Gravity-return steam system???

Shane_2

Ok, for the second time this year, And the second time ever, I came across a two pipe steam system with air vents on every radiator. The first one looked similar to the gravity-return system Dan describes on page 125 of the Lost Art.


This second one, I can't seem to figure out what the installer was thinking. There are no thermostatic or F&T traps anywhere in the system. The return side of each rad is hard piped(no return ell, no union); so I don't believe an orifice is installed. The return mains are above the water line of the boiler (3/4"). The returns from some of the radiators are trapped with a dirt leg like I would install on gas piping for a boiler. I attatched a photo of one of these traps.

At this point, I will be repairing one leak on the return piping. The homeowner has reported no problems besides the leak. I found the system to be loud(hissing from air vents).

Any insight, experience, guesses, thoughts, or opinions would be greatly appreciated.

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Steamhead (in transit)

If there are orifices

they would be in the radiator steam supply valves- not the return ells. I bet there are right/left nipples in those return connections- that's the only way they could get them to make up without using standard unions.

Are the dry returns on this system vented?

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Shane_2

They used standard unions on the return piping.

No, there are not any vents on the returns.

Have you ever seen individual u-bends on the returns?

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Steamhead (in transit)

In that case

those might be very shallow "loop seals" that keep air and steam from jumping from one radiator to another thru the returns. They may be strategically located so they didn't need one on every radiator.

Think of what a sink drain trap does and you'll get the idea.

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