Example Problem: What size metallic auxiliary gutter is required to house 3 - 350 KCMIL THWN copper conductors (feeder) that have 3 - 1/0 AWG, 3 - 1 AWG, and 3 - 2 AWG THWN copper conductors spliced to them?
Step 1: Finding sq. in. area
Table 5, Ch. 9
350 KCMIL THWN = .5242 sq. in.
1/0 AWG THWN = .1855 sq. in.
1 AWG THWN = .1562 sq. in.
2 AWG THWN = .1158 sq. in.
Step 2: Calculating sq. in. area
Table 5, Ch. 9
.5242 sq. in. x 3 = 1.5726 sq. in.
.1855 sq. in. x 3 .5565 sq. in.
.1562 sq. in. x 3 .4686 sq. in.
.1158 sq. in. x 3 .3474 sq. in.
Total = 2.9451 sq. in.
Step 3: Sizing gutter
366.22(A)
sq. in. area divided by 20% = total fill
2.9451 sq. in. ÷ 20% = 14.7255 sq. in.
Step 4: Selecting gutter Chart
4" x 4" = 16 sq. in.
Step 5: Applying 75% fill for splices
366.56(A)
sq. in. of gutter x 75% = fill area
16 sq. in. x 75% = 12 sq. in.
Solution: A 4 in. x 4 in. metallic auxiliary gutter is required with only 12 in. of the gutter space used for splicing conductors.
Solution:
