How to Safely Change a Commercial Building's Main Circuit Breaker

Introduction

Changing a commercial building's main circuit breaker is a complex and potentially dangerous task that should only be performed by licensed electricians. However, with proper planning and precautions, it can be done safely. This article will provide an in-depth guide on how to safely change a commercial building's main circuit breaker.

Reasons for Changing the Main Breaker

There are several reasons why you may need to change the main circuit breaker in a commercial building:

• Upgrading to a higher amperage breaker - If additional electrical load has been added to the building, the existing breaker may not be able to handle the increased power demand. Upgrading to a higher amperage breaker allows for more power to be safely distributed.

• Replacing an old or faulty breaker - Old breakers can become faulty over time. Replacing the main breaker with a new one ensures optimal performance and safety.

• Changing from fuses to breakers - In older buildings, the main electrical panel may still be using old-style fuses. Upgrading to circuit breakers provides better overcurrent protection.

• Service change or upgrade - When increasing the electrical service to the building, the main breaker will need to be replaced to match the new service size.

Preparation

Changing the main breaker requires careful preparation and planning:

• Obtain permit - Most jurisdictions require an electrical permit for replacing a commercial building's main breaker. The licensed electrician should obtain this permit.

• Disconnect all power - All power to the building must be completely shut off at the utility connection before any work can be done. The electrician must coordinate with the utility company to kill power at the appropriate time.

• Verify power is off - Before doing any work, the electrician should double-check that all power is disconnected using a non-contact voltage tester. Verify that all circuit breakers are off and that all fuses are removed.

• Gather necessary tools - Wire cutters, strippers, voltmeter, phase rotation meter, clamp meter, and other electrical hand tools will be required. Make sure they are in good condition before starting work.

• Have new breaker on hand - The new upgraded main breaker should be on site and ready to install. Make sure it is compatible with the building's electrical system.

• Clear access to panel - The area around the main electrical panel should be clear of obstructions to allow easy access for the electrician.

Step-by-Step Procedure

Once all preparation is complete, the main breaker can be changed out by following these key steps:

1. Remove old breaker

• Loosen and remove any fasteners or retaining screws holding the old main breaker in place.
• Carefully pull the breaker straight out of the panel to disconnect it.

2. Install new breaker

• Inspect the panel bus bars where the new breaker will connect. Clean any corrosion or debris.
• Insert the new breaker into the corresponding slot, ensuring it aligns properly and the retaining clips engage.
• Tighten all retaining screws and fasteners to secure the new breaker.

3. Connect feeder wires

• Use wire cutters to remove existing main feeder wires from the old breaker.
• Strip insulation on wire ends and attach them to the new breaker terminals in the correct positions.
• Tighten terminal screws securely and double-check connections.

4. Verify proper operation

• With the panel still de-energized, switch the new main breaker on and off to verify smooth operation.
• Use a multimeter to check for continuity through the breaker.
• Carefully inspect the breaker installation to ensure all connections are tight.

5. Restore power

• Notify the utility company to re-energize the service to the building.
• When power is restored, switch the main breaker on and check for proper voltage readings.
• Methodically turn on each individual circuit and verify proper operation throughout the building.

Safety Precautions

• Wear personal protective equipment at all times, including rubber insulating gloves and sleeves.
• Use properly insulated tools and test equipment.
• Take steps to avoid arc flash hazards, such as wearing arc-rated clothing.
• Follow all electrical safety procedures such as lockout/tagout.
• Work with a partner for observation and assistance.
• If at any point conditions seem unsafe, stop work immediately.

Replacing a commercial building's main circuit breaker requires expertise and safety vigilance. But when done properly by qualified electricians, it can upgrade and improve the electrical system safely and reliably. Let me know if you have any other questions!