Pressure Buildup in Main Vent

tomold

Hey all,

Recently bought a house with a two pipe steam system and am learning its ways. I've never had steam before and have tried to educate myself by reading We Got Steam Heat, but I'm a little concerned by something my system is doing.

When the system kicks in, there is a pressure buildup of anywhere from 2.5 to 5 psi, during which time no steam is reaching the radiators. Then there's a very loud "PSSSHHH" from what I think is the only main vent (pictured). The pressure immediately drops and the radiators come to life!

This works out ok when going from a cold house first thing in the morning, but when trying to maintain a daytime temp, the system often doesn't run for long enough for the whole pressure build/release to happen (which i think is due to the thermostat being in a room directly above the boiler area).

This all seems weird and contrary to Dan's advice in the book about these systems running best at the lowest possible pressure. So my questions are: 1) is this normal? and 2) what is this vent/trap contraption (pictured)?

Thanks!

Steamhead

Looks like a Webster system. The little thing on top of that cast-iron device is a vacuum check, and I'll bet it's sticking. Unscrew and remove it, and I'll bet the problem goes away.

tomold

Thanks for the response! Will give it a try.

neilc

that vacuum vent may or may not be noisy, but, if we're talkin 2 - 5 psi, shouldn't we be looking at the pigtail and Ptrol / Vstat?

can you post a picture of your pressure control so we see the settings, and how it connects to the boiler