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I just bought a house with steam heat I replaced the main vent with a gorton #2 and all the air vents on the rads and a few were not working a few were hoffman #2's. The house was an estate and the parents of the family that lived here didnt not use the 2nd floor for anything but storage and were unable to comment on the system heat output. A there were a few leaks on on rads tightened the spuds and bought new hoffman 1a valves. the boiler was installed in dec 2014 and the owner passed away in 2018 and the house just sat. I have a tech coming out when they have time to perform a yearly maintenance check. I plan on insulating the main lines as well wondering if i have enough main venting or need more.
It is a one pipe system.
The blue lines in the drawing are return lines and red is for steam.
The three rads in the upper right get hot first and the one in the top right in the loop gets almost all hot and have the valve set to slow and the upstairs ones to fast, and the ones in between set to the 3 or 4.
considering moving the thermostat upstairs.
We are working towards remodeling upstairs currently so its not occupied.