Two pipe Steam gravity return

Dan Rieber

We came across a two pipe gravity return system (in a five story multi-family buiding that was rehabed 15 years ago) where some of the raditors have two control valves and some only have one. The other end having been capped. Should these valves be left all-the-way open? like in one -pipe Steam? We plan on replacing the boiler on this job, but we want to inform the building super (a young inexperienced, yet eager to learn guy) how this system should work.
Thanks to anyone who can advise.

Steamhead

Yes they should

fully open or fully closed.

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