Main vent - nipple size adequate?

mitch101

When is a main vent nipple too small to take advantage of my two Gorton #2s? My Crown BSI103 steam boiler is oversized based on edr. Thermostat is set for steam heat but boiler still short-cycles several times per hour. So I threw out the old single main vent and made an elaborate antler to hold two Gortons as in photo. The Gortons are 1/2" but the nipple on the pipe is like 1/4" hence the nutty arrangement of adapters to downsize and hold the vents vertical. They're mounted at end of 30 feet of 2.5" pipe leading to final return. System is single pipe.

Steam reaches the farthest radiator pretty fast, but half the radiators upstairs hiss and the boiler short-cycles several times per hour while thermostat keeps calling for more heat. I lowered pressuretrol to 1.5 with a 1.0 subtractive diff after having it much higher (which was inefficient, I recently learned).

Should I hire someone to tap a 1/2" threaded hole (wall thickness concerns me though) or else to weld a 1/2" threadolet on, then plug the tiny 1/4" one? Or would 1/4" be big enough to release all the air the system needs to?

Fred

1/4" is adequate for two Gortons.Keep the pressure set low. How much is the boiler over-sized? Are you sure the pigtail the Pressuretrol is mounted on is clean? They will get clogged and pressure can get higher than you realize. Do you use a set back on your thermostat? If so, that is a problem on an over-sized boiler as it requires the boiler to run for longer heat cycles to bring the house back up to temp.

mitch101

Thank you, sir. I don't use a set back. I believe it's around 15% oversized. Next project is cleaning that pigtail and installing a T with a 0-3 gauge.