I have a combi boiler system prob. Our hot water comes out lukewarm, though our heating is fine. Any ideas?

robryan seems to be on the ball, another thing to check is your hot water diaphram as they stretch and sometimes dosent push the microswitch fully open, think your best bet is to call an engineer, depending on what make of boiler you have its cheaper to call out the manufacturer, eg worcester charge about �90 per call out inclusive of parts