Maximum circuit loading (see Appendix B)
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 2 h period if the load does not exceed 225 A; or
b) a total of more than 3 h in any 6 h period if the load exceeds 225 A.
4) A load of a cyclic or intermittent nature shall be classified as continuous unless it meets th requirements of Subrule 3).
5) 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 the continuous operation marking on the fused switch or circuit breaker and
a) except as required by Item b), shall not exceed 100% of the allowable ampacities of conductors selected in accordance with Section 4; or
b) shall not exceed 85% of the allowable ampacities of single conductors selected in accordance with Section 4.
6) 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 the continuous operation marking on the fused switch or circuit breaker and
a) except as required by Item b), shall not exceed 80% of the allowable ampacities of conductors selected in accordance with Section 4; or
b) shall not exceed 70% of the allowable ampacities of single conductors selected in accordance with Section 4.
7) The continuous load as determined from the calculated load connected to a cablebus shall not exceed the values specified in Subrule 5) or 6).
Source: Rule, 8-104, CSA C22.1:21, Canadian Electrical Code, Part 1 (25th Edition), Safety Standard for Electrical Installations. © 2021 Canadian Standards Association. Please visit store.csagroup.org
