De-Energizing the Circuit Breaker

Isolation Capacity

ComPact NSX circuit breakers offer positive contact indication and are suitable for isolation in accordance with standards IEC/EN 60947-1 and 2. The O (OFF) position of the actuator is sufficient to isolate the circuit breaker concerned.

The following marking on the faceplate label indicates that the circuit breaker is capable of isolation:

To confirm this capability, standards IEC/EN 60947-1 and 2 require specific shock withstand tests.

ComPact NSX circuit breakers can be locked in the O (OFF) position to allow work to be carried out with the power off in accordance with installation rules. The circuit breaker can only be locked in the open position if the circuit breaker is in the O (OFF) position.

NOTE: Locking a ComPact NSX circuit breaker in the open position is sufficient to isolate the circuit breaker.

The locks depend on the type of actuator:

For circuit breakers with toggle handles, refer to the locking accessories.
For circuit breakers with rotary handles, refer to how to lock the circuit breaker with direct rotary handle and how to lock the circuit breaker with extended rotary handle.
For circuit breakers with motor mechanisms, refer to how to lock the circuit breaker.

Maintenance and Servicing Work on Installation

DANGER
HAZARD OF ELECTRIC SHOCK, EXPLOSION, OR ARC FLASH Apply appropriate personal protective equipment (PPE) and follow safe electrical work practices. See NFPA 70E or CSA Z462 or local equivalent. This equipment must only be installed and serviced by qualified electrical personnel. Turn off all power supplying this equipment before working on or inside equipment. Always use a properly rated voltage sensing device to confirm that power is off. Put back all devices, doors, and covers before turning on power to this equipment. Repair the installation immediately if an insulation fault occurs during operation. Failure to follow these instructions will result in death or serious injury.

DANGER

HAZARD OF ELECTRIC SHOCK, EXPLOSION, OR ARC FLASH

Apply appropriate personal protective equipment (PPE) and follow safe electrical work practices. See NFPA 70E or CSA Z462 or local equivalent.
This equipment must only be installed and serviced by qualified electrical personnel.
Turn off all power supplying this equipment before working on or inside equipment.
Always use a properly rated voltage sensing device to confirm that power is off.
Put back all devices, doors, and covers before turning on power to this equipment.
Repair the installation immediately if an insulation fault occurs during operation.

Failure to follow these instructions will result in death or serious injury.

Turn off all power supplying the equipment before working on or inside equipment. For a partial powering down of the installation, the installation and safety rules require clearly labeling and isolating the feed being worked on.

Maintenance Work Following Fault Trip

WARNING
HAZARD OF CLOSING ON ELECTRICAL FAULT Do not close the circuit breaker again without first inspecting and, if necessary, repairing the downstream electrical equipment. Failure to follow these instructions can result in death, serious injury, or equipment damage.

The fact that a protection has tripped does not remedy the cause of the fault detected on the downstream electrical equipment.

The following table describes the procedure to be followed after a fault trip:

Step	Action
1	Isolate the feed before inspecting the downstream electrical equipment.
2	Look for the cause of the detected fault.
3	Inspect and, if necessary, repair the downstream equipment.
4	Inspect the equipment in the event of a short-circuit trip.
5	Close the circuit breaker again.

For more information about restarting following a fault, refer to Responding to a trip.

Checking the Settings

Checking settings does not require any particular precautions. The checks must be carried out by a qualified person.

Testing the Circuit Breaker

CAUTION
HAZARD OF NUISANCE TRIPPING Protection tests must be done by qualified electrical personnel. Failure to follow these instructions can result in injury or equipment damage.

When testing circuit breaker trip mechanisms, precautions must be taken:

To avoid disrupting operations.
To avoid inappropriate actions or tripping of alarms.

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 a replacement power source).

Setting the Trip Unit

WARNING
HAZARD OF NUISANCE TRIPPING OR FAILURE TO TRIP Protection setting adjustments must be done by qualified electrical personnel. Failure to follow these instructions can result in death, serious injury, or equipment damage.

Modifying trip unit settings requires a thorough knowledge of the installation and safety rules.