Conduit
Types of conduit

  • Electrical metallic and nonmetallic tubing
  • Nonmetallic flexible conduit and nonmetallic flexible tubing
  • Rigid metal conduit
  • Rigid nonmetallic conduit; and
  • Other types.
  • Conduit shall be permitted under the appropriate electrical codes.
Flexible metal conduit lengths should be less than 6m (20 ft) for each run.

Use of conduit
Conduit should be used when:
  • it is required by code
  • outlet locations are permanent
  • device densities are low
  • flexibility is not required
Design Guidelines
Minimum requirements are found in the appropriate electrical codes.

Pull Boxes and Bends
the maximum conduit length shall be 30m (100 ft) between pull points a pull point shall be provided if there are more than two 90o bends, or equivalent a pull box shall be installed if there is a reverse U-shaped bend the bend radius of a conduit shall be 6 times the internal diameter of the conduit Sizing


Maximum Number of Cables Allowed Based on Fill Rates
Cable Outside Diameter, mm(in)
3.3
4.6
5.6
6.1
7.4
7.9
9.4
13.5
15.8
Trade Size
(.13)
(1.8)
(.22)
(.24)
(.29)
(.31)
(.37)
(.53)
(.62)
16
1/2"
1
 1 0 0 0 0 0 0 0
21
3/4"
6
 5 4 3 2 2 1 0 0
27
1"
8
 8 7 6 3 3 2 1 0
41
1.25"
20
 18 16 15 7 6 4 2 1
53
2"
30
 26 22 20 14 12 7 4 3
78
3"
70
 60 50 40 20 20 17 7 6
103
4"
0
 0 0 0 0 0 30 14 12
Note: This table does not represent all cable and conduit sizes. Check the original standards documentation for additional cable and conduit sizes.


A conduit run shall serve no more than 3 outlet boxes and should increase in size as it approaches the telecommunications room.

Telecommunications Room Termination
Conduits protruding through the floor in a telecommunications room shall be terminated 25-75mm (1-3”) above the floor surface.

Wall-Mounted Public Telephone Locations
Check with your local Carrier for specific requirements or local codes of practice. A minimum 21mm (3/4”) trade size conduit should be provided from the telecommunications closet to serve each wall-mounted public telephone. Where it is necessary to conceal the outlet box directly behind a surface-mounted telephone, the center of the outlet box shall be placed 1220 mm (48 in) above the floor for recessed applications, the conduit and box shall be installed to suit the specific type of mounting.

Hazardous Locations
If it is necessary to place conduit in a hazardous location, the applicable electrical code shall apply. (Australian TS009)

Outdoor Locations
Nonmetallic conduit shall be UV resistant and marked as such. Do not allow moisture to collect in low spots which may freeze and damage the cable or penetrate the cable jacket and wire insulation.

Installation

Conduit Termination
Conduits shall:
  • be reamed to prevent sharp edges
  • be terminated with an insulated bushing (metallic)
  • Conduit System Identification
  • ANSI/TIA/EIA-606 should be consulted for administration of the conduit system
Pull Strings
Pull string or rope shall be placed in installed conduits

Outlet Boxes
maximum conduit trade size vs outlet box size.
Width x Height X Depth (mm)
Maximum Conduit Trade Size
50 x 75 x 64
21
100 x 100 x 57
27
120 x 120 x 64
35


Pull boxes (Draw boxes)
Pull boxes or draw boxes shall be used when
  • Fishing the conduit run.
  • Installing a pull string or cable.
  • Pulling the cable to the box and then looping the cable to be pulled into the next length of conduit.
  • Pull boxes that are used within horizontal distribution shall comply with the pull box requirements of clause 5.2.3 in the original standards documentation.



I would like to thank "cablingdB.com" for relevant information regarding the USA and Canadian Standards. Please visit their site for more information regarding the American Structured Cabling Standards.