Contactor

All electrical equipment has a definite life span and its replacement depend upon the manufacturer's advice. However I would advise periodic inspection to see the condition of the relay or contactor such as condition of the coil if its visible from outside, including any testings if required; the condition of the contacts, to see they are clean, carbon and rust free, and in good contact or in open position as the case may be; and the connection of the wires to the terminals and the terminal t ...

The main breaker should be sized ad 150% of the motor Full load current, the overload should be sized at 115% or 125% of the Full load current that depends on the service factor. You conductors can be sized at 125% of the motor full load current, and the contactors can be sized at 58% of the motor full load current for the main and delta contactors and 38% for the star contactor.

Normally I would just use contactors of the same value but some engineers use that calculation. Reason ...