Electrician Red Seal · Question
A Red Seal electrician is requested to add several new circuits to an existing 100 A, 120/240 V, single-phase residential service. The current calculated load for the dwelling is 85 A. The new circuits are expected to add an additional 20 A to the total demand. According to the Canadian Electrical Code (CEC), what action should the electrician recommend regarding the existing service?
When adding circuits, the total calculated load must not exceed the rating of the service. The existing load is 85 A, and new circuits add 20 A, bringing the to
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Question: A Red Seal electrician is requested to add several new circuits to an existing 100 A, 120/240 V, single-phase residential service. The current calculated load for the dwelling is 85 A. The new circuits are expected to add an additional 20 A to the total demand. According to the Canadian Electrical Code (CEC), what action should the electrician recommend regarding the existing service?
Answer options: ✅ Recommend upgrading the service to 200 A.
- Proceed with adding the new circuits as the service has a 15 A margin.
- Apply a demand factor of 70% to the new circuits to fit within the existing service.
- Install a load management system to avoid exceeding the service rating.
Correct answer: Recommend upgrading the service to 200 A.
Explanation: When adding circuits, the total calculated load must not exceed the rating of the service. The existing load is 85 A, and new circuits add 20 A, bringing the total to 105 A. Since the existing service is 100 A, it will be overloaded. Rule 8-106 requires that the service capacity be adequate for the calculated load, thus an upgrade to 200 A is necessary.
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