The Canadian Electrical Code, Section 6
provides us with some important rules for installing service
equipment, wiring methods and metering. The following rules
apply to electrical utilities and their customers at the
service entrance, the point where an electrical utility
connects to a customer’s electrical installation. This
article covers some of the main requirements on the number and
locations of electrical services and defines the terms used in
the code.
To avoid undue hazards to people working on
electrical systems and to ensure that electrical services can
be readily disconnected in an emergency, Rule 6-102 requires
that the number of "supply services" be limited.
There must not be more than one to a building except for
special
situations including:
• Fire pumps
• Industrial or complex buildings; or
• Buildings divided into a number of
units where all units are at grade level with separate
entrances
To jog your memory, the term "supply
service" refers to an electrical utility’s wiring from
its power distribution system to the point of connection at a
customer’s premises.
For the same reasons, Rule 6-102 also says
that when a customer needs to have more than one "service
box," the "service boxes" should be grouped in
one location. If that’s not possible for valid reasons, a
diagram must be posted at each "service box" showing
the locations of all other main disconnection points. This is
so that people can be assured that all sources of supply are
disconnected when that becomes necessary.
The term "service box" refers to
the main service equipment containing the main circuit-breaker
or switch and fuses for an electrical utility customer’s
electrical system, and approved for use as service entrance
equipment.
For some very practical reasons, emergency
and life safety systems belong in an independent category with
some different rules. Going back to the CEC exception for fire
pumps, Rule 32-204 that tells us they can have a separate
"service box," and that despite Rule 6-102, this
equipment may be located apart from the building’s main
service. However, each fire pump service must be well marked
and identified. For a more secure supply in an emergency, fire
pumps alternatively fed from a building’s standby power, are
required by Rule 32-206 to have a nearby transfer switch for
each fire pump, or within each fire pump controller.
Rule 6-104 limits the number of services
from one supply by specifying that: The number of
"consumer’s services" of the same voltage and
characteristic, terminating at one "supply service,"
run to, on, or in any building, shall not exceed four, unless
a deviation is allowed in accordance with Rule 2-030. A
typical example installation would be electrical utility
conductors to a multiple metering arrangement supplying
several different units within a building. The electrical code
reference to Rule 2-030 means you need the permission of an
inspector if you wish to exceed that number.
To avoid having to look it up, a
"consumer’s service" is all of the wiring and
equipment within the customer’s premises past the point
where the electrical utility makes its connections. An
electrical utility’s connections are usually made either at
the customer’s overhead service mast, the top side of the
metering equipment or at the main "service box"
depending on the size and type of supply.
To facilitate disconnecting the electrical
supply, Rule 6-200 says each "consumer’s service"
should have its own "service box" except when the
main service is subdivided in an outdoor multiple or dual lug
meter base, up to 600 amperes and 150-volts to ground. For the
purposes of Rule 6-104, each metering point can be considered
a "consumer’s service." You can have several
"service boxes" in a building supplied from the same
metering arrangement.
Rule 6-106 tells us that an electrical
installation or part of an installation must not at any time
be supplied by more than one source. If an installation has
several "supply services" or other sources of supply
such as standby power, there must be transfer switching or key
interlocking among the supplies to prevent connection to more
than one supply system at a time.
Rule 6-206 tells us where we may locate the
main electrical service equipment and limits it to the
following:
• The location must meet the electrical
utility’s requirement.
• The service equipment must be
"readily accessible."
• The service equipment must be as
close as possible to the point where the service conductors
enter the building.
• Not in any location where it would be
dangerous to enter or without sufficient working space, such
as where the ambient temperature exceeds 30C or where there
is less than 2m headroom
• Inside the building unless there are
valid reasons to locate the service equipment outdoors, such
as when buildings have high humidity, a corrosive or
hazardous, explosive atmosphere, when permitted by an
electrical inspector
• When outdoors, equipment must be
weatherproof or protected from the weather and protected
from damage when less that 2 m above the ground.
"Readily accessible" means
capable of being reached quickly without having to climb over
anything or using a ladder.
As you can appreciate, the Canadian
Electrical Code, Section 6 contains important rules governing
interconnections between an electrical utility system and its
customers. As with previous articles, you should check with
the electrical inspection authority in each province or
territory as applicable for a more precise interpretation 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
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