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Large numbers of electrical engineers have
limited detail knowledge concerning wiring systems.
There is the tendency by engineers to avoid
becoming involved in the details of wiring systems,
leaving the wiring system selection and design to
designers or contractors. Certain decisions must be
made for any wiring system installation, and these
decisions should be made in the design and
construction activities' chain where maximum
impact is achieved at the lowest possible cost.
Deferring design decisions to construction can
result in increased costs and wiring systems
incompatible with the owner's future requirements.
Early in the project's design life, the costs and
features of various applicable wiring systems should
be objectively evaluated in detail. Unfortunately,
such evaluations are often not made because of the
time and money involved. It is important to realize
that these initial evaluations are important and will
save time and money in the long run. The
evaluation should include the safety, dependability,
space and cost requirements of the project. Many
industrial and commercial electrical wiring systems
have excessive initial capital costs, unnecessary
power outages and require excessive maintenance.
Moreover, the wiring system may not have the
features to easily accommodate system changes
and expansions, or provide the maximum degree of
safety for the personnel and the facilities.
Cable tray wiring systems are the preferred wiring
system when they are evaluated against equivalent
conduit wiring systems in terms of safety,
dependability, space and cost. To properly evaluate
a cable tray wiring system vs. a conduit wiring
system, an engineer must be knowledgeable of both
their installation and the system features. The
advantages of cable tray installations are listed
below and explained in the following paragraphs.
• Safety Features
• Dependability
• Space Savings
• Cost Savings
• Design Cost Savings
• Material Cost Savings
• Installation Cost & Time Savings
• Maintenance Savings
CABLE TRAY SAFETY FEATURES
A properly engineered and installed cable tray
wiring system provides some highly desirable safety
features that are not obtainable with a conduit wiring
system.
•Tray cables do not provide a significant path for
the transmission of corrosive, explosive, or toxic
gases while conduits do. There have been explosions
in industrial facilities in which the conduit systems
were a link in the chain of events that set up the
conditions for the explosions. These explosions
would not have occurred with a cable tray wiring
system since the explosive gas would not have been
piped into a critical area. This can occur even
though there are seals in the conduits. There does
have to be some type of an equipment failure or
abnormal condition for the gas to get into the
conduit, however this does occur. Conduit seals
prevent explosions from traveling down the conduit
(pressure piling) but they do not seat tight enough to
prevent moisture or gas migration until an explosion
or a sudden pressure increase seats them. The
October 6, 1979 Electrical Substation Explosion at
the Cove Point, Maryland Columbia Liquefied
Natural Gas Facility is a very good example of where
explosive gas traveled though a two hundred foot
long conduit with a seal in it. The substation was
demolished, the foreman was killed and an operator
was badly burned. This explosion wouldn’t have
occurred if a cable tray wiring system had been
installed instead of a conduit wiring system. A New
Jersey chemical plant had the instrumentation and
electrical equipment in one of its control rooms
destroyed in a similar type incident.
• In addition to explosive gases, corrosive gases
and toxic gases from chemical plant equipment
failures can travel through the conduits to equipment
or control rooms where the plant personnel and the
sensitive equipment will be exposed to the gases.
• In facilities where cable tray may be used as the
equipment grounding conductor in accordance with
NEC
®
Sections 392.3(C) & 392.7, the grounding
equipment system components lend themselves to
visual inspection as well as electrical continuity checks.
WHY CABLE TRAY?
BECAUSE A CABLE TRAY WIRING SYSTEM PROVIDES
SAFE AND DEPENDABLE WAYS TO SAVE NOW AND LATER
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Cable Tray Manual Cooper B-Line, Inc