Opening, Closing, Resetting and Testing a Circuit Breaker with a 9421 Rotary Handle
Opening and Closing with the 9421 Rotary Handle
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Task |
Action |
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|---|---|---|
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Open the circuit breaker |
Turn the operating mechanism from the I (ON) position to the O (OFF) position. |
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Close the circuit breaker |
Turn the operating mechanism from the O (OFF) position to the I (ON) position. |
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Resetting with the 9421 Rotary Handle After a Trip
When the circuit breaker trips, the operating mechanism moves from the I (ON) position to the O (OFF) position.
 CAUTION |
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HAZARD OF CLOSING ON ELECTRICAL FAULT
Do not close the circuit breaker without first inspecting
and, if necessary, repairing the downstream electrical equipment.
Failure to follow these instructions can result in injury or equipment damage.
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The fact that a circuit breaker has tripped does not fix the cause of the fault detected on the downstream electrical equipment.
Follow these steps to reset the circuit breaker after a trip caused by an electrical fault.
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Step |
Action |
Position |
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|---|---|---|---|
|
1 |
Turn the handle from the O (OFF) position to the RESET/LOCK position. The circuit breaker is open. |
O (OFF) |
|
|
2 |
Take precautions to protect yourself (see Taking Precautions Before Responding to a Trip). |
— |
O (OFF) |
|
3 |
Look for the cause of the detected fault (see Identifying the Cause of the Trip). |
— |
O (OFF) |
|
4 |
Clean and test the downstream equipment and the circuit breaker (see Checking Equipment After a Trip). |
— |
O (OFF) |
|
5 |
Turn the handle from the RESET/LOCK position to the I (ON) position. The circuit breaker is closed. |
I (ON) |
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Testing the Trip Mechanism with a 9421 Rotary Handle
| CAUTION |
|---|
|
HAZARD OF NUISANCE TRIPPING
Circuit breaker tests must only be done by qualified electrical
personnel.
Failure to follow these instructions can result in injury or equipment damage.
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When testing the trip mechanism, take precautions against:
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Disrupting operations
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Activating inappropriate alarms
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Triggering unwanted actions
For example, tripping the circuit breaker with the push-to-trip button can lead to inappropriate fault indications or corrective actions (such as switching to an alternate power source).
There is no push-to-trip button on the door of a circuit breaker enclosure with a front operating mechanism.
To check the trip mechanism, the enclosure door must first be opened.
 DANGER |
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HAZARD OF ELECTRIC SHOCK, EXPLOSION, OR ARC FLASH
Overriding the door interlock must only be done by qualified
electrical personnel.
Failure to follow these instructions will result in death or serious injury.
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Follow these steps to test the trip mechanism.
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Step |
Action |
Position |
|
|---|---|---|---|
|
1 |
With the circuit breaker in the O (OFF) position, open the door. |
I (ON) |
|
|
2 |
Turn the circuit breaker from the O (OFF) position to the I (ON) position, using one of the following tools:
The circuit breaker is ready for the test. |
(Trip) |
|
|
3 |
Press the push-to-trip button. The circuit breaker trips. |
O (OFF) |
|
|
4 |
Turn the circuit breaker from the tripped position to the O (OFF) position. The circuit breaker is open. |
O (OFF) |
|
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5 |
Close the door. |
— |
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