i could be wrong but all combis are designed to supply a set flow of water at a set temperature if you turn the tap on too much you exceed the flow rate and the water won't reach the set temperature (especially in winter) so turn the tap on and WAIT until the temperature stabilises if it's too cold turn the tap off slightly and WAIT until the temperature stabilises the secret is in the waiting i've lost count of faulty boilers i have "repaired" this way
brian
December 2010