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Boiler cycling questions

lutorm
lutorm Member Posts: 78
Hi again,



I finally got all the parts I needed to add a 0-3 psi and replace the dead 0-30 psi gauge for my 1-pipe steam system. The 3 psi one is on the same pigtail as the pressuretrol, the other one on its own. The pigtail to the pressuretrol was also totally gunked up with about 4" length of black goo that took a while to clear out. After putting everything back together, I cranked up the thermostat and sat down to see what happened. I'm trying to understand what's going on and if there's anything that can be done to make the system run more efficiently.



First: Long before pressure builds and the radiators even are hot, the boiler cycles regularly 10min on / 1min 30s off. What causes this? Is this something the thermostat does or something in the boiler, and is it desirable? (When it shuts down, the "test" LED on the LWCO illuminates. ) It doesn't make sense to me why this would be good, since if there's no pressure and the temperature is still not up, why shut down the burner?



Also, during that shutdown, the pressure sometimes goes negative by a one or two tenths of psi (judging from how much below zero the needle on the gauge is). Is that normal or should the vents open under vacuum?



Then: Once the pressure started building, the pressuretrol started cycling. It's set to 0.5psi cut-in / 1psi diff, which in reality apparently meant 1.8 / 1. After some mild force on the spring holder to be able to loosen the spring further, I got it down to 1.3 / 1. But the cycles are really short, about 2m 15s on / 1m 30s off. Is this normal or does this mean the boiler is oversized?



It seems the size of the boiler wouldn't affect how fast pressure drops after the boiler cuts off, so that 1m 30s has to be set by the heat loss of the system, right? So even if the boiler was smaller, it would still only cut out for 1m 30s (but run longer, of course). Does that make sense?



Any hints would be much appreciated.



/Patrik

Comments

  • Charlie from wmass
    Charlie from wmass Member Posts: 4,238
    The early cycling

    is in the LWCO not in the burner or the pressuretrol. Are your main line vents up to specs?
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
    https://heatinghelp.com/find-a-contractor/detail/charles-garrity-plumbing-and-heating
  • lutorm
    lutorm Member Posts: 78
    Hardly...

    ... given that there are none. I'm putting in a Gorton #2 tonight or tomorrow.



    But why does the LWCO cycle the burner? And how would it depend on the main vents?
  • Mark N
    Mark N Member Posts: 1,094
    lwco

    Is it a hydrolevel cycleguard? That how they work. Go to their website watch the video that explains it.



    Mark
  • lutorm
    lutorm Member Posts: 78
    ITT probe LWCO

    The LWCO is an ITT probe-type. I can look up the exact model when I get home.
  • DavidK_2
    DavidK_2 Member Posts: 129
    If the LWCO

    light comes on, then it is probably sensing low water - and hence shutting off the boiler.

    At least that is how my LWCO works - light comes on to indicate low water, and boiler is shut down. Does the water level go down while doing this cycling?



    It could also be cycling on the thermostat (if the thermostat is anticipating more heat) but it doesn't sound like it in your case. Easy to test, just set the thermostat to 90 and see

    if it makes any difference.
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,238
    Yes model number would help.

    If it is the test light not the low water light coming on it is to make sure the condensate is coming back to the boiler as it runs. Also it checks that the LWCO is functioning as it is designed to.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
    https://heatinghelp.com/find-a-contractor/detail/charles-garrity-plumbing-and-heating
  • lutorm
    lutorm Member Posts: 78
    Test light

    Yeah, it's the test light, not the red "low water" one. That video was informative, now it makes sense to me why it would do that.
This discussion has been closed.