Noisy CH when hot water only

[andy.budgell]

Hi there plumbing experts!

I have a normal vented CH system, with indirect hot water heating etc, pump in airing cupboard trad boiler in garage etc.

The problem is that when the system is only demanding hot water, there is a lot of airy and pump noise coming from the airing cupboard, and my manual air vent just in front of the HW cylinder is continually collecting air 24/7.

When heating is demanding as well, the airy noise is only slight.
I have to admit to playing with the 'bypass' gate valve, and the other
gate valve on the return from the HW cylinder but I've no idea how much
they should be open.

I would appreciate any help or information as to what anyone thinks is the problem. Its been like it since I last refilled the system.

I also have a lot of 'pipe' noise like you can hear the pump from any pipe in the house. Could the pump bearings me going? Its a well old pump I think!

Andy

 

[brumylad]

did you put corrosion inhibitor in the system.

 

[andy.budgell]

I may have forgotten that actually. In fact I did! Does that make a huge difference to the noise etc then?
Should i completely redrain or can I drain a little and whack it into the header tank so that it circulates over time anyway?

 

[ChrisR]

Check it isn't sucking air or pumping over, in the loft.

 

[ivanov]

Andy, did you get your problem resolved?

unfortunately I don't have a solution for you but have the same problem so I was wondering if you find what was causing the noise?

Thanks

 

[croydoncorgi]

Check the gland nut on the stem of the pump isolator valve on the suction side of the pump and other nearby joints on the suction-side pipework. The air must be getting in somewhere and needs to be stopped. It'll kill your pump.

 

[andy.budgell]

Problem not resolved yet.
Theres a strange scum on the surface of the water in the header tank?
I'm fairly sure theres no overpumping, I can normally hear it when the pump stops, but I'll check for sure.
Also, another interesting feature is that the 'fine' bubbly noise only occurs when the boiler loop temperature is getting close to operating temp??
When the boiler stops heating, i.e. No demand from CH or HW, then the gushing noise gradually goes.

 

[ivanov]

It seems that I might have found a solution.

Following the advice of the previous post the only suspicious thing on the inlet site of my pump was the expansion vessel. I've pumped addition 5psi into to the air part of the EV and the "washing machine like" noise seemed to disappear straight away.

Andy from the sound of it you CH is not sealed hence no EV so I'm not sure if that will help cure your problem but I decided to posted anyway.

Thanks