CSLB C-10 Electrical ContractorSafety and TestingHard
A qualified electrical worker is performing maintenance on a motor control center that has been de-energized and locked out. Before beginning work, the worker tests the circuit with a voltage detector. The detector shows no voltage, but the worker notices the detector's battery indicator is low. What is the immediate next action the worker should take according to safety protocols?
- AReport the low battery to a supervisor and wait for instructions.
- BReplace the battery in the voltage detector and re-test.
- CUse a different voltage detector to confirm the reading.
- DProceed with the work, as no voltage was detected.
Show answer & explanationAnswer & explanation
Correct answer: C. Use a different voltage detector to confirm the reading.
According to safety protocols (e.g., NFPA 70E), voltage detectors must be tested both before and after use on a known live source to ensure they are functioning correctly. A low battery indicator casts doubt on the reliability of the 'no voltage' reading, therefore, a known good (and tested) detector must be used to confirm safety before proceeding.
Why the other options are wrong
- A. While reporting is important, the immediate safety action is to re-verify the absence of voltage with reliable equipment, not to wait for instructions that delay safely confirming the state of the circuit.
- B. While replacing the battery is good practice, it doesn't immediately confirm the prior reading. The safest immediate action is to use a detector known to be working.
- D. Proceeding with work with a potentially faulty detector is extremely dangerous and violates safety protocols.
Voltage Detector Verification
The essential safety practice of testing a voltage detector on a known live source immediately before and after testing a circuit for absence of voltage, ensuring the detector is functioning correctly.
- Performed 'prove-before-prove-after' sequence.
- Ensures accurate reading for safety.
- A low battery or malfunction requires re-testing with a reliable device.
Memory trick: Test, Then Test, Then Test Again, Be Sure!