Broomell system main vent to chimney to be eliminated

mstrbill

need a little help with quantity of main vents to get the air out of a vapor system in witch the vent from the condenser to the chimney will be removed due to Lining the chimney for oil to gas replacement . Situation is back in the 80s someone converted all the radiator throttling valves and put in open closed shut off valves to all but 3 of 23 rads . all of the vapor traps are original Broomell els . EDR is 860 . existing boiler is oil fired at peerless at 900 sq.ft . steam . Replacement boiler will be gas / 850 sq.ft steam . Has mercury vaporstat to reuse. Question is how to figure the cubic ft of air to vent and then turn that into multiple main vents . I know how to use Gerry Gills charts , method for pressure systems so should i cut the pipe into the chimney and wait for steam ? Count time , figure pipe size and come up with quantity , i am not sure if i should treat it as a pressure system when converted from pull to push of the main . Appreciate all who respond .

Steamhead

I'd start with two Gorton #2 vents at the condensing radiator, and add more if needed.