Intermittent hot water fault on my Potterton Performa 28

[arfudge]

Hi,

I moved into my house a year ago and until 2 weeks ago have had no problems with my potterton performa 28 boiler. i fitted a digital timer about 5 months ago and that works fine. i believe the boiler is around 5 years old.

The heating works fine, however over the last two weeks the hot water has been intermittent.

Sometimes the water will start hot then go cold, sometimes i cant get any hot water at all, and sometimes the hot water works normally.

There is no pattern or regularity to when or how the hot water works. I mean, one day i might be able to get the water to run hot by turning the switch to CH&DHW and by turning the heating off. If i tried these same settings the next day the water would run cold.
The burner always comes on (even when the water runs cold) and there are no flashing LEDs indicating a fault.

I have put in a new DHW temp sensor and the problem still remains.
Both pins on the diverter valve assembly pop out and operate the microswitches and retract without sticking.

Does anyone have any ideas?

Thanks in advance

Andrew

 

[gas4you]

Check the flow pipe under the boiler. Could be DV sticking randomly in the cH position.

If flow gets hot when HW is called for that will be your answer.

 

[sus]

Diverter valve needs changing.
when you take the white cover off in the left hand corner you will have a brass assembly. In the middle of the brass assembly there is a piston when you turn on the hot water the piston should move it is probably not protruding enough to engage the microswitch in front of the piston. While you are having the diverter valve changed. Have the system serviced and have the plate heat exchanger de-scaled

 

[arfudge]

Thank you for your quick replies Sus and gas4you, I'll have a look at the diverter valve and its pistons and the flow pipe when i get home from work this evening.