In North America, there are three main electrical codes:
The National Electrical Code (NEC), used in the United States
Norma Oficial Mexicana (NOM), used in Mexico
The Canadian Electrical Code (CEC), used in Canada
While NOM and NEC are essentially the same document with a translation between Spanish and English, the CEC is a different animal. Before assuming anything between these codes, it is always the right answer to check. But, for a quick guide to major differences, here you go:
Routing in Tray: In Canada, conductors in tray are generally required to have armor when routed in cable tray. There are exceptions to this for certain installations, but this is the reason why armored cable (particularly TECK cable) is so common in Canadian electrical power systems.
Bundled Conductors in Tray: In the United States, we don't have to derate our conductor ampacity for routing in a common tray. This means that a large cable tray filled with 20+ conductors is treated similarly to a single 3-conductor circuit routed in conduit. In Canada, this is not the case. Per the CEC, cable tray is considered the same as any other raceway and the example of 20+ conductors in tray would require a .5 derate for bundling. You could potentially be looking at double the cable.
Terminations: Terminations are one of the most confusing parts about the NEC. The ampacity of a conductor is required to be limited based on the termination temperature rating at the equipment. However, this is about all the NEC says on the matter. The CEC is much clearer. Per the CEC, a 5 foot segment extending out from the equipment must maintain its temperature at or below the equipment termination temperature rating. This means that terminations are not exempt from derating (which they arguably seem to be in the NEC).
Ampacity Tables: The NEC has an entire section devoted to ampacity tables for medium voltage. The CEC, on the other hand, has only one ampacity table for both low voltage and medium voltage conductors aboveground. Underground conductors have some additional tables that may be used. This difference can be both good and bad, as it simplifies ampacity considerations but generally leads to lower medium voltage conductor ampacities than predicted by NEC tables.
Temperature Derating: The NEC permits a temperature derating factor greater than 1 based on ambient temperature. This means that ampacity of conductors can be increased above the values shown in NEC tables where the ambient temperature is cooler than the reference temperature of the table. In the CEC, the temperature derating factor must be 1 or less. Improvements to cable ampacity beyond CEC tables are not permitted.
Bonding Jumpers: The NEC requires that equipment grounding conductors installed for parallel runs in separate raceways must all be fully sized, meaning that each EGC is sized for the full upstream breaker rating from Table 250.122. In the CEC, EGCs are known as bonding conductors, and when installed for parallel runs in separate raceways the size of the bonding conductor is permitted to be divided (in terms of area) across the parallel runs. This means a lot less metal is required for CEC installations.
This is far from an exhaustive list of the differences in design requirements for the CEC and NEC, but these are some of the most impactful. Conductors and overcurrent protection must always be designed in accordance with the codes and standards put forth by the authority having jurisdiction.
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