(1)8-100 Current calculations

When calculating currents that will result from loads, expressed in watts or volt amperes, to be supplied by a

low-voltage alternating-current system, the voltage divisors to be used shall be 120, 208, 240, 277, 347, 416,

480, or 600 as applicable.

(2)8-102 Voltage drop

(1) Voltage drop in an installation shall

(a) be based upon the calculated demand load of the feeder or branch circuit;

(b) not exceed 5% from the supply side of the consumer’s service (or equivalent) to the point of

utilization; and

(c) not exceed 3% in a feeder or branch circuit.

(2) For the purposes of Subrule (1), the demand load on a branch circuit shall be the connected load, if known;

otherwise it shall be 80% of the rating of the overload or overcurrent devices protecting the branch circuit,

whichever is smaller.

(3)8-104 Maximum circuit loading

(1) The ampere rating of a consumer’s service, feeder, or branch circuit shall be the ampere rating of the

overcurrent device protecting the circuit or the ampacity of the conductors, whichever is less.

(2) The calculated load in a circuit shall not exceed the ampere rating of the circuit.

(3) The calculated load in a consumer’s service, feeder, or branch circuit shall be considered a continuous load

unless it can be shown that in normal operation it will not persist for

(a) a total of more than 1 h in any two-hour period if the load does not exceed 225 A; or

(b) a total of more than 3 h in any six-hour period if the load exceeds 225 A.

(4) Where a fused switch or circuit breaker is marked for continuous operation at 100% of the ampere rating

of its overcurrent devices, the continuous load as determined from the calculated load shall not exceed

(a) 100% of the rating of the circuit where the ampacity of the conductors is based on Column 2, 3, or 4

of Table 2 or 4; or

(b) 85% of the rating of the circuit where the ampacity of the conductors is based on Column 2, 3, or 4

of Table 1 or 3.

(5) Where a fused switch or circuit breaker is marked for continuous operation at 80% of the ampere rating of

its overcurrent devices, the continuous load as determined from the calculated load shall not exceed

(a) 80% of the rating of the circuit where the ampacity of the conductors is based on Column 2, 3, or 4

of Table 2 or 4; or

(b) 70% of the rating of the circuit where the ampacity of the conductors is based on Column 2, 3, or 4

of Table 1 or 3.

(6) If other derating factors are applied to reduce the conductor ampacity, the conductor size shall be the

greater of that so determined or that determined by Subrule (4) or (5).

(7) Notwithstanding the requirements of Rule 4-004(1)(d) and (2)(d), the ampacity of the underground

conductors shall not exceed in any case those determined by Subrules (4)(b) and (5)(b) of this Rule.

Ref: Canadian Electrical Code 2012