Alpha CB24 Combi boiler

[eccoboy1974]

Hi folks, I have an Alpha CB24 combi boiler on which I and my Corgi registered plumber friend could use some advice. The CH is working fine however, the HW is not. The boiler fails to respond to any demand from the HW tap. We have replaced the DHW sensor but to no avail.

Any help or advice is extremely welcome.

Many thanks, Ben

 

[HarrogateGas]

Try the diapragm.

 

[Agile]

Something that always interests me, can you tell me why your CORGI plumber friend does not ask the question here himself?

What does he say is the fault? I presume the "DHW sensor" he has changed is the DHW NTC sensor resistor ? Does he normally manage to repair combis successfully?

I have seen parts replaced by people who do not understand boilers very well and they sometimes put them in backwards or fail to properly connect the plugs.

Following Chris's forthcoming advice I have edited to enable me to suggest you look to see if the diverter valve pin is moving out and operating the microswitch when a hot tap is turned on. If not then either its jammed or the diaphragm has failed.

Tony

PS I am not quite sure what a "diapragm" ( sic ) might be but I dont think there is one inside this model.

 

[ChrisR]

Maybe no diapragm but it has got a diaphragm.
It also has a flow switch, which could be your problem too. It clips over the middle of the diverter valve, and relies on the diaphragm for the part it's in contact with to move, so either could be faulty.
Suggest you have a look at the manual??! Parts 100 and 142. On their website.

 

[eccoboy1974]

Thanks Chris and Agile for your repsonses on this one, my gas fitting friend is not one for using computers although I am sure he and many other people would benefit from using forums such as this one. The reason for the initial question was because he thought that it would be the diaphragm and had already changed it - (apologies, forgot to mention this in my initial post). The flow switch that clips on is also in working order and fires up the boiler when removed from its position - hey presto - hot water.

Am I correct in thinking that the only possible thing that could prevent the operation of the switch now is the pin - somehow stuck in its barrel?

Cheers BB

 

[Agile]

When changing the diaphragm he should have checked the rest of the diverter valve to ensure all the parts are free.

Do you see anything moving when you turn on hot water?

Tony

 

[eccoboy1974]

Hi Tony, I'm sure that it isn't the correct way to fix it, but I have just given the barrel section a few light taps with the back of the wrench and it has fired into life. I can now hear the flow switch click and the boiler fires up every time I turn on the hot water tap.

It seems to be working fine (for the moment at least) If it does go down again I'll have the whole section stripped down and cleaned and checked thoroughly as it does appear that the pin may well have been seized up.

Thank you for all your help sir, it really is appreciated.

Cheers Ben