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Quick TrayFill and Load Calculations

CAT Cab Type (4 pair) , .19 in. d iameter, 20 lb/kft CAT Cab Type (6 pair), .26 in .d iameter, 40 lb /kftCatalog Height Width Area No. Cables Load No. Cables LoadNumber in. in. in.2 at 50% Fill lbf/lineal ft at 50% Fill lbf/lineal ft

QT2X2 2 1.75 3.5 62 1.24 32 1.28

QT2X4 2 3.75 7.5 133 2.66 70 2.8

QT2X6 2 5.5 11 195 3.9 103 4.12

QT2X8 2 7.5 15 266 5.32 141 5.64QT2X12 2 11.5 23 408 8.16 216 8.64

QT2X16 2 15.5 31 550 11 291 11.64

QT2X18 2 17.5 35 621 12.42 329 13.16

QT2X20 2 19.5 39 692 13.84 367 14.68

QT2X24 2 23.5 47 834 16.68 442 17.68

QT4X4 4 3.75 15 266 5.32 141 5.64

QT4X8 4 7.5 30 532 10.64 282 11.28

QT4X12 4 11.5 46 816 16.32 433 17.32

QT4X16 4 15.5 62 1100 22 583 23.32

QT4X18 4 17.5 70 1242 24.84 659 26.36

QT4X20 4 19.5 78 1384 27.68 734 29.36

QT4X24 4 23.5 94 1668 33.36 885 35.4

T he folllowing tables and formulas are provided to help determine how many cables can be safely carried by each size wire mesh cable tray tray and to determine the appropriate distance between supports for the load,based on number of cables, cable tray size, and bracket type.

Wire Mesh Cable Tray Fill Ratio

Fill ratio = Cross section of cableCross section of tray

According to NEC 392.9 (B), when using ventilated traywith multiconductor control cable, the sum of the cross-sectional areas shall not exceed 50 percent of the interiorcross section of the tray.

The Quick Tray Wire Mesh Cable Tray Fill Table belowshows the number of cables and the load in lbf/lineal footdeveloped by typical 4 pair and 6 pair cable weighing 20lb/kft and 40 lb/kft, respectively.While this table is auseful guide, actual loads must be calculated using thecable specified.

Quick Tray Wire Mesh Cable Tray Fill Table at 50% Fill

Use the following formula to calculate the number of cables that will result in a particular fill ratio, where:

A = Inside tray area, in in. 2

D = Cable diameter, in inches

F = Fill ratio in %

N = Number of cables

The formula is

N = ( F ) * ( A )100 [(D/2) 2 * ]

EXAMPLE:

The installation will use CAT cable at .19 in. diameter, 20 lbper 1000 ft 2.The desired fill ratio is 40%.The wire meshcable tray tray is 2 in. (51mm) high by 2 in. (51mm) wide.

A = 3.5 in.2

D = .19 in.

F = 40%

N = ( 40 ) * ( 3.5 ) = 49 cables100 [(.19/2)

2*

]

Load/foot = 49 cables * 20 lb = 0.98 lb/ft1000 ft.

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Catalog Bracket Width Max. LoadNumber Description in. mm lbs

QTCB4 C Bracket 4 102 259

QTCB8 C Bracket 8 203 216

QTCB12 C Bracket 12 305 108

QTLB4 L Bracket 4 102 259

QTLB8 L Bracket 8 203 216

QTLB12 L Bracket 12 305 108

QTTH Trapeze Hanging Clips 216

Support Maximum Load

Quick TrayFill and Load Calculations

anchor must be evaluated separately. Supports should beplaced within 24 in. (610mm) of a splice on straightsections, and the span between supports should not exceedthe length of tray.Additional supports will be requiredaround bends and when the cable tray level changes.

The load ratings of the hardware that supports the Quick Tray Wire Mesh Cable Tray must also be considered. Loadratings for some commonly used supports are shown in theSupport Maximum Load table below.

Once the load/foot has been determined, the weight oneach support can be determined by multiplying theload/foot by the number of feet between supports.

EXAMPLE:

Weight of span = Load/foot * No. ft between supports

Load/foot figure from the 2 x 2 in. cable tray with 40% fillratio example: .98 lb/ft

Weight of span = .98 * 5 = 4.9 lb

Weight on support = weight of span / 2

Cable Tray Maximum Load in lb/ft According to SpanCatalog Number 5 ft 6 ft 7 ft 8 ft 9 ft 10 ft

QT2X2 17.17 12.54 7.51 6.04 4.77 3.86

QT2X4 18.10 14.00 11.30 9.30 7.40 5.10

QT2X6 25.10 19.80 16.00 13.40 11.00 9.00

QT2X8 25.10 19.80 16.00 13.40 11.00 9.00

QT2X12 36.00 27.70 22.10 18.10 14.60 10.50

QT2X18 65.00 45.50 33.80 26.10 19.40 15.00

QT2X20 65.00 45.50 33.80 26.10 19.40 15.00QT2X24 67.00 48.70 37.80 30.30 23.70 17.00

QT4X8 43.80 35.90 30.10 25.40 21.20 17.00

QT4X12 57.95 43.77 27.77 22.94 18.12 14.68

QT4X20 89.80 71.00 57.70 47.60 38.50 22.00

QT4X24 89.80 71.00 57.70 47.60 38.50 22.00

Supporting Quick Tray Wire MeshCable TrayThe Quick Tray Wire Mesh Cable Tray is sized based onthe number and type of cables required for the currentand future need.A 50% fill ratio should equal the maximum

number of cables pulled in a given cross section. Straightsection supports installed at 5-foot (1.5m) centers aretypical. For support spans greater than 5 feet (1.5m), cableloads must be evaluated to ensure that the span betweenthe supports is suitable for the load.The support and