Air Vent Placement

Matthias

I am working on a one-pipe steam system where we recently replaced the boiler. We are unable to locate the return pipe except where it enters the utility room, as the basement is finished with drywall and the crawlspace is inaccessible.

A bedroom in the house remains very cold, and the radiator does not heat up unless the system runs for several hours. This suggests a lack of proper main air venting. I have identified a section of straight pipe near a decommissioned garage radiator that appears to be upstream from the affected bedroom.

Ideally, a main air vent should be installed 18 inches before the drop to the wet return. Since we cannot locate the return line, would installing a main air vent at the furthest accessible point on the steam main effectively resolve this issue?

Jamie Hall

Wouldn't hurt anyway… the actual point is to get the main vent AFTER the last radiator takeoff. How far after is quite irrelevant.

mattmia2

it may/likely is a pocket of water sitting somewhere that they steam can't progress past until it evaporates the water.

Matthias

Thanks @Jamie Hall. I didn't think it would matter.

@mattmia2, never thought about that. Do you think it has to do with a loose hanger? Wish I could investigate further but everything is closed in.

After I posted this question, I started wondering whether this may be a counterflow system. However, the 3/4 return coming low into the heater room makes me think otherwise. Could some parts of the system have a return lines and some part be counterflow?