Service equipment is your service panel and associated items. Example your building main.
AC System is intended to mean an electrical installation in which the energy provided by that installation to utilization equipment is derived from a single energy source. For example, an electrical installation supplied from a transformer bank or a transformer is considered an AC System. An installation supplied by a different transformer would be considered a different system.
****NOTE- This all applies only to the 2002 CEC as there have been changes to this in the 2006 CEC. The changes are at the bootom.
Table 16- is used to find the size of the bond conductor.
Ex. You have a water heater that is fed from a double 30 amp breaker. According to the table the minimum size required for the Bond conductor is 12 awg.
Table 17 is used to find the minimum size of Grounding conductor for AC Systems.
Ex. Your house has a 100 amp service. The main breaker is 100 amp and your service conductors are #3 awg RW90. The table goes by the ampacity of the largest service conductor. So according to table 2 #3awg RW90 has an ampacity of 105 amps. So using Table 17 the minimum size Grounding conductor has to be #6awg.
Table 18 was used for grounding a service raceway and equipment that was fed from an ungrounded delta system. Use the table to find out what size grounding conductor is used to ground the service equipment enclosure to ground.
The changes to these Tables in the 2006 CEC are:
Table 16 has been changed to relate to the largest ungrounded conductor and not the size of the overcurrent device.
Table 17 is now called Minimum Size Of Grounding Conductor.
Table 18 has been deleted.
I hope this helps.