Vokera Excell 80SP - intermittent warm/cold through hot tap

[Merstone]

I have a Vokera Excell 80SP boiler and the only way I can get hot water is to only have the tap open a small amount. If I open up the tap less than half way I only get warm or intermittent warm/cold water, as too much cold water is being let through.

Can you advise me as to the most likely reason for this? Seems like something might need cleaning/replacing to increase the hot water flow but I would appreciate any advice.

Thanks

 

[twgas]

plate heat exchanger most likely

 

[Merstone]

Thanks. Can the heat exchanger be easily cleaned and if so, how?

 

[twgas]

not done one on your particular boiler but its not usually the easiest job in the world, I normally replace them, but the system will have loads of muck aswell so a good flush, inhibitor and a magnaclean will be a good bet.

 

[Rob]

Would check to see the diverter valve isnt letting by first. With heating off/cold feel the heating pipes underneath the boiler when the HW is on. They should remain cold.

 

[DP]

If the diverter was letting by to CH, I think burner would not go out. My vote would be clean the system, inhibit and then (if needed) replace the HWHE.

I have used DS40. It sometimes does clear the system and HWHE (unless you have plastic pipe)