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Radiator steam vents not closing


Contrary to everything
May 19, 2020
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Single pipe steam system. Radiator steam vents aren't closing when they get steam. Adjusting them helps but doesn't eliminate it.

This is a new problem developing over the past month or so. It's affected the radiators in order of whichever is furthest from the boiler.

I've tried throwing a new adjustable steam vent and a new non-adjustable steam vent on the biggest problem radiators. Those let even more steam by and don't even make an attempt to close despite being rated for 10psi

My 0-30psi gauge reads ~3psi and my 0-3psi gauge does a full turn and pegs on the stop so I'm thinking pressure is ~5psi or definitely way high for what a steam system should be but still well within the ~10psi max operating pressure of the valves.

What is the pressure reading at the furnace?

~5psi, according to the 0-3psi gauge that now reads 1.5psi at atmospheric pressure.

I'm gonna clean out the pressuretrol pigtail later today.
The only thing at the radiators is the steam (air, they're supposed to close when they hit steam) vents.

I just checked the pressuretrol pigtail. It's clean. Which makes sense since the pigtail tees off the same spot as the pressure gauges and those works fine and weren't too dirty when I went to install the 0-3psi gauge.
Tested the pressuretrol and it was cutting off at like 5 and on at 4ish. Way too high. Swapped in another pressuretrol I had on the shelf and that calmed things down a ton but the steam vent valves are still behaving somewhat poorly.

Anyone got any ideas?
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