, and my tenants had never lived with steam heat either, so they waited until February to text me that something might be wrong.

Tenants didn't want me to fix anything until it got warmer, given that the system was working, albeit very inefficiently. I got it serviced over the summer, and this year the pressuretrol is actually doing something, but I'm worried that the cycle's a bit too short. From cold, the boiler will fire for 30 minutes to an hour until all the vents close and it reaches 1.5psi. From there it cycles every 3 minutes...90 seconds firing, 90 seconds off...until the thermostat stops calling for heat. This is great for gas usage because the tenants not only run the thermostat up to 75, but also have a bad habit of improperly locking their windows, causing major drafts. They actually still have their air conditioners in, and its almost December.

Is it bad for the system to cycle so fast? If so, is there any straightforward way to lengthen the cycle time? The whole main and all but one riser are insulated. I have Maid-O-Mist 6's on every rad, and MoM 1's on each of the long and short mains (2 main vents total).


    EBEBRATT-Ed Member Posts: 15,544
    Sounds like an oversized boiler. The next time you are their see if you can catch it on an off cycle. Run it until the pipe leaving the boiler just starts to get steam hot.....then see how long it take to get steam to the end of both mains. That will tell you if the main vents are large enough.

    Also check the water level when steaming. How much does it bounce? Shouldn't be more than an inch or so.

    Pictures of the piping around the boiler will help
  • Jamie Hall
    Jamie Hall Member Posts: 23,324
    That doesn't sound at all bad in terms of cycling, given your situation. The on/off cycling frequency you mention does tell you that the boiler is almost twice as big as you need -- but you knew that. It also suggests that the venting is adeqauate.

    It does waste some fuel, but not all that much -- perhaps 5%.

    If this were owner occupied, I would suggest that perhaps you could make some difference -- a small difference -- in fuel use by putting a time delay on the restart after cycling off on pressure, and this would lengthen the cycle time (though not the total time the boiler fires). However, this would take some experimentation to find the correct time delay, which would be hand on. Perhaps more to the point, in today's climate you as the landlord might be faced with some unfortunate arguments from the tenants that you are not providing adequate heat when and how they want it, and that you don't need.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England