intermitent hot warter biasi m90f 24s

[elansear]

Hi thanks in advance.
Biasi garda M90F.24S i am experencing increasingley intermitent d.h.w.
with the C.H. on and running every time D.H.W. is called for there is no problem, the diverter valve operates the burner continues to run and i get D.H.W. when the tap is turned off the burner still runs the diverter valve changes over ok. also the D.H.W.flow switch LED lights every time a tap is opened weather or not the C.H. is running. With the C.H. off and the D.H.W. fails to heat the ignision sequence starts, the pump runs the flow switch LED is on but the fan fails to run the boiler dose not light the pump then shuts down the flow switch LED is on and the operation LED indicates a fault (fail of ignition). when the tap is closed this LED returns to normal
also when it indicates a fault none of the other fault LEDs ore on ie no permenent fault condition. So could it be eigther of the 2 P.C.B.s or something cheaper, hopefully, the boiler was installed new in april 2003.
If its any help the D.H.W. supply is via a water softner so should not be a chalking problem. THANKS

 

[Agile]

I expect the system flow switch is not operating reliably. Probably as a result of a partially clogged plate heat exchanger.

Read the two current threads on an Ideal S28 for a list of the possible causes if you expect to want to try to fix it yourself.

Otherwise find a good boiler engineer!

Tony