Where are my main air vents?

Erock7625

Hello, been reading Dan's book and understand most of the boiler parts but had some questions on air vents and other devices connected to the lines.

It's a 2 pipe Weil McLean LGB-6 boiler, I did find one air vent on a return line near the boiler but that is the only one I've found. Are there supposed to be more and any on the main line as well?

Also what are these devices on the return lines and also on the lines between the main and return lines?

Thanks!

Steamhead

@Erock7625 , this is a Vapor system. There should be traps at the ends of the steam mains that direct air into the dry (overhead) returns. The air goes out that one vent you found, which BTW is too small.

Is there a condensate tank and pump that returns water to the boiler?

Erock7625

yes there is, when you say at the ends of the steam mains, is that at the very end? I can see the main for about 75 feet before it gets to the house and goes up through a wall and I can't see anymore of it.

Steamhead

That tank also acts as an air vent. It also explains all those traps installed on the vertical pipes.

Out at the end of that 75-foot pipe, before it goes up, is there a radiator trap piped between the steam main and the dry return?