No heat upstairs

[bferro]

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.

Thanks.

[finnegan]

There is no accepted standard as to which side to put the pump. I think the supply side makes sense so you are pumping any air bubbles up and away as opposed to trying to pump them down and having them float back up against the pump. I would take the suggestion to try to fill and drain the system at the same time. Your problems are almost certaily caused by air and that may solve the problem.

[bferro]

Thanks I will try it on Sunday and post.

[jimmym]

I've also read in www.pmmag.com that you should pump AWAY from the expansion tank, not towards it.
Also, read up on Spirovent air separators, It says that remaining air in the system will be dissolved into the water and removed at the spirovent, make-up will be via the water fill pressure reducing valve. I always thought the the air would have to be entrained, not dissolved, to get separated out.

I don't know a lot myself, but I have a great memory for those who do.