Main Venting. Two Pipe Steam

PTTG40

Dunkirk Gas Boiler. Two pipe Steam.
This 2" main has about 16' of pipe from the boiler. Should I put a main vent at the end where it is capped off right before the elbow that extends to a second flr radiator ?


Thank Peter

nicholas bonham-carter

Are there crossover traps on the dry returns?
If they are not working, the air will not escape.--NBC

PTTG40

Yes I believe so. See attached picture. This is at the end of the largest main and runs down to the low return line on the ground.

Jamie Hall

Good -- there is a crossover trap, shown in your second photo there. There is also a vent shown there, which shouldn't be there, but it likely won't hurt anything. There must be a good big vent at the boiler, though, where that dry return drops to the wet return. Otherwise, you will have a counterflow situation in the dry return, which it wasn't meant to have.3

Check to be sure that the crossover trap is actually working. It's easy to do. When the system fires up, you should feel steam heat right up to the trap inlet -- and not beyond. No heat up to the inlet, trap is failed closed. Steam heat beyond? trap is failed open...

Steamhead

Actually that vent is in the right place. It lets air out of the dry return. The trap placement is incidental- it just happens to discharge down into the tee where the vent is mounted.

Whether the vent is big enough is another story.

nicholas bonham-carter

If the crossover trap is working, then you may not need a vent, but just an open pipe. Has a vent always been there, or is it a later bandaid. As a vent, its capacity is surely to small for the system.--NBC

PTTG40

Thank you all for the responses. First thing, the Hoffman Vent was added after I put a new trap only bc I had an extra Hoffman on hand and the tee was capped so I figured it couldn't hurt add it. Jamie: At the boiler I do have two vents a Hoffman 75 and a Gorton #1. Per your advice it seems when the boiler fires up the return line is getting very hot where the trap is on the crossover and beyond. Even though I just replaced this one last year you think it could be failed open already ? Should I get one that has a higher psi rating ? Seems that steam is getting into the low return line bc it is very hot.

nicholas bonham-carter

On a vapor system, you should have only a couple of ounces of pressure.
put on a 0-3 psi gauge from Valworx, and then you will know where your pressure is.--NBC