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Balancing a dual loop single-pipe parallel-flow wet-return steam system.

system includes a 30' extension on loop2 truncated w/ a #75 vent. Aiming for a 4 minute vent of mains, An 8-10 minute closure on all 9 radiators after 178000 BTU nat gas firing of a PB 63-64 boiler... size 04.. @ 1 oz. pressure. System has 500 sq. ft [EDT] of cast-iron 3-column radiators. Once clean, intend to install 9 hoffman 1A vents, and adjust. See enclosed spreadsheet [.xls file] showing details that lead to hopefully 8 minute closures of all 9 vents. What do you think? Anything amiss here? Currently in need of balancing, as rooms vary in temp. and vents are widely intermittent in the 3-story 4-bedroom 1900's house. It's working but its likely inefficient, as it whistles, hisses, and sometimes allows a room to cool, or overheat. Burners are clean, blue to yellowtips, and water usage is up due to vents allowing steam to sometimes pass for minutes at a time... Furnace, pipes, radiators all in nice shape. Vents painted, and in immediate need of replacement. Sight glass too high, cloudy, but not muddy. Ready for a good cleaning. This week!

Thanks for looking. Critiquing comments welcome. Encouragement appreciated. Engineer type, tool guy, not new to plumbing, hvac, vehicles, furnaces, forced air or hot water, elec, gas, coal, wood, or oil, but kinda new to single-pipe steam.
three story twin, 1890, one addition 1960. One pipe system. 3 column radiators, 4 bedroom, two bath. MidAtlantic states. P.B boiler. 8 years old.
heat vent chart (2233).xls


  • Jamie HallJamie Hall Member Posts: 10,383
    Only thing I'd suggest is that you will need a nice big main vent or two at the far end of the L1 main, and another couple of big main vents at the end of the extension, where you show the little one. Then start playing with the radiator venting to get the response you want in each room...

    And keep the pressure down!

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
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