D-4 Group Motor Installations
From NEC Table 310.16 we need to use 8 AWG for the motor branch
circuit. Per NEC 430.28 the individual motor tap conductors can be
sized down to 1/3 the ampacity of the trunk but not less than 125% of
the specific motor’s FLC on the tap. This reduction is further
conditionally based on the tap being not more than 25 feet. NFPA 79,
7.2.10.4 and Table 7.2.10.4 restrict the size reduction by the size of
the branch circuit fuse size and tap conductor size. For the above case
we have used a 40 A time-delay fuse. NFPA 79, Table 7.2.10.4
indicates that the smallest tap conductor can be 12 AWG. NEC Table
310.16 for wire ampacity allows 12 AWG (25 A) to be used in all taps
for this application. See the final Group motor circuit design in the
following figure:
8 AWG motor branch trunk
12 AWG motor trunk tap conductors are
permissible with 40A Time Delay fuse; 14 AWG
are permissible with 50A Inverse Time circuit
breaker. (NFPA 79 Table 7.2.10.4)
40A Time Delay
or 50A Inverse Time CB
Note, the ArmorStart and motor cable are UL Listed
together and supplied by Rockwell Automation.
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10 HP DOL-AS 10 HP DOL-AS 2 HP VFD-AS 2 HP VFD-AS 2 HP VFD-AS 2 HP VFD-AS
SF=1.15
14A FLC
10 HP
SF=1.15
7.6A FLC
5 HP
SF=1.15
3.4A FLC
2 HP
SF=1.15
2.1A FLC
1 HP
SF=1.15
2.1A FLC
1 HP
SF=1.15
2.1A FLC
1 HP
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