OVERCURRENT PROTECTION DEVICE FOR TAPS (10 FT TAP)
240.21(B)(1)
Example Problem: What size overcurrent protection device is required for a 10 ft (3 m) tap from a junction box that is supplied by a feeder with a 500 amp overcurrent protection device?
Step 1: Calculating minimum size tap
240.21(B)(1)(4)
A = 500 A OCPD ÷ 10 (1/10)
A = 50
Step 2: Sizing conductors
Table 310.16
8 AWG THWN cu. = 50 A (Terminated at 75 degree C)
Step 3: Verifying size based on conductor ampacity
240.21(B)(1)(4)
50 A is equal to 50 A
[50 A x 10 (1/10) = 500 A OCPD]
Step 4: Calculating OCPD
240.4(E), 240.21(B)(1)(1), and 240.4(B)
50 A conductors permit 50 A OCPD
Solution: The size overcurrent protection device is 50 amps.
