Cooper Bussmann CT02MAN - Manual (Page 27)

Accessible: (As applied to wiring methods)
Capable of being removed or exposed
without damaging the building structure or
finish, or not permanently closed in by the
structure or finish of the building.
Reprinted with permission from NFPA 70-1999, the National Electrical Code®,
Copyright© 1998, National Fire Protection Association, Quincy, MA 02269. This reprinted
material is not the complete and official position of the National Fire Protection Association,
on the referenced subject which is represented only by the standard in its entirety.
392.6. Installation. (I) Adequate Access.
Cable tray wiring systems should be designed and
installed with adequate room around the cable tray
to allow for the set up of cable pulling equipment.
Also, space around the cable tray provides easy
access for installation of additional cables or the
removal of surplus cables. Where cable trays are
mounted one above the other, a good rule to follow
is to allow 12 to 18 inches between the underside
and the top of adjacent cable trays or between the
structure's ceiling and the top of the cable tray.
392.6. Installation. (J) Conduits and
Cables Supported from Cable Tray.
For the 1996 NEC ® , a significant change was
made in this section. The installations covered in
this section may now only be made in qualifying
industrial facilities.
In Section 392.6(J) of the 1993 NEC ® , cable tray
installations that supplied support for conduits were
not restricted to qualifying industrial facilities. The
1996 NEC
® , Section 392.6(J) text restricts the use
of such installations even though there is no
documented history of problems in non-industrial
installations.
As a result of the change in this section, identical
functional installations in non-qualifying installations
(commercial and industrial) and qualifying industrial
installations have different physical requirements. In
a qualifying industrial installation, a conduit
terminated on a cable tray may be supported from
the cable tray. In a commercial or non-qualifying
industrial installation, the conduit that is terminated
on the cable tray must be securely fastened to a
support that is within 3 feet of the cable tray or
securely fastened to a support that is within 5 feet of
the cable tray where structural members don’t
readily permit a secure fastening within 3 feet. The
conduit of the non-qualifying installation still needs
to be bonded to the cable tray. A fitting may be used
for this bonding even though it will not count as a
mechanical support.
Over 99 percent of the conduits supported on
cable trays are the result of conduits being
terminated on the cable tray side rails
[See Section
392.8(C)] . For over 40 years, it has been common
practice to house the cables exiting the cable tray in
conduits or cable channel where the distance from
the cable tray system to the cable terminations
requires the cable be supported. Several
manufacturers supply UL approved cable tray to
conduit clamps such as the B-Line 9ZN-1158.
In addition to conduit and cables being supported
from cable tray; industrial companies have been
mounting instrumentation devices, push buttons, etc.
on cable tray and cable channel for over 40 years.
This section once lead some to believe that only
conduit or cables may be supported from cable trays
which is not correct as cable tray is a mechanical
support just as strut is a mechanical support.
Because of this, the wording in Section 392.6(J) of
the 2002 NEC
® was changed. Instead of allowing
only cable and conduit to be supported from cable
tray, the code now states that raceways, cables,
boxes and conduit bodies are now permitted to
be supported from the cable tray. Where boxes or
conduit bodies are attached to the bottom or side of
the cable tray, they must be fastened and supported
in accordance with Section 314.23.
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Cable Tray Manual Cooper B-Line, Inc