Water only hot when heating is on!

[phykell]

Hi,

Had a Worcester 24CDi fitted recently to a 3 bed semi (with electric shower so no huge demands on hot water needed). The central heating runs just fine but the hot water only runs hot properly if the heating is on. If I run a hot water tap when the heating isn't on, although the boiler switches on and the lights indicate it's heating hot water, the output is only luke-warm even with the temperature controls set to maximum.

Thanks

 

[shaneo]

when u turn the tap on does the flow pipe below the boiler, going to the heating, get warm? if so probably the diverter valve

 

[phykell]

when u turn the tap on does the flow pipe below the boiler, going to the heating, get warm? if so probably the diverter valve

Just tried it! All the pipes are cold except for the hot water flow (2nd pipe in from the left) which is luke warm.

 

[MarkJayne]

I have a 24cdi, and had the same problem. My trouble was that it was the diaphram that had gone. Mine was 5 years old though.