6.2 Commercial Electrical Systems - Commercial Electrical Systems Explained

Key Concepts

Commercial electrical systems are designed to meet the power needs of businesses, offices, and other commercial establishments. These systems are typically more complex and require higher power capacities than residential systems. Key concepts include:

• Service Entrance: The point where electrical power enters the building.
• Main Service Panel: The central distribution point for electrical power within the building.
• Subpanels: Additional distribution panels that branch off from the main service panel.
• Branch Circuits: Individual circuits that supply power to specific areas or devices.
• Grounding and Bonding: Safety measures to prevent electrical hazards.
• Emergency and Standby Power Systems: Backup power sources for critical operations.

1. Service Entrance

The service entrance is the point where electrical power enters the building from the utility company. It includes the main service drop, which is the overhead or underground cable that connects to the building, and the service equipment, which includes the main disconnect and overcurrent protection devices.

Example: A commercial building's service entrance might include an overhead service drop connected to a weatherhead, which then connects to the main disconnect located in the main service panel.

Analogy: Think of the service entrance as the front door of a house, where all visitors (electrical power) enter.

2. Main Service Panel

The main service panel is the central distribution point for electrical power within the building. It houses the main disconnect and circuit breakers or fuses that protect the branch circuits. The main service panel is typically located near the service entrance to minimize the length of the main power feed.

Example: A large office building might have a main service panel with multiple circuit breakers, each assigned to different areas or systems within the building.

Analogy: The main service panel is like the heart of the electrical system, distributing power to various parts of the body (building).

3. Subpanels

Subpanels are additional distribution panels that branch off from the main service panel. They are used to distribute power to specific areas or systems within the building, such as individual floors, departments, or large equipment. Subpanels help to manage the load and simplify the distribution of power.

Example: A multi-story office building might have a subpanel on each floor to distribute power to the offices, lighting, and other electrical needs on that floor.

Analogy: Subpanels are like smaller arteries branching off from the main artery (main service panel), delivering power to specific parts of the body.

4. Branch Circuits

Branch circuits are individual circuits that supply power to specific areas or devices within the building. Each branch circuit is protected by a circuit breaker or fuse in the main service panel or subpanel. Branch circuits are designed to handle specific loads and are labeled according to their function.

Example: A branch circuit might supply power to a group of office outlets on a specific floor, or to a large piece of equipment in a manufacturing facility.

Analogy: Branch circuits are like the veins and capillaries of the electrical system, delivering power to individual cells (outlets and devices).

5. Grounding and Bonding

Grounding and bonding are safety measures to prevent electrical hazards. Grounding involves connecting electrical systems to the earth to provide a safe path for fault currents. Bonding connects all non-current-carrying metal parts to create a low-impedance path for fault currents.

Example: A commercial building's electrical system might include grounding electrodes connected to the main service panel and bonding conductors connecting all metal parts of the electrical system.

Analogy: Grounding and bonding are like the immune system of the electrical system, protecting it from harmful electrical currents.

6. Emergency and Standby Power Systems

Emergency and standby power systems provide backup power to critical areas or systems in the event of a power failure. Emergency power systems, such as emergency lighting and exit signs, are required by code to operate during a power outage. Standby power systems, such as generators, provide backup power to critical operations.

Example: A hospital might have an emergency power system that automatically switches on to provide power to life-support equipment and essential lighting during a power outage.

Analogy: Emergency and standby power systems are like the body's emergency response system, ensuring critical functions continue during a crisis.

Understanding these key concepts is essential for designing, installing, and maintaining commercial electrical systems. By mastering these elements, construction electricians can ensure that commercial buildings have safe, reliable, and efficient electrical systems.