Main combi 24HE wont turn off.

[Olivias Grumpy]

Hi

I had a complete diverter valve and diaphragm assembly changed a month ago, due to poor DHW at upstairs bathroom.
At same time my plumber remover plate heat exchanger for cleaning. When it was removed he found some plastic debris and a spring located in the entry port of the DHW side of the exchanger.
He looked in the manual and the spring looked like it had come from the Venturi.

He removed the venturi from the inlet assembly, and sure enough the venturi was broken.
New venturi obtained and fitted.
Boiler re-assembled and all worked well. Good result.
Woke up this morning about 3am. and i could hear the boiler firing and shutting off.
Turned mains off .

Quick look today showed that the DHW diapraghm is just touching the microswitch and therefore boiler fires etc.
No taps are open so the diaphragm should be at its mid point??
i can push the diaphragm push rod back, but it slowly drifts back out and starts the sequence again.

I understand the principle of how the diapraghm senses a differential pressure when tap opened.
But what causes a differential pressure if taps are closed and there is no flow through the boiler.

This happens with the heating circuit switched off.

In the Main Manual that is with the boiler the diagram on page 8 refers to item 9 Flow Sensor with Filter . I can see that the diapraghm pressure sensing positions are located here.

But what is 9 Flow Sensor with Filter ? Cant see a ref to it in the parts list at the end of the manual.

My plumber is now recovering after having a new knee fitted, so he cant attend for a while.

Any advice would be appreciated.

Thanks

 

[picasso]

First thought is you have a leak on the hot water pipework, do you have pipes running underground ?

 

[gas112]

ditto Turn off the cold valve under boiler if it stops you have a leak on the hot

 

[Olivias Grumpy]

Hi Chaps

many thanks for very quick responses.

Im back in work this evening so i will check when i get home.

i havent seen any obvious signs of leaks anywhere in bathroom or kitchen. No drips from ceilings etc.

However i will shut off the cold feed and keep a watch on diverter rod.

Cheers

 

[Olivias Grumpy]

Sorry all, never did confirm problem
The New diverter was faulty or rather the diaphragm section.

The pin operates the micro switch had broken out of its plastic disc inside the diaphragm housing.

Old diaphragm module fitted and no further problems

All is good 5 months later