Smallest cable size run for motor.

[Pitt123]

What is the smallest cable size that can be run for a motor? Can a #14, or #16 be run as long as its large enough for motor current and overload protects it? What is good practice for smallest size?

 

[480sparky]

Can't use 16.... 310.15.

As for anything else, the motor load will determine the size.

 

[kwired]

general rule

310.5 Minimum Size of Conductors.
The minimum size of conductors shall be as shown in Table 310.5, except as permitted elsewhere in this Code.

Table 310.5 Minimum Size of Conductors

Minimum Conductor Size (AWG)
Conductor Voltage Rating (Volts) Copper Aluminum or Copper-Clad Aluminum
0–2000 14 12
2001–8000 8 8
8001–15,000 2 2
15,001–28,000 1 1
28,001–35,000 1/0 1/0

I do not see anything in 430 that allows smaller than 14 for motor conductors, control conductors may be allowed to be smaller if certain conditions are met.

I see that copying a table from NEC on CD does not retain the table format.

left column is voltage next column is copper conductor size and the right column is aluminum conductor size

 

[Pitt123]

general rule

310.5 Minimum Size of Conductors.
The minimum size of conductors shall be as shown in Table 310.5, except as permitted elsewhere in this Code.

Table 310.5 Minimum Size of Conductors

Minimum Conductor Size (AWG)
Conductor Voltage Rating (Volts) Copper Aluminum or Copper-Clad Aluminum
0?2000 14 12
2001?8000 8 8
8001?15,000 2 2
15,001?28,000 1 1
28,001?35,000 1/0 1/0

I do not see anything in 430 that allows smaller than 14 for motor conductors, control conductors may be allowed to be smaller if certain conditions are met.

I see that copying a table from NEC on CD does not retain the table format.

left column is voltage next column is copper conductor size and the right column is aluminum conductor size

Would this apply to VFD cables as well? Or do these typically have a higher rating?

 

[Smart $]

What is the smallest cable size that can be run for a motor?

18AWG under special condition (junction box separate from motor)

See 430.22(F)

Expanded conditions for using #16 and #18 have been proposed and accepted in principle for the 2011 NEC.

 

[Pitt123]

18AWG under special condition (junction box separate from motor)

See 430.22(F)

Expanded conditions for using #16 and #18 have been proposed and accepted in principle for the 2011 NEC.

If #16 or #18 is currenly not allowed to be run for the motor branch circuit then why would cable companies sell VFD cable that is this small? Is this because the NEC does not apply everywhere?

 

[skeshesh]

18AWG under special condition (junction box separate from motor)

See 430.22(F)

Expanded conditions for using #16 and #18 have been proposed and accepted in principle for the 2011 NEC.

Good one Smart I forgot about that one.

Cool avatar GIF by the way.

 

[Smart $]

If #16 or #18 is currenly not allowed to be run for the motor branch circuit then why would cable companies sell VFD cable that is this small? Is this because the NEC does not apply everywhere?

That would be my guess.

 

[iwire]

If #16 or #18 is currenly not allowed to be run for the motor branch circuit then why would cable companies sell VFD cable that is this small? Is this because the NEC does not apply everywhere?

Or to everything, a machine manufacturer could run 16 or 18 to motors in a piece of machinery.

 

[weressl]

What is the smallest cable size that can be run for a motor? Can a #14, or #16 be run as long as its large enough for motor current and overload protects it? What is good practice for smallest size?

In industry, the smallest size is usually limited to #12AWG.