What happens if (when) a PLC fails?
Someday, some where a PLC will fail due to getting hit by lightning or something. In that case it is easier to replace one PLC than go through replacing all of the individual timers, contacts, relays etc which can be an wiring nightmare. The PLC is solid state and therefore is much less prone to failure than a mechanical timer, relay etc. This can easily be replaced in the feild by any decent electrician.
