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or at least I think it's velocity noise. I'm installing a replacement cold start boiler. The new boiler was shipped with a Taco 007 pump, and as I have two baseboard circulator controlled loops, I bought another 007 to use on the second zone. I kept the supply size at 1 1/4 in. to the pumps. The pump discharge is 3/4 in. , as is the zone piping. At the boiler return, each zone goes to 1 in. and then back to 1 1/4 at boiler. I didn't figure head loss on zones, but they should be fairly well matched as one one is 315' and the other 275'.
I haven't fired the boiler yet, but circulating the system and bleeding air, I'm getting a lot of rushing noise at the pumps. I don't think it's an air problem as I have bled and bled.....When I choke each zone down with the return side balance valves, about 40%, the noise pretty much clears up. Is this an acceptable way to run, or am I going to have premature pump failures? If I do, what size Taco pumps would you replace the 007's with ? I'm too close to heating season to change any piping if I can get away with what I have for this season anyway.......Thanks for the help.