how to replace diaphragm on potterton performa 24 combi

[otherparty]

finally got hold of a replacement diaphragm, so i opened up the valve, and found that the old dia was punctured. put in the new one and problem solved - i now have HW!!

Can't thank u guys enough!

Cheers!

PS: It was indeed a 10-min job!

 

[GasMan1965]

 

[green991]

nice one.
where did you get that part from?
i have tried google

 

[Agile]

turn water off under boiler open hot tap 6 screws ONE PIPE at top strip out replace including gland nut that comes with diaphragm kit 10 mins max.

I did one today but there were EIGHT screws !

Even so I still only charged £94 inc which is less than half the £200 the OP was mentioning!

Tony

 

[namsag]

IF you count the 2 on front panel and one holding on the microswitch ,there is 9 screws. But whats a screw amongst friends.
Usually trouble

 

[otherparty]

nice one.
where did you get that part from?
i have tried google

this took me days to find:

http://www.interpartspares.co.uk/

Good luck!

 

[green991]

cheers mate, turns out my local stockist has them.

 

[Agile]

IF you count the 2 on front panel and one holding on the microswitch ,there is 9 screws. But whats a screw amongst friends.
Usually trouble

But there were eight holding the diaphragm unit together!

Tony

 

[phil49]

Did all the usual fault finding checks as in manual but instead of firing within 5-10 seconds, it was taking as long as five minutes before flue fan started and then firing. Changed diaphragm, air pressure switch and overheat thermostat - still not firing quickly. Began to think the recent strong winds had displaced flue ( bungalow roof mounted) resulting in a pressure problem but inspection showed it to be ok. Then the penny dropped! There are 2 diaphragms on this combi and as it is probably seven years old they both needed changing. Felt smug and smart that I had found problem and fitted new pressure differential diaphragm.
The old one looked shabby but it was not perforated which slightly surprised me as it contradicted my fault diagnosis. And guess what? No difference in response. Stripped it out again , and lo and behold, beneath the diaphragm is a circular plate with a central hole for the pressurised water to pass and push the diaphragm. Needless to say this was blocked and was quickly cleaned with a needle. The diaphragm now pushes the rod to activate the microswitch as soon as the system demands.