Grounded System
In a grounded system, the primary function of the main bonding jumper and of the system bonding jumper is to create the link for ground-fault current between the Equipment Grounding Conductors (EGCs) and the grounded conductor. Table 2.50.5.13(C)(1) is used to establish the minimum size of main and system bonding jumpers. Unlike the grounding electrode conductor, which carries current to the ground (via connection to a grounding electrode), the main and system bonding jumpers are placed directly in the supply-side ground-fault current return path.
Where the largest ungrounded supply conductor exceeds the parameters of Table 2.50.5.13(C)(1), Note 1 requires a proportional relationship between the ungrounded conductor and the main or system bonding jumper. Where the service-entrance conductors are larger than 500 mm² copper or 850 mm² aluminum, the bonding jumper must have a cross-sectional area of not less than 12 1⁄2 percent of the cross-sectional area of the largest phase conductor or largest phase conductor set. In equipment such as panelboards or switchboards that are listed for use as service equipment, the manufacturer provides a bonding jumper that can be installed as the main or system bonding jumper. It is not necessary to provide an additional bonding jumper.
Philippine Electrical Code Requirement
| Size of Largest Ungrounded Conductor or Equivalent Area for Parallel Conductors mm² |
Size of Grounding Conductor or Bonding Jumper* mm² |
||
|---|---|---|---|
| Copper | Aluminum or Copper-Clad Aluminum | Copper | Aluminum or Copper-Clad Aluminum |
| 30 or smaller | 50 or smaller | 8.0(3.2) | 14 |
| 38 or 50 | 60 or 80 | 14 | 22 |
| 60 or 80 | 100 or 125 | 22 | 30 |
| Over 80 through 175 | Over 125 through 250 | 30 | 50 |
| Over 175 through 325 | Over 250 through 400 | 50 | 80 |
| Over 325 through 500 | Over 400 through 850 | 60 | 100 |
| Over 500 | Over 850 | See Notes 1 and 2 | |
Notes:
1. If the ungrounded supply conductors are larger than 500 mm² copper or 850 mm² aluminum, the grounded conductor or bonding jumper shall have an area not less than 12 1∕2 percent of the area of the largest ungrounded supply conductor or equivalent area for parallel supply conductors. The grounded conductor or bonding jumper shall not be required to be larger than the largest ungrounded conductor or set of ungrounded conductors.
2. If the ungrounded supply conductors are larger than 500 mm² copper or 850 mm² aluminum and if the ungrounded supply conductors and the bonding jumper are of different materials (copper, aluminum, or copper-clad aluminum), the minimum size of the grounded conductor or bonding jumper shall be based on the assumed use of ungrounded supply conductors of the same material as the grounded conductor or bonding jumper and will have an ampacity equivalent to that of the installed ungrounded supply conductors.
3. If multiple sets of service-entrance conductors are used as permitted in 2.30.4.1, Exception No. 2, or if multiple sets of ungrounded supply conductors are installed for a separately derived system, the equivalent size of the largest ungrounded supply conductor(s) shall be determined by the largest sum of the areas of the corresponding conductors of each set.
4. If there are no service-entrance conductors, the supply conductor size shall be determined by the equivalent size of the largest serviceentrance conductor required for the load to be served.
*For the purposes of applying this table and its notes, the term bonding jumper refers to main bonding jumpers, system bonding jumpers, and supply-side bonding jumpers.