Humming Heating

[mogget]

I have a weird problem with my own heating system which I'm at a loss as to how to cure.

Boiler: Vaillant 418; Pump: Grundfos 15/60 on speed 3; System plan S-plan+

The problem is a gentle (but clearly audible) humming sound which comes and goes. This is a new problem in the last few weeks and it seems to be getting louder.

The noise is not combustion related - if i turn down the boiler stat the gas valve clunks shut but the noise continues.

If I turn the system off the noise stops as soon as the motorised valve closes and it goes onto pump overrun through the ABV.

If I turn the pump to speed 2 the noise stops but then the boiler decides it doesn't like me (doesn't modulate properly and goes onto short cycle).

All pipes are securely clipped and the system is (very) clean.

Anyone have any ideas before I swap out the pump?

Thanks

Mogget.

 

[scoobydo123]

I have had similar with a pump going noisy. It seemed to be working fine but hummed. Obviously when MV are closed then pressure differentials could be different and your problem goes away. Mine was noisy all the time. You could try cracking the pump nuts and rotating around its axis this may help.

For mine I changed the circulator only because I had a spare one from another installation and peace and quiet was resumed.

 

[mogget]

Mine was noisy all the time. You could try cracking the pump nuts and rotating around its axis this may help.

Hi scoobydo

The funny thing is, the noise is only present on the main house zone. When it's on hot water or the kitchen zone it's fine.

Unfortunately the pump axis is vertical so I don't think that will help.

I might just have to bite the bullet and put on a spare pump.

 

[mogget]

I might just have to bite the bullet and put on a spare pump.

I've had a look and feel around the heating cupboard and I now suspect my cheap and nasty ABV is the cause. Back it off - noise stops. Close it completely - noise stops. Anyone heard of a buzzing ABV before?

EDIT: Or indeed, any recommendations of a good replacement?

 

[mogget]

I'm talking to myself again, I know, but for the benefit of anyone visiting the forum in the future, it was indeed the auto bypass valve.

I've just replaced it with a new Danfoss one and the heating is quiet again. Peace at last!

 

[scoobydo123]

I will remember that one for sure so not wasted