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All radiators are hot but boiler still runs for a long time (90-150 mins)

ImYoungxD Member Posts: 130
System is one pipe
I replaced the main vent with Gorton 1 soon to be replaced with Big Mouth
All radiator vents are replaced
I have a 0-5 PSI gauge with new brass pigtail and pressuretrol cut in 1, differential 1.5. 30 PSI gauge works well.
Boiler was oversized but tuneup guy changed nozzle from .75 x 45B to .65 70B and did not run combustion analysis. Had water hammer but no more now. I am making sure the next tuneup guy has an combustion analysis.
Planning to insulate mains later.

The issue is that my boiler runs for at least 90-150 minutes until the pressure reaches 1.5 then turns off. All radiators are hot (200f+) at 30-45 minutes. Is the boiler wasting oil or is how is it's supposed to be? I should mention that when the PSI is between 0.7-1.5, one or two of the 1st floor vents hiss and close (ping noise). They are Hoffman 40. Maybe vents are defective?



  • Jamie Hall
    Jamie Hall Member Posts: 23,675
    Could well be running just as needed. The radiators need to stay at temperature long enough to heat the space... I just posted a paper on the topic!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Fred
    Fred Member Posts: 8,542
    Why was the nozzle size changed? Was the boiler over-sized and short cycling?
  • ImYoungxD
    ImYoungxD Member Posts: 130
    edited January 2018
    @Fred plumber probably knew the boiler was oversized (120,400~ BTU). It was short cycling after I cleaned the pigtail and made adjustments to the pressuretrol (thanks to your guide). No more steam/water hammer as well after he changed the nozzle but no combustion analysis was done. I was questioning on why the burner stays on for so long but it looks like it's a normal process.