Electrician Red Seal · Question
An industrial facility requires grounding for a new 480 V, three-phase, 60 Hz electrical service. The facility's soil resistivity is high, making a single driven electrode impractical for achieving the required resistance. According to the CEC, what is the maximum permissible resistance to ground for a grounding electrode system?
CEC Rule 10-106(1) states that the grounding electrode system resistance to ground must not exceed 25 Ω. If a single electrode does not achieve this, additional
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Question: An industrial facility requires grounding for a new 480 V, three-phase, 60 Hz electrical service. The facility's soil resistivity is high, making a single driven electrode impractical for achieving the required resistance. According to the CEC, what is the maximum permissible resistance to ground for a grounding electrode system?
Answer options:
- 5 Ω
- 10 Ω ✅ 25 Ω
- 50 Ω
Correct answer: 25 Ω
Explanation: CEC Rule 10-106(1) states that the grounding electrode system resistance to ground must not exceed 25 Ω. If a single electrode does not achieve this, additional electrodes or a different system must be used. While common practice may aim for lower resistance (e.g., 5 Ω), the code specifies 25 Ω as the maximum.
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