some boilers are not big enough to supply a shower in winter i suspect that yours is only 24kW output you may be able to improve the showers performance i.e. restricting and or reducing pressure of the cold supply to the shower but you may need a plumber to do this
brian
January 2011
Automatic Answer
We may have found other answers which could help you.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix home heating systems.