Venting and cycling in one-pipe steam systems

Steamhead (in transit)

the boiler might need a water side cleaning.

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Peter Zelchenko_4

Venting and cycling in one-pipe steam systems

I have a question about one-pipe venting. Customer has a three-story building (about 50,000 cu. ft. total heating area), using a one-pipe system, about 16 radiators, with 168,000 Btu/hr. boiler. There are two vents above and near the boiler.

Last winter, we put Gorton No. 6 vents on several radiators in the cold basement (units are on the ceiling). The system was cycling pretty fast, about 3 minutes on/3 minutes off. That seemed too fast, but the system at least seemed to be "respirating" properly. (That's my fancy term for the venting and pressuretrol doing their collective job: I hear the last vent close, meaning the last air is out and radiators are getting all the steam they need; boiler pressure now rises rapidly to about 1 - 1.5 psi; pressuretrol then kicks in; flame stops until pressure drops down to the pressuretrol minimum; the cycle starts again. Does that sound correct?)

But suddenly it has been taking a lot longer than 3 minutes. More like 15 minutes. No change to the system. I hear some vents close to the boiler now taking a long, long time to evacuate air. What should I be looking out for?

Peter Zelchenko_4

We did that. No change.