My six month old Optomax HE 31 C boiler was working perfectly until 3 weeks ago firstly the pressure started to drop got the engineer out nothing wrong with the boiler radiator valve leak so I fixed that. Then the water started going hot then cold got the engineer again, heat exchanger leaking got a new heat exchanger but still no hot water just luke warm this is apparently because water in the radiator pipes is dirty can this be, the digital read out is set 55 degrees but when I turn the water on it gets up to 40 then drops down to 30 then back up all in a space of about 30 seconds and I sounds like a 30 old boiler. Can anybody give advise before I get miserable looking engineer out again.

Cold Cumbrian, February 2008

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