my i-mini 24,30 comby boiler has a problem

[dellseymour]

Hi, my names Dell from Nazeing near Harlow, my i-mini 24,30 combo boiler works fine heating the ch,
also heats the water but only Luke warm, ive got the control knob turned to max.
any ideas what the problem could be?

 

[Dotty]

Yep.

You need a gsr in to fix it though.