Vailant turbomax plus makes noise when on DHW

[dmbuk]

Hello

The boiler is Vaillant turbomax plus 824e, CH works fine.

If one hot water tap is open, the boiler works normal too.
However, when the second hot water tap or shower on its own is turned on, the boiler starts making noise that gradually gets louder until I shut the boiler down.
Could be a heat plate exchange? No error faults shown. The boiler was shut for around 10 months (the property was empty). CH pressure topped up to normal.

The noise can be heard at the end of the video after I opened the second tap.
Any advice appreciated, many thanks!
Dmitry.

 

[CBW]

Sounds like a blocked main heat exchanger.

 

[dmbuk]

Thanks Chris, why would it work fine on CH? sorry for may be lame question, I am only google qualified man
A gas engineer came to service the boiler recently discovered the issue and immediately retreated with "you need to buy a new one".
Which doesn't make sense to me as the boiler looks good and clean inside, and partly works.

 

[CBW]

When the boiler is working in hot water mode, the burner is on full and the water is being circulated at a higher rate than in central heating. What I have noticed is the pressure is low on your boiler too.

 

[dmbuk]

When the boiler is working in hot water mode, the burner is on full and the water is being circulated at a higher rate than in central heating. What I have noticed is the pressure is low on your boiler too.

good point Chris.
The pressure was topped up to 1 bar, before the issue was discovered.
I've got the tools, it is possible to DIY replace the heat plate exchange?

 

[CBW]

I've got the tools, it is possible to DIY replace the heat plate exchange?

That would depend on competence and the ability to carry out 26.9 of the gas regulations and have a FGA.