Part II — Grounding and Cabling
How you use cable tray might be affected by the upcoming 1999 National Electrical Code
The last Cablegram covered changes in the 1999 NEC in Article 318, Cable Trays. This Cablegram will discuss changes in the grounding and cable articles that affect cable tray installations.
Note: The National Electrical Code® and NEC® are registered trademarks of the National Fire Protection Association, Quincy, MA.
In the 1999 NEC, Article 250, grounding has been reorganized and rewritten. The sections relating to cable trays are now section 250-118, Types of Equipment Grounding Conductors. Cable trays are permitted as item 12, page 96. Item 12 references section 318-3(c) and 318-7. Cable tray bonding is now covered in section 250-96. Bonding jumpers (if any are required) are sized per Table 250-122. The changes appear to be only numbering and rewording and do not change the applicability of cable tray. Call our fax-on-demand, (703) 736-7244, and enter Title II for a discussion of cable tray grounding.
Hazardous Locations Cabling
Type ITC cable listed for use in Class I, Division 1, locations and as indicated in 501-4(a), exception 3. This cable can now be used in cable tray in Class I, Division 1, locations in industrial establishments with restricted public access where conditions of maintenance and supervision ensure that only qualified persons will service the installation.
Listed Type MC cable can be used in Class II (dust hazardous locations), Division 1, with the special characteristics listed in 502-4(b), exception 2. It can be used in cable trays without the one cable diameter spacing between adjacent cables.
Instrument Tray Cable, Type ITC per Article 727, is permitted as open wiring in section 724-2(4). The cable must have a smooth metallic sheath, continuous corrugated metal sheath, or interlocking tape armor applied over the non-metallic sheath per section 727-6. The cable must be supported at intervals less than 6 feet.
Type ITC cable is permitted in industrial establishments where conditions of maintenance and supervision ensure that only qualified persons will service the installation.
Article 340 still permits Tray Cable (Type TC) to be used as open wiring in industrial establishments if the cable construction is such that it matches the crush and impact requirements for Type MC, Article 334, cable. This type of cable is permitted as open wiring, not exceeding 50 feet between the cable tray and utilization equipment or device.
The cable shall be secured and supported at distances not greater than 6 feet.
These changes serve to improve and expand the applications for cable tray.