Motor Bank Tap Conductors

What Are Tap Conductors?

Tap conductors are the short wires that branch off from your main feeder to supply individual motor circuits. Think of the feeder as a highway, and the tap conductors as the on-ramps to each motor.

We need to size them correctly so they:

  1. Don’t overheat
  2. Can handle the current
  3. Match the installation length

Rule Breakdown (CEC 28-110, 14-100)

The sizing method depends on how long your tap conductor is:

1. Tap is 3 meters or less:

Use the same size as the branch circuit conductor it connects to.

Simple Rule:
If the branch conductor is #8 AWG, then the tap conductor is also #8 AWG.

A diagram of a circuit AI-generated content may be incorrect.

2. Tap is between 3 and 7.5 meters:

You must pick the larger of:

  • The ampacity of the overcurrent device it feeds (breaker size), OR
  • One-third the ampacity of the feeder (from Table(s) 1-4)

Example:

  • Individual Motor Over-Current Type (in this case a NTD Fuse) = 40A
  • Feeder = 3/0 AWG copper (200A from Table 2)
  • One-third of feeder = 200 ÷ 3 = 66.7A
  • Termination Temp is 75C

Now compare:

  • 300% (NTD Fuse Multiplier) of FLA for motor with 40A: 40 × 3 = 120A
  • Table 2: #1 AWG = 130A
  • Feeder ÷ 3 = 66.7A → #4 AWG

Pick the bigger → #1 AWG

3.Tap is longer than 7.5 meters:

The tap must be the same size as the feeder.

If the feeder is 3/0 AWG, then the tap is 3/0 AWG too. No exceptions.

Hey, guess what? Rule 4-00 applies to Tap Conductors!