Baxi duo-tec 40HE squealing when DHW & CH used together

[Bicko]

Hi all,

I have a squealing boiler issue that seems different to the norm, well I can't find any similar posts regarding this!

When CH is on and hot water is demanded, by opening a tap (any HW tap), there is a loud squeal or whistle given off by the boiler. The squealing used to stop after a few seconds, but now continues until the hot water is no longer demanded.

This doesn't happen when CH is off.

It only happens when both Central Heating AND Hot Water are required at the same time.

Not wishing to lead you down a particular path, but I suspect the diverter valve - purely because it is the component that is responsible for switching from CH to DHW (and back) in this situation.

With the cover off the boiler, the noise *seems* to come from the diverter but it's very difficult to tell really.

I've taken the motor off the top of the diverter and pressed the pin up and down a few times - it seems free enough, but I've nothing to compare it with.

Does my reasoning seem sound to you experienced people?
Is a change of diverter required?
What else could it be?

I'd be grateful for any advice, please.

Many thanks,
Mike.

 

[Agile]

I dont like plastic parts in boilers!

Often rubber seals if stretched can squeal but your senario is unusual.

Perhaps some of the engineers who work for the manufacturers can say they have encountered this noise?

Tony

 

[Bicko]

...Perhaps some of the engineers who work for the manufacturers can say they have encountered this noise?...

I hope so. Thanks for your reply, Tony.

I can't imagine that I've stumped everyone with this issue... ideas, anybody?

Thanks,
Mike.

 

[Homesafe]

When hot water is demanded the boiler fires up on high flame to heat up the very cold water going through your pipes, your problem could be a scaled or part blocked heat exchanger, which could mean dirty system amongst other reasons.

 

[Bicko]

When hot water is demanded the boiler fires up on high flame to heat up the very cold water going through your pipes, your problem could be a scaled or part blocked heat exchanger, which could mean dirty system amongst other reasons.

Hi Newgas, thanks for your reply.

My noise problem only happens when hot water AND central heating are demanded at the same time. If the heating isn't on, hot water is delivered without any noise at all. Does that rule out the heat exchanger?

Thanks again,
Mike.