Potterton suprima40 boiler guts

[Tris]

I am inspecting inside my boiler, and am intrigued by the following:
there is a rubber pipe leading from inside the fan-box, out to the electronics compartment on the boiler. It connects to what looks like a diaphragm module. there are electronic connections to this diaphragm module. there is then another (pink) pipe leading from the diaphragm and terminates open inside the space in the main boiler.
what is this subsystem?

 

[MANDATE]

What you are looking at is the 'air pressure switch assembley.
The fan creates a vacuum through the plastic tube and pulls on the diaphram, When the diaphram moves it releases the pressure from a spring loaded micro switch.
You will see two wires ( orange I think they are) going to/coming from the micro switch, the contacts when properly wired are normally open preventing boiler from operating, when system is switched on the fan runs and switch is made before the boiler flashs up.
The micro switch does have a third terminal covered with insulator which is not used.
I have run my fan from an independant supply to prove the micro switch was operating correctly

 

[breezer]

DID YOU KNOW? a washing m/c has one too. (except it works by air pressure not air vacuum)

it tells the fill valve when to stop because it has enough water. they can have more than 1 "level" which is usually only used if the "wool" programme is selected as wool needs more water, so the m/c fills more

useless but true

 

[ChrisR]

Yes!

 

[Tris]

OK, I think I was onto that actually when I found the PCB connections diagram inside the shell. thanks a lot for confirming though! I certainly did not know about the wsahing-machine application though.