Potterton Puma 80 DHW delay

[ratterjohn]

Hi. Apologies if I'm covering old ground, but I could not see the same problem.
So Potterton Puma 80 perm. pilot CH works fine, but DHW takes 5 mins to kick in, occasionally much longer, and sometimes quicker, and it is fine when it does start, but just a bit of a pain.
Just wondering if the DHW expansion vessel could cause this, or flow switch, or diverter valve?
No idea really, so any help would be appreciated.
Thanks.

 

[powell30]

pressure diff maybe split. When you turn on tap does the microswitch make on the pressure diff?

If not change it

 

[ratterjohn]

Thanks for reply
"does the microswitch make on the pressure diff"?
The red light on pcb comes on and off with hot water demand if that is what you mean, or should I be looking for something else.

 

[Baxmax]

Air Pressure Tube split/loose/fell off at fan venturi.All rgi stuff though.

 

[ratterjohn]

Thanks. I'd just like to rule out a few things before I call anyone out. I'll have another look in daylight.

 

[twgas]

ruling out a few things is all well and good but any breakdown engineer would check the basics and work through so any "bits are ok" don't mean anything.