Hi I have a vokera excell e80 combi boiler and no hot water
works hot water when central heating is on .

Central heating fine , it sopunds to me as if I have the same problem that the domestic daiphragm could have a hole in it

I have the user and service manuals but none give a good picture of the part . I also have the part # and is it ISC # ?

Anyway the part is less than £10 can I fit this myself or is it too dangerous and I should call out an engineer .
The instructions on how to above sound relatively straightforward any advice would be great

Iain , Glas, July 2008

If the fulcrum arm is moving full travel then the micros switch may be on its way out. They do sometimes break & get stuck, either in permanent demand (your boiler will be on all the time) or off (no hot water unless CH on).

c, July 2008

Having never looked inside a combi boiler I was impressed that this information took me straight to the source of the problem.

I could see that the small piston was pushing out when the hot tap was turned on. It takes about 3-4 seconds to fully expand so I don't know if this is normal.

The microswitch works fine. By operating this manually the boiler fires up.

What was at fault was that the piston wasn't pushing the microswitch enough to activate it.

A little adjustment by bending the microswitch arm got it going again.

Is it likely that the diaphragm is nearing the end of its life anyway?

Andrew Vevers, July 2008

It is not dangerous if the electricity supply is switched off and you have a modicum of common sense. You dont have to touch anything gas or flue related. When you replace the diaphragm make sure you clean every scrap of old perished diaphragm from the brass insides and the plastic pusher piston; it will last months instead of years if you don't do this.
Dont forget to turn off the DHW cold supply before you start work!.

c, July 2008