Radiator vents open and close repeatedly

jimb245

Lately my radiator vents are opening and closing repeatedly, especially during the initial part of a cycle. The open and close times are around a minute or so. The vents hiss fairly loudly when open and make a noticeable sound when they close. The vents were replaced a few months ago. The radiators are single-pipe. Anyone know what could cause this and whether it means something is amiss?

nicholas bonham-carter

What make of radiator, and main vents are on the system?
What is the pressure of the system?—NBC

dopey27177

Your steam pressure may be set to high.

Your boiler pressure should be no more than 3 PSIG with a 1 pound drop back.

Jake

jimb245

The embossing on the radiators is American Radiator. The main vents are Dole Valve No 3C - they probably havent been serviced for a long time. The pressure gauge on the boiler always reads zero so guess it's not functional. The cut-in pressure setting on the pressuretrol seems to be at the lowest point (picture attached) and the cut-out wheel shows a "1" when viewed from the opening of the box.

Hap_Hazzard

I think a 3C is for convectors, like a Hoffman 71C. That's pretty small for a main vent.

jimb245

Thanks. Guess I need to get the vents and pressure checked.