Image via Wikipedia “Kettling” and “knocking” boilers are usually caused by hard water lime-scale and sludge deposit formations on the heat exchanger surface which causes the surface to become too hot, resulting

in localised boiling, irritating noises, low energy efficieny and ultimately, failure of the boiler unit itself. This type of problem affects all types of boiler whether oil-fired, LPG or natural gas.

Central Heating: Fault Finding and Repair
1) What Central Heating is
2) What can go wrong with it
3) How to diagnose the fault
4) How to repair it

Boilers and central heating: Fault Finding and Repair - more information

Tags: Boiler, Central heating, Heat exchanger, Heat transfer, Natural gas, Water heating