B&G NRF-25

ChipDryden

I am annoyed at the sound emitted from the circulator pumps that resonate throughout the zones. It's has a tone to it, not a whistle, like a medium pitched hum.

epmiller

Just a WAG, but is the distribution piping mounted tightly to to joists or otherwise tight enough against the floor structure to easily transmit noise? I’ve seen pipes hung with rubber isolators inside the hangers although I didn’t experiment with removing some to see if it was doing much. I have to look up the pump curve of that B&G to see if another idea I have might help. 

Is the boiler circulator a 3-speed? If so, slow it down one step and see what that does. If only one zone is calling for heat, that will take off less heat than if all zones are calling. If you slow the boiler circulator down it could affect how much heat is available when multiple zones are calling.

Ironman

Whats the delta T on each zone? More than likely, you're over-pumping.

ChipDryden

I've set the speed on (1) the lowest setting. I think at most 5 degrees delta T. It's a single story ranch house.

Ironman

Velocity noise + low delta T = over-pumping. Chances are, you could get by with one secondary circulator and 4 zone valves instead of 4 pumps. We would have to know the details of the system to confirm that.

fenkel

To determine if your pumps are incorrectly :
How many btu are in each zone?
Next how long is each.zone in feet..
Formulas to use:
Each zone btus divided by 10000, will determine gpms for the zone.
Next for same zone..
Total feet of zone x1.5 and then x.04   (.04 is used with 3/4 copper pipe) this will determine zone head pressure
Example.. zone uses 25000 btus and is 200 feet long
Gpms = 2.5
Head pressure = 12.0 psi of head pressure
Use these two number to look at your pump curves for the pumps considered..

ChipDryden

Thanks.

Robert_25

Try throttling the flow with the ball valve on the output side of the circulator.

ChipDryden

Thanks for chiming in. I tried that-It does dampen the tone somewhat but then creates a whooshing water sound at the valve. I was concerned that may damage the pump to I left the valve fully opened.

fenkel

Are you using flow control values?
Are the plastic ifc installed in pumps?

ChipDryden

Thanks for the suggestions.