Not hot water but rads fine

[hertsman]

Hi,

I have a Potterton combi. It's heating up rads fine, but there is no hot water. Is there a simple explanation, or something I can try?

I also notice there is a knocking noise when the system comes on/off. It's been doing this for a few weeks so I don't think it's caused the hot water problem. Again, is there a simple explanation for this?

Thanks

 

[Agile]

Potterton have made a lot of different combis.

No DHW is often as a result of a failed diverter valve ( when fitted ).

Tony

 

[hertsman]

It's a Performa 28i.

After a minute or so, the green hot water light flashed then went off again. WIll the whole boiler need replacing, or just a part?

Thanks