Author Topic: High Pitch Resonance in Heating Pipes  (Read 1470 times)

Offline RozBujnik

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High Pitch Resonance in Heating Pipes
« on: December 21, 2017, 11:19:47 AM »
Looking for source of resonance in heating system pipes.

Furnace: Raytherm 134 WT natural gas boiler.

Background: Armstrong S-25 pump with MF/BF bearing assembly, and motor - 1750 rpm, was causing vibrations and resonance. Replaced with wet rotor 3-speed Bell Gossett NRF25. Current brand new components:

B&G wet rotor NRF25 circulator
Watts EXT-30 Expansion Tank (12PSI)
Watts 335-M2 PRV (30PSI)
Watts 9D Backflow Valve
Watts 1156f Pressure Regulator (12 PSI)

Cold system pressure: 12PSI. Running pressure, when bitterly cold outside, approx 17 or 18 PSI, boiler temperature under 125F.

There is no detectable vibration. The circulator is perfectly quiet. There was no resonance after circulator installation, but the following day resonance re-appeared. Sound pitch changes depending on the pump speed selection. Low tone on speed 1, and higher pitches on speeds 2 and 3. System needs only speed 1.

Purged the system of air. Bled the rads. No vibrations. No hammering. No banging. Only the resonance. It's hard to pinpoint exact location but appears to emanate from elbows, where horizontal basement pipes turn to vertical to upstairs rads. No humming / resonance at furnace. Hear it in the basement and on ground floor, not on second floor.

What could be the cause?

Offline Admin

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Re: High Pitch Resonance in Heating Pipes
« Reply #1 on: December 21, 2017, 12:05:43 PM »
What size are the water pipes and what is the maximum flow rate in GPM?

Try decreasing the water pressure and if this helps it's likely the water pipes are undersized for the maximum flow rate, GPM.

Offline Hgye

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Re: High Pitch Resonance in Heating Pipes
« Reply #2 on: December 21, 2017, 01:14:48 PM »
I would also try cleaning any check valves.