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

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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.

Helpful Tip:

Rule 4-006 applies to Tap Conductors!

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