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1-pipe system; 2-pipe rad; 1-air-valve
So a friend of mine just moved into a new place .. with a Bryant Mfg. 9-443 boiler (I'll leave you to look that one up ;-) )
Anyhow, besides the fact that several of the radiators include closed-tight Hydronic "bleed valves" instead of air-vents ... (knuckleheads) .. they have a few very loooong old rads (about 10-12ft long) that have floor inlet valve on *both* ends and it seems, only 1 air-valve (at *one* end) .. no traps (fyi)
Unfortunately, these old gals are also within "built-in" rad covers so I can't see the middle bits very clearly, but I can only presume that it is a straight-through rad and not 2 rads uncoupled in the middle.
Anyhow, the question, how to vent? ... (I don't have my TLAOSH nearby, perhaps this is a known Dead Men problem)
Should there be a vent at each end?
Should I close 1 floor inlet (opposite the vent at the current end)?
Should I double-maximize the venting?
I presume that as the steam moves through the main, the steam enters the near end of the rad, and the rad begins to consume and condense (nd allow air to escape the far end down-riser(?) .. then the steam continues down the main and enters the main on the other end and now the rad is consuming and condensing on from both ends, and both risers are now supporting condensate and steam and no place for the air to escape .. so now there's an air bubble in the rad and no escape (except for a closed hydronic bleed valve) .. and if I were to replace with a regular steam vent, it would only be vented on 1 end, and presumable close very quickly due to steam entry very close (6inches away) .. You see my problem? The perfect place to vent would be in the rad middle .. but I don't have access and if I did have access, I don't thnk there are vent ports in the center .. hmmm ..
Anyhow .. I'm sure this house will present other head-scratchers ... happy to hear your thoughts.