Steam Heat 1 pipe to 2 pipe conversion

gbp

I have a one pipe steam heat system that had the radiators on the 1st floor converted to a 2 pipe baseboard years ago.Each baseboard section has a vent at the opposite end of the feed/return lines. Ever since this was installed, the baseboard radiators have been banging(they are properly pitched).Someone told me that a 2 pipe baseboard should not have any vents, just traps on the return line. Is this true?

Steamhead

It Depends

If all the return lines from the baseboard drop below the boiler water line before connecting to any other return or return main, you put vents on the baseboards but don't use traps. This setup is called 2-pipe air-vent.

If they connect together before dropping below the waterline, you need traps on the return connections and NO vents on the baseboards. In this setup, a large vent is placed on the return main before it drops below the waterline. This setup is just called "2-pipe", or at very low pressures (under 1 pound), "Vapor".

Have you been able to isolate the exact location where the banging occurs?

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gbp

Venting & banging

The banging seems to only be in the lines to/from the baseboard. The return lines are above the boiler water line where they connect into a return to the boiler. So, do I need a trap for each baseboard and does that trap go in the return line of each baseboard before it connects to the boiler main?

Steamhead

Yes, trap the returns

and install a main vent on the return before it drops below the waterline.

Also make sure the steam lines are properly pitched.

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