Main Return Vents

Meowschmidt

Does anyone know the proper Main Return Vents to use on a 2-pipe gravity return system? I had 3 separate 3/4" vents with Hoffman 45's on them (I thought those were radiator vents!). I replaced them with 4A's to move the air out quicker, but they seem to still get enough heat to close during the heating cycle. Part of me thinks that these baby's shouldn't get enough heat to close on the return lines, but I don't really know. Also, why do I want a thermostatic trap at these points? Don't I want to allow air to move in-and-out of the system at this point?
Thanks for any suggestions!!

Steamhead (in transit)

Where in the system

are the vents located?

And are there traps on the radiator return connections?

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Meowschmidt

All the radiators have thermostatic steam traps. Most of the elements were replaced last year with B&J retrofit cage units. I'll try to get a picture of the area I'm talking about. Thanks for your help.

Steamhead (in transit)

There should be a vent

at the end of each steam main, and one serving the network of dry (overhead) returns.

For the mains, measure the length and diameter of each main so we know how much air is in each one.

For the returns- how many radiators are on the system?

"Steamhead"

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Meowschmidt

I have two separate steam mains terminating at roughly the same point in the room (one is a longer run than the other). I have a Hoffman 75 on one and a Gorton #2 on the other (since I did not have ceiling clearance for another Hoffman 75). Both steam mains fill quickly and the vents close within 1 minute of each other. I feel comfortable that those two legs are balanced well for the steam. The Dry return vents (which I had been describing previously) terminate in roughly the same area and are outfitted with Hoffman 4A's. All four pipes (2 steam and 2 return) drop straight down into a common wet return at this point.
The house is vintage 1931 and all the post-boiler piping looks original. 20-22 radiators in all, most being recessed convectors.

Steamhead (in transit)

Upgrade your dry return vents

to a Gorton #1 or Hoffman #75 on each dry return. Those 4A vents are just too small.

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