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I have an old Vapor system that is not heating evenly. (half of the Rads. are hot and the other half are cool). This is a two pipe system with the inlet at the top of the rad with a Arco valves, and the outlet without any traps. The boiler is installed with a standard Pressuretrol (operating at about 1.5 lbs). I intend to replace this to a lower pressure control (to operate at about 10 oz.). The system has a few devices on the return side that no one seems to know what they are, one is made by "Moline":
I feel this is an Air eliminator. There is also another device:
, The system is piped as the attached drawings show. Need to stop water hammer and get the whole system to heat. Any Ideas??...