Hot Water Cylinder noise - ongoing mystery

[chrissando]

Open thread to try and solve an ongoing mystery which has been ongoing for over 12 months.

Moved in to our new build house in Sep 2021. Brand new Hot Water Cylinder fitted weeks before. Every time hot water is being heated we have a constant bussing / humming, loud enough to be heard throughout the house.

The noise is coming from the cylinder, not the pipes, boiler or anything else.

The Cylinder company have replaced the cylinder with a brand new one on two occasions, in addition to fitting air vents and swapping the return flow pipes.

There is no air in the system, system pressure is 1.5 as recommended.

They now seem out of ideas as we all are.

Interestingly the noise stops when you apply pressure to the return pipe...

Attached are some photos of the cylinder itself. Does anyone have any suggestions on what is causing the buzzing/humming noise?

 

[Johntheo5]

Is the coil HW entering through the top and returning via the bottom?

What is the boiler temperature when heating the cylinder?

Is there a (red) wheel (gate) valve on the coil return for balancing.

Is the air vent (AAV) on the return pipe open?

Is there a air vent (AAV) on the flow (top) pipe.

What do you mean by applying pressure to the return pipe?

Any noise when heating the cylinder with the electric immersion?

 

[Madrab]

What else is on that return pipe, valve/pump/etc? Sounds like you might have a sympathetic vibration and it's resonating down the unsupported pipe into the void below that's acting as an amplifier. If it stops when you hold the pipe then can you not use rubber lined munson rings on threaded bar and lock the pipe down onto the floor?

 

[terryplumb]

If you switch off boiler ,and heat the cylinder by immersion heater do you still hear the noise ?