d.w.c. working but no c.h

[jonny555]

hi everybody.

i'm having problems with my boiler.
biasi riva compact m90e.24s
the problem is the c.h. when switched on
wheather on constant or through the timer
it kicks in for about 30sec then trips out leaving the
green light flashing fast. the d.h.w. is working fine and
if i leave a tap running while having c.h. switched on
when the tap is closed the c.h. sometimes carrys on and is fine.

this has now been going on for almost a week.
what i'm looking for is wheather its worth spending
on this boiler as i've read, not the best.

many thanks..............

 

[Goodman]

Hi,If you have a service manual look in pages 26/27 fig.60/61 replace diaphragm(membrane) at the same time i would replace one on dhw diverter valve as well.

 

[Agile]

Goodman, I think that you have not properly read this posting! This is an M90 and NOT a 24S.

There is not a diverter valve membrane! Its a motor driven diverter and the DHW water flow is sensed by a magnetic shuttle which activates a hall effect sensor.

The OP should observe the system flow switch and see if its being reliably activated on CH. My guess so far is that it might not be!

Tony Glazier

 

[ChrisR]

You may have to rotate the dhw flow switch towards you, to see its led coming on and going out correctlly

The primary flow switch pin near C should operate the microswitch in the case D

 

[jonny555]

hi there,

thanks for the replys,

i have checked the diverter valve and spindle
seems to be operating although makes quite a noise.

also the red light on the flow switch is visible when
d.h.w. is opened but nothing when the c.h. is switched on.

just to confirm the boiler is
biasi m90e.24s.

many thanks.

 

[jonny555]

goodman
mant thanks but your page no's and fig's
are not relating to my manual.

 

[Agile]

You say that you have "checked the diverter".

I doubt that you have!

Is the black motor actuator really driving the pin down in the CH mode? And returning to release the pin for DHW?

If not then measure the voltages on the connections to it and report what you find in each mode.

Tony