Hi, I have a BIASI M96.28SM/C boiler. Any time we use hot water it makes a banging noise during the time water is used. When the central heating comes on at first in the day, the boiler makes the same banging noise for a few minutes, then it goes away - you never hear it again until the next time the central heating starts from cold. I have changed the D.H.W heat exchanger but this did not cure it. If anyone has suggestions for remedying this problem, it would be greatly appreciated. Many thanks,