The Canadian Electrical Code provides
safety standards for installation and maintenance of
electrical equipment. Its object is to prevent electrical fire
and shock hazards when we follow its rules. The CEC is not
intended as a design standard, but only a set of least
requirements to help us achieve safe electrical installations.
For the most part, the CEC provides us with
direction and guidance on how to achieve safe electrical
wiring and equipment installations. But in Section 2 we also
find a number of rules on working safely when operating and
maintaining electrical equipment, and how to arrange
electrical facilities so as to reduce electrical hazards.
Rules 2-300 to 2-322 offer us some mere minimum requirements
that we must at all times enhance with other requirements and
safety regulations for working in an electrical environment.
It goes without saying that our labour, building and fire
regulations must be strictly followed, since they add much
greater detail to these rules.
Our list of personal safety rules begins
with Rule 2-300, a motherhood statement, advising us that
electrical equipment must be kept "in safe and proper
condition." It tells us that emergency equipment such as
fire alarm systems and emergency power must be tested to
ensure they will be available when we need them. It reminds us
that seldom-used equipment should be checked before use and
that defective wiring or equipment must be repaired or
disconnected before it causes any problems. None of this is
news, only a heads up and common sense.
Rule 2-302 addresses a special issue,
maintaining electrical equipment in hazardous locations where
flammable materials or gases may be present. You will recall
that Section 18 of the code defines hazardous locations as
places where flammable or explosive gases, dusts or fibres are
present in sufficient quantity to create a fire or explosion
hazard. Electrical equipment and wiring in these areas must
meet Section 18 requirements in all cases. And Rule 2-302 adds
what must be perfectly obvious—that alterations and repairs
must not be done on live equipment, also that it’s important
to maintain hazardous location equipment in its original, safe
condition. Although the rule is not that specific, it follows
that except for approved, intrinsically safe instruments,
electrical tools and equipment must also meet the standards
for use in each hazardous location.
Rule 2-304 prohibits working on live
electrical equipment unless absolutely necessary. There may be
times when shutting down may be impracticable or when
inspection and testing of live equipment becomes necessary.
But in all other cases, Rule 2-304 requires a lockout
procedure, warning signs and sentries to ensure that equipment
is not accidentally re-energized while people are working on
it. Rule 2-304 provides a minimum of detail. Obviously, its
requirements must be beefed up with other legislation and
guidelines on disconnection procedures and working with live
equipment.
Rule 2-306 recognizes that occasionally we
do have to work with the power on, and when this becomes
necessary, it tells us to use rubber gloves,
electrically-resistant footwear and rubber mats to isolate
workers from electrical shock risks and make the task as safe
as possible. Although not specified in the CEC, we should add
to this list, fire-resistant clothing, face and eye
protection, head protection and other precautions to help us
control the harmful effects of electrical flash or explosion.
To further enhance our personal safety,
Rules 2-308 and 2-310 provide some minimum requirements for
working space, entry and exit space to electrical rooms,
vaults and other locations where electrical equipment is
installed.
Rule 2-308 requires a minimum of one metre
working space about electrical equipment at all locations
where access is required for operation or maintenance. This
obviously applies to the front, but may also apply to the
sides or backs of equipment where access is necessary. Please
note that the prescribed minimum distance is in addition to
any space necessary for devices such as draw-out
circuit-breakers or motor starters when in their fully drawn
out positions. The rule also directs us to Table 56, which
provides minimum working space around bare live parts.
Rule 2-310 further helps us reduce the
risks by stipulating that when equipment is rated 1200 amperes
or higher or above 750 volts, the exit route must be at least
1.5 metres wide when exiting a room during an electrical
equipment fault. An acceptable alternative would be to provide
a second exit that avoids having to pass electrical equipment
under fault conditions. Also, electrical room doors must be
capable of opening from inside the room without using a key or
tools.
Finally, Rules 2-312 to 2-320 ask us to
ensure that working space and exits are not blocked by
storage, that flammable materials not be stored near
electrical equipment and that adequate lighting and drainage
be provided. The purposes of all these common sense rules are
to ensure a safe electrical environment to the extent possible
and the use of safe procedures when working on or operating
electrical equipment.
As with previous articles, you should
always consult the electrical inspection authority in each
province or territory as applicable for a more precise
interpretation of any of the above.
Leslie Stoch, P.E. is principal of L. Stoch & Associates,
providing electrical engineering and ISO 9000 quality systems
consulting. Prior to that, he spent over 20 years with Ontario Hydro as
an electrical inspection manager and engineer. Les holds a B.S. in
electrical engineering from Concordia University in Montreal.
|
