Types of Bonding Conductors
There are several bonding conductors in the CEC:
- Bonding Conductor: Connects non-current-carrying metal parts to the grounding system.
- Bonding Jumper: Connects sections of metal enclosures.
- System Bonding Jumper: Connects the grounded conductor (neutral) to the equipment grounding/bonding system.
Bonding Conductors vs. Bonding Jumpers
(Both are part of the bonding system — but they serve different roles.)
1. Bonding Conductor
What it is:
The main wire that connects non-current-carrying metal parts (like enclosures, raceways, pipes, etc.) to the grounding system.
Think of it as:
The main safety highway that connects metal parts to earth ground or to the main grounding point.
Example:
A #6 copper wire running from your metal panelboard enclosure to the ground bus — that’s a bonding conductor.
2. Bonding Jumper
What it is:
A shorter bonding wire that connects two metal parts together so they are electrically continuous.
Think of it as:
A bridge between two pieces of metal that might otherwise be electrically isolated.
Types:
- Main Bonding Jumper: Connects the neutral (grounded conductor) to the bonding system (usually in the main service panel)
- Equipment Bonding Jumper: Connects enclosures, conduits, or devices together (like across conduit fittings or motor frames)
- System Bonding Jumper: Connects the neutral to bonding system in separately derived systems (like transformers)
CEC Rules: 10-604 (system jumper), 10-614 (equipment jumper)
Example:
A short wire bonding the two ends of a flexible conduit where continuity might otherwise be lost — that’s a bonding jumper.
Tip: Sizing Bonding JUMPERS and CONDUCTORS is the same!!!
How to Size Bonding Conductors (CEC) For SERVICE EQUIPMENT
Rule 10-616(2):
Step 1: Identify the Largest Ungrounded Conductor
Bonding conductor size is based on the ampacity of the size of the largest ungrounded (live) conductor in the system — this could be a single conductor or the largest in a parallel set.
Example: If the largest conductor feeding your panel is a #3 AWG copper, go to Table(s) 1-4, and find the ampacity--that’s your reference point.
Step 2: Use CEC Table 16
Once you know the size of the largest ungrounded conductor ampacity, go to CEC Table 16 to find the minimum size of the bonding conductor.
How to Size Bonding Conductors (CEC) For OTHER THAN Service Equipment
Rule 10-616(3):
Step 1: Identify the Over-Current Device Protecting the Conductor/Equipment
The Bonding Conductor cannot be less than the O/C protecting the conductors or Equipment.
OR
IF the largest ungrounded conductor has been UPSIZED due to voltage drop, then you HAVE TO go with that instead of the O/C device.
Step 2: Use CEC Table 16
Once you know the size of the Over-Current Device go to CEC Table 16 to find the minimum size of the bonding conductor.
FUN FACT: If you are trying to figure out Bonding for a Relocatable Structure, you use Table 41
EXAMPLES:
What is the Bonding Conductor size required for a 30 HP, 600-volt, 3-phase squirrel cage motor with a service factor of 1.15 that is operating under normal circumstances and protected by a NTD fuse?
This is NOT SERVICE.
So it depends on if the Conductors feeding the branch circuit were up-sized due to Voltage Drop.
The question does not specify that it was, so we need to figure out the O/C size.
Step 1: What is the question asking for?
-Over-current. So we pick out only the information that helps us.
Step 2: What do we have?
-Motor Info and Non-Time Delay Fuse
Step 3: What do we need?
-FLA (Table 44) Over-current multiplier (Table 29) Over-Current Size (Table 13)
32A * 300%= 96A
90A NTD Fuse.
Table 16:
90A is not an option, so we go UP.
100A-
Copper: #8awg
Aluminum: #6awg
What size of aluminum bonding conductor is needed for a 30 HP, 600VAC, 3-phase SCIM protected by a NTD fuse and supplied by a #6awg R90(XLPE)?
This questions doesn’t mention any type of Over-Current device, so the supply size is the clue.
Step 1: What is the question asking for?
-Bonding conductor size BUT……..
-Conductor Size.
Ask yourself: WHICH CONDUCTOR? WHAT’S THE DUTY?
Step 2: What do we have?
-Motor Info and Duty Type
Step 3: What do we need?
-FLA (Table 44) Duty: Continuous
32A * 125%= 40A
Table 2 (75°C): #8awg
Since we calculated a #8awg, but the question says a #6awg…that means it was up-sized due to voltage drop.
Table 2 tells us that a #6awg (75C) is 65A
Table 16 says “NOT EXCEEDING”, so we have to go to 100A.
Aluminum is #6awg.