hot water on combination boilers work in the way of how much the boiler can increase the temperature of the cold water coming in to the appliance at a certain flow rate. usually a rise approx 40 degrees celsius at 8 litres per min or a rise of 35 degrees celsius at 10 litres per min. Example : if cold water temp coming is 10 degrees, then you should get approx 50 degrees+ at approx 8 litres per min. However, this time of year mains cold water temperatures can drop to as low as 2 degrees and can affect hot water temperaures on combination boilers !
Curtis Lee Patrick
February 2008