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IAEI Magazine | Author: Robert Edwards
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Robert Edwards

Robert Edwards, MASc., IEE (UK), is a retired professional engineer, Province of Ontario. His career includes Northern Electric (now Nortel) cable design engineer; Alcan Wire and Cable (later Alcan Cable), head-cable design and high voltage testing, head-applications engineering, chief engineer, distribution products, and engineering consultant. He is a retired member of Canadian Electrical Code Part I and has chaired the following committees: Section 4 (Conductors), Canadian Electrical Code Part I, CSA Technical Committee, Wiring Products, EEMAC Wire and Cable Technical Committee, Joint NEC-CEC Task Group on Harmonization of Ampacities, and Various CSA Subcommittees, Wire and Cable.


Calculated Demand and Underground Ampacities

The main thrust of this article is to establish that Section 8 of the Canadian Electrical Code Part I does not have adequate rules to address derating factors for continuous loads, or to calculate the minimum ampacity requirements for the safe sizing of conductors and electrical equipment, when the underground ampacity calculation is performed to size conductors, and to propose how solutions to these issues should be developed. The current derating factors for continuous loads apply strictly to installations above ground.