Switchgear & Motor Control Centers

Switchgear and motor control centers (MCCs) distribute and control large amounts of electrical power in plants, hospitals, data centers, commercial buildings and utilities. A fault inside can release an arc flash with temperatures hotter than the sun’s surface, a pressure blast and molten metal. Only qualified people, using the right procedures and protective equipment, should work on or near them.

• Industrial Electricians
• Maintenance Techs
• Facility Managers
• Commissioning Teams

What they are

• Switchgear is an assembly of circuit breakers, switches, fuses, buses and protective relays in a metal enclosure, which controls and protects power distribution. Low-voltage switchgear works up to 1,000 volts, and medium-voltage switchgear works above that (commonly 5 to 38 kilovolts).
• Switchboards and panelboards are related, simpler distribution equipment.
• Motor control centers are cabinets with plug-in or fixed “buckets” (units) holding starters, drives, breakers and controls for motors, sharing a common bus. See Breakers & Fuses.
• Draw-out breakers can be racked in and out of cubicles, connecting or disconnecting from the bus.
• Many installations also include transformers, generators and transfer switches. See Transformers and Standby Generators.

Main hazards

• Arc flash and arc blast: a fault produces intense heat, light, pressure and shrapnel. Burns can be fatal at several feet. See Arc Flash and Arc Flash PPE Categories.
• Electric shock and electrocution from contact with energized parts, especially at medium voltage. See Electrical Injuries.
• Stored energy: breaker closing springs, charged capacitors and control circuits that can operate unexpectedly. See Capacitors.
• Back-feed and multiple sources: tie breakers, generators, solar, UPS and other feeds can energize gear that looks off.
• Heavy equipment: breakers weigh hundreds of pounds and can fall or crush hands when racked or moved. See Rigging Basics.
• Mechanical hazards: springs, moving mechanisms and closing doors.
• Poor maintenance: dust, moisture, loose connections, damaged insulation and worn mechanisms make failures more likely. See Electrical Equipment Maintenance (NFPA 70B).
• Unqualified entry and bad habits such as leaving doors open, removing barriers or using the wrong tools.

Rules and information you need

• NFPA 70E (Standard for Electrical Safety in the Workplace) sets requirements for safe work practices, risk assessment and arc flash protection. OSHA enforces related requirements in 29 CFR 1910 Subpart S. See Electrical Safety Programs and National Electrical Code (NEC).
• Equipment labels must show nominal voltage, and arc flash and shock information (incident energy or PPE category, boundaries), as the NEC and 70E require. Read the label before you open the door.
• One-line diagrams, short-circuit and coordination studies and arc flash studies should be current. Don’t rely on out-of-date drawings, and update after changes.
• Working space: the NEC requires clear working space in front of equipment, generally at least 3 feet deep at lower voltages (more at higher voltages), a minimum width, headroom and a clear path out. Don’t store anything in this space. See Panel Clearance.
• Only qualified persons may work on or near exposed energized parts. See Qualified vs. Unqualified Persons.

Safe work practices

• Prefer to work de-energized. Energized work is allowed only when it is infeasible to shut off, such as for troubleshooting or when shutdown creates greater hazard, and it requires an energized work permit and risk assessment. See Energized Work Permits.
• Establish an electrically safe work condition: identify all sources, open and lock out each, verify with a tester, ground where required and release stored energy. See Lockout/Tagout and Absence-of-Voltage Testing.
• Hold a job briefing covering hazards, boundaries, roles, emergency steps and PPE.
• Wear the right PPE. Arc-rated clothing and face shield or hood, hard hat, safety glasses, hearing protection, voltage-rated gloves with protectors and leather work shoes, matched to the arc flash label or the 70E tables. See Rubber Insulating Gloves and Flame-Resistant Clothing.
• Keep doors closed and latched during normal operation, and limit who opens equipment. Racking, switching and operating with the doors closed, from a distance or with remote operators, greatly reduces risk. Many sites require remote racking for energized breakers.
• Racking breakers: follow the maker’s procedure, confirm the breaker is open, use the right tool and stay out of the line of fire. Wear PPE rated for the risk, and don’t rack a breaker on a bus that is faulted or suspect.
• Use rated tools and meters, with the correct category rating, and inspect them. See Test Meters.
• MCC buckets: don’t pull or insert energized buckets unless the procedure and PPE allow it. Use the disconnect handle interlocks, and never defeat them.
• Never bypass interlocks, barriers or protective devices, and don’t leave panels open or bus exposed unattended.

Inspection and maintenance

• Follow a documented maintenance program (NFPA 70B), with cleaning, tightening, lubrication, breaker testing, relay testing and insulation tests at set intervals. Poor maintenance is a major cause of arc flash events.
• Infrared thermography finds hot connections. Use viewing windows, or have trained people inspect with doors closed where possible. If panels must be opened for scanning, treat it as energized work with proper PPE.
• Check environmental conditions: keep rooms clean, dry and ventilated, and keep out dust, pests and moisture.
• Test and calibrate protective relays, breakers and arc-flash reduction systems as required.
• Document all work, findings and changes, and update labels and diagrams.
• Reduce hazards by design: arc-resistant switchgear, maintenance mode settings, current-limiting fuses and remote operation lower incident energy.

Emergencies

• If someone is shocked or burned, don’t touch them until power is off or they are clear, and call 911. See Electric Shock Response.
• Know the location of emergency shutoffs, and have trained staff and rescue plans.
• Report equipment faults, smells, noises, heat and arcing immediately, and don’t re-energize after a fault until a qualified person inspects the gear.

Switchgear and MCC checklist

• I am a qualified person, and I read the arc flash and shock labels before opening anything
• Work is done de-energized where possible; locks, tests and grounds are in place and verified
• I wear the arc-rated clothing and PPE called for, and use rated tools and meters
• Working space is clear, doors are closed during operation and interlocks are never defeated
• Breakers are racked by procedure, preferably remotely, with a safe stance
• Equipment is maintained on schedule, and diagrams and labels are current

Last updated: October 5, 2026