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Modulating pressure issue

Acon12
Acon12 Member Posts: 3
in Gas Heating

I have a low pressure Burnham 3 pass firetube stream boiler with a Gordon-Pratt 12S burner. I adjusted the modulating pressure control to modulate the boiler around 4 psi (with additive diff) with the operating control set a 6. I can see the boiler gets to low fire in the modulation, but the boiler still trips on operating pressure of 6 and begins another cycle. I would like to run longer cycles and have adjusted the mod pressure down at times to see if it holds a consistent pressure, but it continues to top out. Any idea why that is?

Comments

  • ratio
    ratio Member Posts: 3,789
    If the pressure is rising, you're making more steam than you're condensing. What application?
  • Acon12
    Acon12 Member Posts: 3
    ratio said:
    If the pressure is rising, you're making more steam than you're condensing. What application?
    I’m overseeing an old elementary school. 1920s build and 65,000 sq ft. There’s about 20 radiators throughout and I have a little over a dozen reheat boxes that heats air pushed into the classrooms. Theres a couple preheat coils if needed. The strange thing is, I have twin boilers, and my boiler 1 runs and modulates with little to no cycling. They share the same one pipe system
  • bburd
    bburd Member Posts: 1,039
    It sounds like the low fire setting on your modulating burner still produces too much steam for the system at low heating loads.
    —
    Bburd
  • Acon12
    Acon12 Member Posts: 3
    bburd said:
    It sounds like the low fire setting on your modulating burner still produces too much steam for the system at low heating loads.
    Definitely a possibility. I’ve run the manual fire rate adjustment in minimum and had it top out as well. Any suggestions to remedy?
  • bburd
    bburd Member Posts: 1,039
    The remedy is beyond my experience I'm afraid, but others here will probably have a good idea.
    —
    Bburd
  • retiredguy
    retiredguy Member Posts: 976
    That is a Gordon-Piatt burner that could be fired with gas or oil. You need to call a burner tech company and see if the low fire firing rate can be set a little lower. If not, just let it cycle on/off. Some of those units had pilot lighting problems which were always a nuisance.
  • ratio
    ratio Member Posts: 3,789
    Are the two boilers identical? Clock the meter/check pump pressure at low fire to see if they're actually firing at the same rate. How are they connected together?

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