i have a response 120 boiler which over this year has practically been rebuilt. the problem i have at the moment is that when demanding hot water the boiler does not fire, when demanding heating the boiler fires up then shuts down after about 12 seconds. last week i had the heat exchanger tank and ignitors replaced as tank had burst. the pressure is round about 1.5 bar and steady. the pump was replaced last year. the boiler is about 4-5 years old. i am a loss as are scotish gas to the problem. has anybody had a similar fault and had it rectified? again this is an intermittent fault so one day it is ok the next it wont work at all. one other observation is that the hot water flow rate from the tap is higher than what it was before as it was not heating the water due to the flow. any ideas or answer appreciated