Alpha CB24 Combination boiler

[Perry61]

My Alpha CB24 will only produce hot water (DHW) when the central heating is running (CH). I have followed the fault finding flow chart and so far have replaced, DHW flow switch, DHW flow valve diaphragm (it was worn and had a small hole in it) and the DHW heat exchanger with no improvement. Any ideas?
Also if I unseat/lift the DHW flow switch by just a couple of millimeters the boiler fires up for DHW.

 

[sandybeach]

If the hot water flow switch is making and breaking when you open and close the tap, then go to section L on page 32 of the manuafacturers instructions and follow the instruction regarding checking for dc voltage on the pcb.

If you had followed the fault finding guide correctly rather than throw parts in to the boiler you might have saved a coin or two.

 

[sandybeach]

If the boiler fires when you lift the switch then you've not fitted the diaphragm correctly or the spindle in the divertor valve isn't moving.

Replace the whole divertor valve assembly.

 

[Perry61]

Thanks for replying.
My manual does not have a K or L it stops at J, I have just downloaded a copy with the additional solutions.
My thought was that, as the boiler fires up if I lift the DHW flow switch the PCB was working.
Thanks

 

[Agile]

I would normally replace the whole diverter valve for a customer.

Tony

 

[Perry61]

Gents, I refitted the diaphragm in case it was not seated correctly, I couldn't tell if it was but I took extra care when I reassembled, but I have not been able to test it as I have a leak on the bottom of the diverter valve under the DHW switch. I did not touch this as I took the pump out to get to the diaphragm. Am I stuck until I replace the diverter valve?

 

[Perry61]

Gents, re did it all again, no leaks and so far it's working as normal.
Thanks for your help.

 

[tdz840]

If the hot water flow switch is making and breaking when you open and close the tap, then go to section L on page 32 of the manuafacturers instructions and follow the instruction regarding checking for dc voltage on the pcb.

If you had followed the fault finding guide correctly rather than throw parts in to the boiler you might have saved a coin or two.

Hi I read the FF checks for checking for dc voltage at pcb.
The connections 16 and 20 should have a dc voltage (cant remember without checking the manual). However as it is a plug with no connection ican put my multimeter to how is this done?
I looked at the back of the pcb and there is a blob of solder for each of the connections that i could read from but they are awfiully close to the corresponding connection and was worried about making a short and frying the board.
Any help?
Russ

 

[DP]

Replace the whole divertor valve assembly.

I have never replaced the diverter- always service them. Carry diaphragm kits for these.

 

[prezzie]

thermostatic shower running hot then cold, when shower turned on the flow is not enough and thus the boiler temperature gets to high and cuts off only cool enough to re-light, bearing in mind this boiler apart from the DHW switch has been good for 9 years, so i after reading many posts on this site decided to change the the diverter diaphram, first removed the heat exchanger then the whole diverter valve comes out ok, i could have just removed the pump to fit the diaphram but so glad i never, when i pulled the valve apart i was glad to see a rip in the diaphram, but the rest of the valve was full of hard black gungy stuff stopping the valve from full diverting, so as a cautionary tale changing the diapharm only may not be a good idea, after all was scraped clean and exchanger flushed out little bit of silicon grease in places all is now working fine, i can see were the recomendations are to fit a brand new complete diverter valve but thought i,d risk a diaphragm kit for around a tenner,

hope this has been of some help to people