Cut Sheet

10
Wire Fill Capacity
Use these steps to determine wire fill capacity in Wallduct.
Step 1: Determine the internal raceway area by multiplying the overall width by the overall depth (subtract material thickness).
Example: Assume a raceway 10" wide by 4" deep. Subtract the material thickness from each dimension
(see below). This results in internal raceway dimensions of 9.844" (10" - 0.156") wide by 3.922"
(4" - 0.078"). The internal area for this raceway size would be 38.6 sq. in. (9.844" x 3.922").
Step 2: Determine the number of conductors allowed inside the raceway for a given type and size (types THHN and THWN are
shown in Table 1) of the conductor by multiplying the internal area (calculated in Step 1) by the number of conductors
allowed per square inch (see table 1)..
Example: Calculate how many No. 6 AWG (THHN) conductors you are allowed to place in the 10" x 4"
raceway in Step 1 at 40% wire fill capacity. Multiply the internal area of the raceway by the maximum
number of wires allowed per square inch, from table 1. This results in 304 allowable cables (38.6 sq. in.
x 7.89).
A 20% fill should be used for systems utilizing fittings that have sharp 90° turns. The derating factors of NEC article 310.15(B)(2)(a)
shall apply to conductors installed if the amount of current-carrying conductors exceeds 30 in number, or the sum of the cross-
sectional area of all conductors exceeds 20% of the interior cross-sectional area of the raceway. When tunnels are utilized, the
internal cross-sectional area must be further reduced by 50%. When partitions are utilized, the internal cross-sectional area must
be calculated for each individual compartment.
Deduct for Deduct for
Maximum Raceway Material Material
Width (In.) Thickness Thickness
Left & Right (Bottom)
6" – 18" Steel 0.156" 0.078"
20" – 30" Steel 0.216" 0.108"
6" – 18" Aluminum 0.200" 0.100"
20" – 30" Aluminum 0.250" 0.125"
WIRE SIZE DIAMETER AREA (In
2
) 40% FILL 20% FILL
AWG In. [mm] Sq. In. [Sq. mm] (Per Sq. In.) (Per Sq. In.)
14 0.111 [2.8] 0.0097 [6.3] 41.24 20.62
12 0.130 [3.3] 0.0133 [8.6] 30.08 15.04
10 0.164 [4.2] 0.0211 [13.6] 18.96 9.48
8 0.216 [5.5] 0.0366 [23.6] 10.93 5.46
6 0.254 [6.5] 0.0507 [32.7] 7.89 3.94
4 0.324 [8.2] 0.0824 [53.2] 4.85 2.43
3 0.352 [8.9] 0.0973 [62.8] 4.11 2.06
2 0.384 [9.8] 0.1158 [74.7] 3.45 1.73
Table 1 – Steel Wallduct Wire Fill Capacities for Power
DIAMETER AREA (In
2
) 40% FILL 20% FILL
CABLE/WIRE SIZE In. [mm] Sq. In. [Sq. mm] (Per Sq. In.) (Per Sq. In.)
UNSHIELDED 4-Pair, Cat 5e 0.220 [5.6] 0.0381 [24.6] 10 5
TWISTED PAIR 4-Pair, Cat 6 0.250 [6.4] 0.0491 [31.7] 14 7
TELEPHONE 2-Pair, 24 AWG 0.140 [3.5] 0.0154 [9.9] 20 13
4-Pair, 24 AWG 0.190 [4.8] 0.0263 [18.2] 14 7
25-Pair, 24 AWG 0.410 [10.4] 0.1321 [85.2] 3 1
COAXIAL RG58/U 0.195 [4.9] 0.0298 [19.2] 13 6
RG59/U 0.242 [6.1] 0.0459 [29.6] 9 4
RG6/U 0.270 [6.8] 0.0572 [36.9] 7 3
SHIELDED TYPE 1 0.390 [9.9] 0.1194 [77.0] 3 1
TWISTED PAIR TYPE 2 0.465 [11.8] 0.1698 [109.5] 2 1
TYPE 3 0.245 [6.2] 0.0471 [30.4] 0 4
FIBER OPTIC 2-STRAND 0.180 [4.6] 0.0254 [16.4] 10 8
4-STRAND 0.190 [4.8] 0.0263 [15.3] 14 7
6-STRAND 0.210 [5.3] 0.0346 [22.3] 11 5
FIBER ZIP CORD 0.110 [2.8] 0.0095 [6.1] 42 21
Table 2 – Steel Wallduct Wire Fill Capacities for Data/Communications
NOTE: Wire diameters can vary depending on manufacturer. Verify diameter and adjust fill capacities as required.
Values are per one square inch of Wallduct area.
Editable Guide Form Specs
CAD Drawings