Potterton Puma needs high flow to produce hot water

[tengri]

CH works fine and HW is OK too when it works but you need to open taps almost fully to get the boiler to kick in.

Keep getting tempted to replace the boiler but I've had a new one in the business premises which is not a great deal more reliable than this 20+ yr old Puma that is usually easier to fix.

 

[bazdaman]

Check the pin is activating microswitch cleanly on water assembly my guess is the diaphragm has gone or the pin is stiff.

 

[tengri]

Are they user serviceable or better just to replace?

 

[Gasguru]

You can often unscrew the brass bush assembly on the end and re-grease (silicon grease) the transparent pin etc. Isolate the cold first though.

Or may just need the microswitch turning in a turn or two.

Diaphragms seem to go on forever in these but may have perforated.