Occasionally a system will become restricted by sludge and even the best boiler will not be able to cope. Sometimes there will also be cold spots on radiators or your boiler might even overheat. A powerflush is a process of coupling a large pump in place of the system pump and together with powerful chemicals, breaking down the deposits of sludge and removing them from the system.
I have done many, many flushes over the years, and your system will work more efficiently if it is clean.