Electrician Red Seal · Question
A journeyperson is verifying the protective bonding conductor continuity on a 60 A, 3-pole, 600 V motor circuit using a low resistance ohmmeter, sometimes called a ductor tester. They connect one lead of the ohmmeter to the motor frame and the other lead to the main service ground bus. What is an expected acceptable resistance reading for this bonding path?
Protective bonding conductors are intended to provide a very low impedance path for fault currents. A low resistance ohmmeter (ductor) is used to verify this, a
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Question: A journeyperson is verifying the protective bonding conductor continuity on a 60 A, 3-pole, 600 V motor circuit using a low resistance ohmmeter, sometimes called a ductor tester. They connect one lead of the ohmmeter to the motor frame and the other lead to the main service ground bus. What is an expected acceptable resistance reading for this bonding path?
Answer options:
- Greater than 10 Ω
- Between 1 Ω and 5 Ω ✅ Less than 0.1 Ω
- Between 50 Ω and 100 Ω
Correct answer: Less than 0.1 Ω
Explanation: Protective bonding conductors are intended to provide a very low impedance path for fault currents. A low resistance ohmmeter (ductor) is used to verify this, and readings should be extremely low, typically less than 0.1 Ω (100 milliohms), to ensure proper fault clearing. Higher readings indicate a poor connection or undersized conductor.
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