I replaced a Columbia boiler with a Weil-Mclain CGA4 (basically same btu in/out). The house has fin tube baseboard which was installed with the Columbia when the house was built around 1957. The circulator pump is on the supply. After the pump there is an air separator with an auto bleeder valve. From the air sep, one output goes to the closed expansion tank (no shut off valve) and another feeds the baseboard. The baseboard is connected in a series (from what I was told) and only have bleeders on two baseboards in the upstairs bedrooms. A plumber once said that they are needed only there because they are at the end of the system. PSI was as high as 25 with temp at 180-190. Water was drained out of both baseboards upstairs with one getting very hot. The other one was warm. My questions are:
Should the pump be on the feed or return?
Should I put a shutoff on the expansion tank and drain it completely?
I was told by another plumber to attach a hose to the drain valve, open the valve to drain the water out and open up the feed water and let it run for sometime. Then shut off both valves and check PSI. This will make sure all of the air pockets are out.
P.S. The plumber supply store where I bought the boiler had no suggestions.