MCC Remote Racking: Removing the Worker from the Hazard
Why racking a Motor Control Center (MCC) bucket or breaker is the most dangerous task in the switchroom, and how remote racking saves lives.
The Danger of the Crank
Operating an industrial electrical system from the front panel is generally safe. The extreme hazard arises when technicians have to physically interact with the live bus, most commonly when “racking” (inserting or removing) a draw-out circuit breaker or a Motor Control Center (MCC) bucket.
During the racking process, the mechanical stabs of the bucket are sliding onto the energized vertical bus bars. If there is a slight misalignment, a compromised stab, a tool left inside the bucket, or simply mechanical failure of degraded insulation, an arc flash can initiate instantly.
Because the worker is standing directly in front of the bucket turning a crank or pushing it in, their chest and face are squarely in the line of fire. The blast wave, molten copper, and extreme heat are directed straight at them.
Engineering Controls vs. PPE
Historically, the only defense during racking was donning a heavy, restrictive arc flash suit (e.g., 40 cal/cm² Category 4 PPE). However, PPE is the last line of defense. It does not prevent the incident; it only attempts to limit the burns to a survivable level. It does little to protect against the massive concussive blast wave.
The hierarchy of controls dictates that we should try to eliminate the hazard or use engineering controls before relying on PPE.
Remote Racking: Distance is Safety
Remote racking systems are the ultimate engineering control for this hazard. These systems physically attach a motorized actuator to the racking mechanism of the switchgear or MCC. The technician steps outside the arc flash boundary—often 30 to 50 feet away, or entirely outside the switchroom—and operates the racking process via a pendant or wireless controller.
If a catastrophic failure occurs while the bucket is engaging the bus, the switchgear might be destroyed, but the technician is entirely unharmed.
Actionable Takeaways
- Advocate for Remote Racking. If your facility requires frequent racking of older MCCs or medium-voltage switchgear, budget for portable remote racking robots or actuators. They are cheaper than a single injury.
- Stand to the side. If remote racking is not available and manual racking is required, never stand squarely in front of the cubicle. Stand to the side (the “hinge side” if a door is present), turn your body, and operate the crank with your arm extended to minimize exposure to the blast path.
- Do not bypass interlocks. MCC buckets are designed with mechanical interlocks preventing them from being racked while the breaker is closed. Never defeat these interlocks to speed up a job.