Alpha CB24 boiler hot water problems

[longestdrive]

Hi
The hot water on our CB24 boiler stopped working under any circustances.

I've just replaced the diverter diaphragm - which when I removed had a hole in it, flushed out the secondary heat exchange and replaced the dhw switch.

Now, the hot water is working only if I set the tap to about 1/2 flow, if I set it higher the water goes cold. It's as if the boiler can't cope with the full flow?

Central heating works fine. Water gets hotter if the heating is on

The new diaphragm had a slightly bent pin so I straightened it as much as I could before fitting.

Should I now consider replacing the diverter valve itself?

Not sure what my next step is here. Can anyone point me in the right direction

 

[Agile]

Where did you get the diaphragm from exactly?

How sure are you that you put it the right way round and what about the spring?

Tony

 

[ianmcd]

when your boiler was installed it is more than likely that your installer regulated the flow rate of your DHW to give you a proper temp rise but as you have turned this off to replace the DHW diaphragm them opened it back up ,I suspect you have increased the DHW flow rate to more than the boiler can produce, you need to measure what the flow rate you have , find a container that you know the volume of and measure the time to fill it, I.e. say its a 10L container and it takes 1 minute to fill then you have a flow rate of 10L/min you get the idea, most combis are around 10L/min to 13L/min as a rough guide if you have a lot more than that then that is your problem would need boiler make and model to be specific

 

[Agile]

I had interpreted what he said as boiler ceases to fire!

If he really meant that it just went less hot then he has used a poor choice of words!

Tony

 

[longestdrive]

Hi

I bought the spare parts of ebay.

The diaphragm was I believe fitted the right way rounf - I noted the original installation with the spring mechanism pointing to the right and the larger spring on top of that again to the right, contained by the cover.

The boiler fires up every time the hot tap is turned on, ignition is working as expected.

If the central heating is on the water is noticeably hotter than when the heating is not on. Either scenario though if I turn it fully on the water turns cold. About half on (flow from tap) is acheiving best results so far.

The boiler hot tap used to be fine until it stopped so I think the boiler is/was up to it.

Just not sure what my next step is - should I get another diaphragm incase the pin is causing an issue - maybe not 100% straight?

Assuming the pin is pulled back into the housing to trigger the switch then that seems to work ok but if it's not retrieving enough (say pin snagging) does that affect ability to heat dependant on flow??

 

[longestdrive]

when your boiler was installed it is more than likely that your installer regulated the flow rate of your DHW to give you a proper temp rise but as you have turned this off to replace the DHW diaphragm them opened it back up ,I suspect you have increased the DHW flow rate to more than the boiler can produce, you need to measure what the flow rate you have , find a container that you know the volume of and measure the time to fill it, I.e. say its a 10L container and it takes 1 minute to fill then you have a flow rate of 10L/min you get the idea, most combis are around 10L/min to 13L/min as a rough guide if you have a lot more than that then that is your problem would need boiler make and model to be specific

I'll check this. I was worried about how far out to turn this screw - In installation it said antic clockwise to increase temperature

My boiler is an Apha CB24

 

[algas]

when you are running the hot water does the c/h flow pipe get warm? if so the diverter valve is stuck.

 

[longestdrive]

when you are running the hot water does the c/h flow pipe get warm? if so the diverter valve is stuck.

Yes the CH was warm - just finished stripping down the diverter valve, cleaned up the valve inside, also took apart the diaphragm and re-used the old pin in the new diaphragm

NOw have hot running water with tap fully on!

Assumed sticking valve

Thanks