Conductors for motor loads

[samandmatt]

I have been having a discusion on the proper size wire / overcurrent device for a motor load.


Single Motor
FLC = 26 amp @ 240 Volt, 3 phase.
Source voltage = 240 volt hi-leg delta
Protection via Magnetic Circuit break rated 75'C.

Is #10 THHN rated for this load?

Can this load be protected with a 60 amp circuit breaker?

Does the obilisk to table 310-16 apply?


Thanks,

Michael

 

[iwire]

Re: Conductors for motor loads

Originally posted by michael@nre.cc:
Single Motor
FLC = 26 amp @ 240 Volt, 3 phase.
Source voltage = 240 volt hi-leg delta
Protection via Magnetic Circuit break rated 75'C.

Is #10 THHN rated for this load?

Yes, 310.16 10 AWG THHN = 30 - 40 amps depending on termination temperature ratings

Can this load be protected with a 60 amp circuit breaker?

Yes, could even be larger following Table 430.52 Maximum Rating or Setting of Motor Branch-Circuit Short-Circuit and Ground-Fault Protective Devices

Does the obilisk to table 310-16 apply?

No, look at 240.4(D) then 240.4(G)

Bob

[ July 18, 2003, 03:21 PM: Message edited by: iwire ]

 

[tom baker]

Re: Conductors for motor loads

The obolisk was removed in the 1999 NEC. Its now in Article 240, 240.4(D) Small conductors. What allows you to install a 10 AWG on 60 A OCPD is 240.4(G). The ampere rating of 12 thhn is 30A, and then we apply various rules depending on how it is used.