Can someone help me please!! I have a worcester bosch 280 rsf combi boiler and I am having snags with the domestic hot water, when the tap has been running for a short while the water in the boiler sounds as if its boiling and the gas cuts off, then after a while it re-ingnites and continues the same cycle. I have checked the hot water temp sensor on the outlet and it is clean and not scaled up, could there be air in the boiler system or another problem. also are there any bleed points on the boiler itself?