Substation Rooms, and Buildings

A motor control center (MCC) contains a number of enclosed motor control switches and breakers on a common power bus. MCCs should be of non- 

Wall penetrations for cables and conduits should be sealed with an approved fire retardant sealant. If conduit is used that subsequently passes through flammable areas, appropriate conduit seals must be used at the MCC terminus. 

If the MCC will be located within an electrically classified area, the ventilation system must be designed, operated and maintained to create a positive pressure inside the MCC building and the air intake located outside of the electrically classified area. The MCC should be equipped with smoke detectors and alarmed to a constantly attended location. CO2 fire extinguishers are the suggested protection for MCC rooms. The storage of combustible materials inside an MCC must be prohibited. 

I n larger MCCs, if the combustible loading gets extensive, then passive fire protection, e.g., fire-resistant cables or passive fire protection should be considered. The practices of using multiple tiers of cable trays or stripping the outer jacket insulation (to make the cable easier to handle after it enters the room or cabinet) are not recommended. 

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