Section 1—About the Model 6 Motor Control Center
Motor control centers (MCCs) provide the most suitable method for grouping electrical motor control and other related devices in a compact, economical, and free-standing installation. A motor control center is made of standardized vertical sections consisting of totally enclosed, dead front, free-standing structures bolted together. These sections support and house control units, a common bus bar for distributing power to the control units, and a network of wireways and conductor entrance areas to accommodate outgoing load and control wires.
The control units consist of components such as combination motor starters, branch feeder devices, and lighting panelboards. Each is mounted in an individual, isolated compartment having its own cover. When frontofboard unit arrangement is selected, all units are mounted on the front side of the MCC. A 15 in. (381 mm) or 20 in. (508 mm) deep section is provided for front-of-board mounting. The standard MCC width is 20 in. (508 mm) with a 4 in. (102 mm) wide vertical wireway.
An optional 25 in. (635 mm) wide section with a 9 in. (229 mm) wide wireway is also available. Larger sections are available for mounting larger equipment. When a back-to-back arrangement is selected, the units are mounted on both the front and rear of 31 in. (787 mm) or 41 in. (1041 mm) deep structures. Approximately 1 in. (25 mm) of space is between backtoback sections. The standard height of all MCC structures is 91.5 in. (2324 mm) without the 3 in. (76.2 mm) lifting angle.
Model 6 MCCs are available with an arc-rated option that provides an arc containment rating tested per ANSI C37.20.7-2007 guidelines. Additional reinforcement and pressure relief features are added to the Model 6 MCC to meet the arc containment rating. Refer to ANSI C37.20.7-2007 for the specific test requirements to which the arc-rated Model 6 MCC has been subjected.
The arc-rated Model 6 MCC can provide enhanced arc containment in case of an arcing fault inside the MCC. This is a valuable feature along with other arc flash enhancements available with Model 6 MCCs. Contact your local Schneider Electric representative for more information on Model 6 MCC arc flash options.
A Model 6 MCC with the arc-rated option includes a label (Model 6 MCC 100 ms Arc-Rated Option Label and Typical Location on Enclosure) which states the performance and requirements necessary to maintain the rating. The arc containment rating is applicable to the front, sides, and rear of the MCC (defined as Type 2 in ANSI C37.20.7-2007).
This instruction bulletin contains specific instructions on maintaining, modifying, and expanding an arc-rated Model 6 MCC. These instructions must be followed to maintain the arc containment rating of the MCC. To achieve the labeled arc containment rating, the additional 100 Millisecond, Arc-Rated MCC, Upstream Over-Current Protection Device (OCPD) Requirements must be met.