how to replace diaphragm on potterton performa 24 combi

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my combi has recently stopped producing hw. water flows, but the boiler doesn't fire up when i open a hw tap. however, the ch is fine!

it's been suggested that i probably need a new diaphragm and it looks like this will cost me about 200 quid to get fitted. however, i've searched other posts on here and it seems like this should (in theory at least) be a fairly simple job which i may be able to do myself.

as such, can anyone confirm if this is sth i can do myself - i have v little knowledge of boilers - and, if so, how exactly do i do it?

cheers.
 
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As this does not entail any disturbance of gas parts, safety devices or the removal of the combustion chamber cover then if you feel up to it, it is indeed a very simple job.

Isolate boiler electrics, remove dhw flow switch, isolate cold inlet under boiler,open a hot tap to remove any residual water pressure, undo the 2 small front small pipe on the top of the diaphragm cover, then slowly undo the screws holding on the diaphragm cover.

Put a small tray under the boiler and some tissue/small towel inside it, especially over the pcb cover.

As always, if you don't feel confident, get someone in, as it will cost a lot more if you cock up and then ask an RGI to come in :eek:
 
it's been suggested that i probably need a new diaphragm and it looks like this will cost me about 200 quid to get fitted. however, i've searched other posts on here and it seems like this should (in theory at least) be a fairly simple job which i may be able to do myself.

cheers.

Its a fairly simple job for a boiler engineer but then brain surgery is simple for a brain surgeon! As we have no idea of your capabilities its difficult for us to guess how you would fare.

I dont know where you got a price of £200 from!
Tony
 
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thanks guys, gasman1965 if by MI you mean the instruction manual then yes i do have it. however, looking at the general layout diagram, the diaphragm is not shown. i'm assuming it is part of the 3-way valve assembly. is that right?
 
ok, i think i have loacated the diaphragm chamber with this info found on the net:

The whole assembly is made up of two main brass sections: the first is the \"Pressure Differential Assembly\" (diaphragm chamber), identified by the six screws clamping the two parts together. Inside the chamber there is a flexible rubber diaphragm. The diaphragm is made from ethylene propylene WRAS (Water Research Advisory Service) or WRC (Water Research Council) approved rubber, specifically selected to comply with the UK water regulations.

so ultimately as i understand it i need to remove the two pressure pipes coming out of the top of the chamber and then open the chamber itself by removing the 6 screws on the front of it.

however, where is the dhw flow switch? is it the switch on the front of the chamber? If so, this switch does not seem to activate when i open a hot water tap either. is that due to the diaphragm or a seperate problem?
 
Yes its in the diverter valve mate .. Reason I asked if you have MI is it will help you find the part and has pics ;)

Its in the disc shaped part which is brass and a few screws hold the 2 parts together which is separated by the diaphragm !!

Follow the instructions in the MI for removal and refitting ..
 
Yes its in the diverter valve mate .. Reason I asked if you have MI is it will help you find the part and has pics ;)

Its in the disc shaped part which is brass and a few screws hold the 2 parts together which is separated by the diaphragm !!

Follow the instructions in the MI for removal and refitting ..

ok cheers, but what exactly is the "MI"? My "installation and servicing" instruction manual has nothing about the diaphragm in it. can i easily get my hands on this MI? thx again.
 
Manufacturers Instructions !!

Have you got the User Instructions or installation/servicing ?
 
Manufacturers Instructions !!

Have you got the User Instructions or installation/servicing ?

cheers, i've actually just found the section on the diverter valve assembly in my servicing manual. i guess that's as good as it gets ;)

final question: is the dhw switch what they call the "microswitch bracket" on front of the diverter valve assembly? this is not working at all at the moment. is this to be expected with a faulty diaphragm? also, is it this switch that causes the burner to ignite (which it doesn't at the mo)?
 
When you open the water the diaphragm pushes a pin out to engage the switch ,, when the diaphragm is split or has a hole then it cant do its job, hence not firing up ;)
 
When you open the water the diaphragm pushes a pin out to engage the switch ,, when the diaphragm is split or has a hole then it cant do its job, hence not firing up ;)

excellent thanks! it's now starting to become clear and i think i can give it a go. just as a test for the HW, is it safe to trigger the switch myself? that is, i won't kill myself if i touch it will i? ;)
 
Be careful if you do do it coz the wires to the micro switch are live at the end of the day :eek:
 

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