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Help with humming, very long run / high head
We have an unusual setup that was put in in the 50's/60's. It's a third floor baseboard, one continuous loop all the way around, about 250 feet, with LOTS of turns, and about 1750sq feet, in Delaware, so 61000BTU's give or take. It's also 30ft of rise, plus another 80 feet of pipe (40 each way) from the boiler, so total loop is 375ish feet, 3/4in copper. The pump is a Taco 009-F5.
The problem is: The rooms above the boiler and pumps, which is in a wing of the house, hums something awful. I mean AWFUL. House is from 1855, so no insulation. System bleeds fine, no apparent air in any of the 3 circulators on that boiler.
I've had multiple people look at it and noone has had any GOOD suggestions. Anyone have a recommendation of someone REALLY good at hydronic systems in Philly / Delaware?