94 Wiring Systems and Fault Finding For Installation Electricians On one occasion, the author installed the control wiring for a CH system, and was perplexed when the room thermostat operated the HW and the cylinder thermostat operated the CH. Much tearing of hair followed, as the system wiring proved to be correct. Some time later it was discovered that the DIY householder had installed the mid-position valve back-to-front. With existing systems, faults tend to be confined to equipment failure such as defective programmers, valves and pumps. Once again it must be stressed that fault location on such systems is eased considerably when the system is fully understood, and this generally comes with experience.
MOTOR STARTER CIRCUITS The usual cable faults we have already discussed must of course be considered, but faults in the starter itself are usually confined to coil failure or contact deterioration.
Coil failure If this should occur the motor will not start, for the obvious reason that the control circuit is defective.
Reported fault ‘Everything was all right this morning – the motor was running – but this afternoon everything just stopped, and will not start up again.’
Diagnosis Could be operation of circuit protection, coil failure or overload operation due to a motor fault or excessive mechanical loading.
