power distribution - Siemens

Motor Control CentersWiring ClassificationsSiemens MCC’s are available as eitherClass I or Class II assemblies utilizing eitherType A, Type B, or Type C wiring as definedin NEMA ICS18-2001(3.1) and NEMAICS18-2001(3.3). Below are the NEMAclass and type definitions:Class I — Independent Units (NEMAICS18-2001(3.2.1))Class I motor control centers shall consistof mechanical groupings of combinationmotor control units, feeder tap units, otherunits, and electrical devices arranged in aconvenient assembly. The manufacturershall furnish drawings that include:a. Overall dimensions of the motor controlcenter, identification of units and theirlocation in the motor control center,locations of incoming line terminals,mounting dimensions, available conduitentrance areas, and the location of themaster terminal board if required (Type Cwiring only).b. Manufacturer’s standard diagrams forindividual units and master terminal boards(Type C wiring only) consist of one or moredrawing(s) that:1. Identify electrical devices.2. Indicate electrical connections.3. Indicate terminal numberingdesignations.Note: When a combination schematic and /or wiring diagram for a unit is suppliedshowing optional devices, the manufacturershall provide information to indicate whichdevices are actually furnished.Class II — Interconnected Units (NEMAICS18-2001(3.2.2))Class II motor control centers shall be thesame as Class I motor control centers withthe addition of manufacturer furnishedelectrical interlocking and wiring betweenunits as specified in overall control systemdiagrams supplied by the purchaser. Inaddition to the drawings furnished for ClassI motor control centers, the manufacturershall furnish drawings that indicate factoryinterconnections within the motor controlcenter.Class I-S and II-S — Motor ControlCenters With Custom DrawingRequirements (NEMA ICS18-2001(3.2.3))Class I-S and II-S motor control centersshall be the same as Class I and II exceptcustom drawings shall be provided in lieuof standard drawings as specified by theuser. Examples of custom drawings are:▪ Special identifications for electricaldevices▪ Special terminal numbering designations▪ Special sizes of drawingsThe drawings supplied by the manufacturershall convey the same information asdrawings provided with Class I and II motorcontrol centers, additionally modified asspecified by the user.Types of Wiring — NEMA ICS18-2001(3.3.1)Type A (NEMA ICS18-2001 (3.3.1.1))User field wiring shall connect directly todevice terminals internal to the unit andshall be provided only on Class I motorcontrol centers.Technical / DimensionsType B (NEMA ICS18-2001(3.3.1.2))a. Type B user field load wiring forcombination motor control units size 3 orsmaller shall be designated as B-D or B-T,according to the following:▪ B-D connects directly to the deviceterminals, which are located immediatelyadjacent and readily accessible to thevertical wireway.▪ B-T connects directly to a load terminalblock in, or adjacent to, the unit.b. Type B user field load wiring forcombination motor control units larger thansize 3, and for feeder tap units, shallconnect directly to unit device terminals.c. Type B user field control wiring shallconnect directly to unit terminal block(s)located in, or adjacent to, each combinationmotor control unit.Type C (NEMA ICS18-2001(3.3.1.3))User field control wiring shall connectdirectly to master terminal blocks mountedat the top or bottom of those verticalsections that contain combination motorcontrol units or control assemblies whichshall be factory wired to their masterterminal blocks. User field load wiring forcombination motor control units, size 3 orsmaller, shall connect directly to masterterminal blocks mounted at the top orbottom of vertical sections. Motor controlunit load wiring shall be factory wired to themaster terminal blocks. User field loadwiring for combination motor control unitslarger than size 3, and for feeder tap units,shall connect directly to unit deviceterminals.15MOTOR CONTROLCENTERSIAIB-TIIBIICIB-DICSiemens Power Distribution & Control, SPEEDFAX 2007-2008 Product Catalog 15-7