wireways selection guide    wireways selection guide    wireways selection guide

 

Wireways are designed to protect cables from environmental contaminants such as dust, dirt, oil, and moisture.

 

Basic Information

 

Wireways—sometimes known as "troughs" or "gutters" within the electrical contracting field—are commonly used to control wiring in environments where contaminants may cause problems. Depending on the product type, they can be mounted to walls or ceilings, secured under flooring, or laid out in a hybrid design in unique cable management systems.

 

The layout of a cable management system, consisting of various connected wireway shapes, is shown below.

 

wireways selection guide

 

A wireway is typically produced as a metallic or non-metallic trough with hinged or removable covers, so that the cables contained are well-protected but still accessible. The high cost of manufacturing and installing wireways limits their use to small sections of cable management systems, while most systems primarily consist of cable trays, conduit, and other types of raceway.

 

wireways selection guide

Cables being fed into a pull-through wireway.

 

When connected, wireways must be reinforced using special fittings and gaskets between sections.

 

Types

Wireways are produced in three different forms, as shown in the table below.

 

Type

Description

Image

Lay-in

One side of trough opens via hinges; wires may be laid in instead of pulled through.

 wireways selection guide

Pull-through

Wires or cables must be strung through trough; may still have a hinged lid to allow cable access.

 wireways selection guide

Cable trough

Simple trough with no cover.

 wireways selection guide

 

Standards and Applications

 

Because they are frequently used in hazardous environments, the use of wireways is governed by several important standards and approval ratings. These ratings help determine a wireway's appropriateness for a specific application or environment.

 

UL 870

The Underwriters Laboratories UL 870 standard includes guidelines for safe use of wireways, including recommended maximum conductor sizes and number of conductors for particular wireway sizes. The table below is based on UL 870 Table 7.1 and describes the maximum allowable cable size for some common wireway sizes.

 

Note that the UL 870 table specifies cable diameter in both American wire gauge (AWG) and circular mil (kcmil). Smaller AWG values indicate larger cables and vice versa, while circular mil is typically used for cables larger than AWG 4/0.

 

Wireway Size (inches)

Maximum Cable Size

2.5 x 2.5

AWG 2

3 x 3

AWG 1

4 x 4

AWG 4/0

4 x 6

AWG 4/0

6 x 6

500 kcmil

12 x 6

500 kcmil

8 x 8

900 kcmil

10 x 10

1250 kcmil

12 x 12

2000 kcmil

 

NEMA

Many covered wireways, as well as most enclosures, are often provided with a NEMA type, which is standardized by the National Electrical Manufacturers Association NEMA ICS 6 standard. NEMA types are numerical values (sometimes qualified by a letter) which describe an enclosure's ability to protect contents against various types of environmental hazard. The table below shows common NEMA types along with the hazards they are designed to withstand. (The 'N' in the 'Chemicals' column indicates that NEMA 5 and 12 enclosures are only effective against noncorrosive chemicals.)

 

Rating

Indoor

Outdoor

Rain/Water

Dust

Ice

Dirt

Submersion

Chemicals

1

x

 

 

 

 

x

 

 

2

x

 

x

 

 

x

 

 

3

 

x

x

x

x

 

 

 

4X

x

x

x

x

x

 

 

x

5

x

 

 

x

 

x

 

N

6

x

x

x

 

x

 

x

 

12

x

 

x

 

 

x

 

N

13

x

 

x

x

 

 

 

x

 

Additional Standards

Additional standards pertaining to wireways are listed below.

 

  • IEEE NEC - National Electrical Code (2012)
  • NFPA 70 - National Electrical Code (2013)
  • CSA C22.2 No. 26 - Construction and test of wireways, auxiliary gutters, and associated fittings

 

References

 

Cooper Industries - Wireway Selection (pdf)

 

NEMA Website

 

Steven Engineering / Square D - Wireways (pdf; includes sections from 1993 NEC for reference)

 

Image credits: Hoffman | Legrand | Hoffman | Enduro | Hoffman | HP