Alpha CB24 BIG !! problem

[pigley]

Problems startd off with shower not working properly - water started hot then went cold, came back hot and continued like this - most inconvenient to keep hopping in and out with soap in my eyes ! This was an intermittent problem because sometimes the hot water was fine.
Plumber replaced top temperature sensor.
Did not solve problem.

Then central heating started to play up - kept switching itself off but came back on when all radiators had gone cold. I have TRVs fitted on all rads except for 2 (one in bathroom and one on landing). When boiler cuts out - sometimes both red and yellow lights are on continuously, at other times the yellow light flashes on every second. Could not reset boiler until it had gone cold. Same problem as above with hot water.
Plumber replaced diverter valve. Seemed to be ok for 24 hours but.....
Did not solve problem.

Now back to square one. Hot water sometimes comes on, sometimes it doesn't and sometimes it goes hot and cold. Central heating comes on, sometimes stays on for an hour goes off and resets itself, sometimes it stays on for longer.

Plumber coming back on Monday - any suggestions would be gratefully received - we need help. If you can't offer advice then please just pray for a warm weekend for me - but maybe not too warm if I can't have a shower!.

 

[ChrisR]

Wait for Paul, and hope it isn't the nearly £300 pcb...

 

[pigley]

Hope it isn't £300 as I have already paid £293 for the diverter valve !

 

[Paul Barker]

sometimes both red and yellow lights are on continuously,

Odd there is no fault code for that, but A (red light) continuous is flue or fan fault (which means blow out sense tube, sometimes even remove fan hood and physically check for a moth's wing in it), and B (yellow) continuos means boiler is lit and working.

at other times the yellow light flashes on every second.

Temperature sensor fault.

Could not reset boiler until it had gone cold. Same problem as above with hot water.

as above?

Plumber replaced diverter valve. Seemed to be ok for 24 hours but.....
Did not solve problem.

not surprising, as it's a whole system fault

Now back to square one. Hot water sometimes comes on, sometimes it doesn't and sometimes it goes hot and cold. Central heating comes on, sometimes stays on for an hour goes off and resets itself, sometimes it stays on for longer.

I too would have changed top ntc, is the new one white? I would also be checking the flue for obstructions the sense tube the fan and the aps.

pcb's very reliable but yes as I carry the stock I would certainly have to try it in your circumstances to see if the behaviour improves after I had double checked everything relating to the fan, and the leeds from the ntc to the pcb, but probably not until I had changed the ntc again, though they are now ultra reliable it is always possible to fit a duff replacement. One of your fault codes points to it, if replacement is blue it's old stock get a white one fitted.

Not a range of behaviours I have experienced.

 

[pigley]

Many thanks for your help, Paul Barker.

Turned out that a faulty (white) temperature sensor had been fitted at the start of the problems.

 

[Paul Barker]

Wow that's a big surprise I haven't had a single white ntc failure.