Ravenheat 820/20T Problem with Slow Ignition Sequence?

[splosh]

I have a Ravenheat 820/20T which has developed a problem with its ignition.

If the boiler hasn't been used and is cold then it ignites correcty within 5 to 10 seconds of central heating or hot water demand.

However after using the hot water for a bath or shower, the boiler will not re-ignite on demand for up to 90 seconds. Even if I over ride to cenral heating mode, it can still take a very long time.

I have recently replaced the diaphragm in the Gianonni 3 way valve and I can hear the microswitches operating correctly.

Has anyone got any ideas?

 

[Agile]

It sounds to me as if it may be a problem with the fan/venturi/APS but it could be other things as well.

However, those aspects have gas safety implications so should be done by a competent person mormally CORGI registered.

Tony