hot water problem on a betacom 24c

[thelittleplumber]

when i turn on hot water boiler fires up for about 15 seconds the the demand light goes of and I get not hot water at all but if i turn the tap on very slowly and leave the water running at a very slow pace i get hot water anybody got any ideas is it possibly the secondary heat exchange unit blocked would appreciate any advice the boiler is a betacom 24c

 

[picasso]

I reckon your right, blocked secondary heat exchanger would fit the symptoms.

 

[thelittleplumber]

Thank you for the advice given thought I was right but I would rather be safe than sorry so once again thank you