Our company consists of a partnership of a number of self-employed people, plumbers, breakdown technicians and various other disciplines.
Disruptions
I use Vaillant's GSZ method when troubleshooting problems. (Structured Fault Search).
This method was originally used by Defense, and is generally applicable to mechanical installations.
Each installation is divided into device tasks, sub-tasks and preconditions. An analysis of the fault is then made. The advantage of this method is that the device is independent. It is determined which device task is failing, then the matching specific component is examined.
Central heating boiler
A central heating boiler is composed of a (limited) number of separate parts. Contrary to popular belief, a malfunction does not necessarily mean that the boiler is reaching its end.
A pump may fail, but the rest of the boiler may still be fine. One part is separate from the other. The only need for replacing a boiler is excessive gas consumption or insufficient heating capacity.