1、AN AMERICAN NATIONAL STANDARDNECA 402-2014 Standard forInstalling and Maintaining Motor Control CentersPublished byNational Electrical Contractors AssociationStandard forInstalling and MaintainingMotor Control CentersNECA 402-2014An AmericanNational StandardPublished byNational Electrical Contractor
2、s AssociationNOTICE OF COPYRIGHTThis document is copyrighted by NECAReproduction of these documents either in hard copy or soft (including posting on the web) is prohibited without copyright permission. For copyright permission to reproduce portions of this document, please contact NECA Standards th
3、e phase conductors are physically isolated from each other. Consult local building codes and coordinate seismic requirements for motor control centers prior to installation. In seismic locations, provide a minimum of 4000 psi concrete for foundations. Use manufacturer-recommended anchoring means, su
4、ch as stud anchors, sleeve anchors, or concrete anchor bolts.n 101. ScopeProper installation is essential to the successful operation of all motor control center components. Advance preparation and planning for installation is advisable. Request the manufacturers instruction manuals, related literat
5、ure, and drawings before the motor control center is delivered, and study this material thoroughly before installation.6.1 General Install motor control centers in accordance with contract documents, manufacturer instructions, and approved shop drawings. Install motor control center sections in fina
6、l positions, progressively leveling each section and bolting frames of shipping splits together. Secure the motor control center to walls or other supporting surfaces in accordance with manufacturer recommendations, if necessary. Do not secure motor control centers with wooden plugs driven into hole
7、s in masonry, concrete, plaster, or similar materials. Install motor control center sections starting with the most restrictive section first. If the motor control center has incoming cables or busway near or in its center, start with that vertical section first and work outwardly on each side. If t
8、he motor control center is fed from the left-most section, start from the left and work toward the right. If the motor control center is fed from the right-most section, start from the right and work toward the left. If the motor control center is close-coupled to a transformer, start at the transfo
9、rmer and work away from the transformer. Clean dirt and debris from the concrete equipment foundation and the surrounding area where the motor control center will be located before moving the motor control center into its final position. Remove shipping skids before installing the motor control cent
10、er on the foundation.6.2 Installing Vertical Sections If the motor control center sections are equipped with bottom closure plates, temporarily remove these plates. Cut holes in motor control center bottom closure plates that correspond to the conduits entering the bottom of each enclosure based on
11、that sections conduits. Saw kerfs between conduit holes in bottom closure plates for isolated phase installations where individual phase conductors are run in individual conduits, such as duct bank risers. Reinstall bottom closure plates after the vertical sections of the motor control center have b
12、een installed. Ensure that steel bottom plates are provided for motor control centers installed on combustible surfaces. Install motor control center vertical sections in sequence. Position each section carefully. Follow handling instructions in Section 4.2. Level sections with shims, if necessary,
13、and align each section with the previous section. Ensure proper alignment for joining structures and through-bus. Improper alignment of the through-bus can result in personal injury, death, and/or property loss. Lift each shipping section vertically into place using a crane, timbers, jacks, or a for
14、klift to clear embedded conduit projections above the finished concrete equipment foundation, when necessary. Remove lifting straps or slings so that vertical sections can be joined flush. Leave lifting hardware on the section if their removal is not required to join adjacent sections flush together
15、.6. Installation11 nStandard for Installing and Maintaining Motor Control Centers NECA 4026.3 Joining and Anchoring Motor Control Center Sections Open all doors or remove all panels that provide access for bolting adjacent sections together. Bolt sections together in accordance with manufacturers in
16、structions, keeping in mind that the authority having jurisdiction may require that all bolts connecting bus sections be inspected for proper torque prior to closing up the motor control center. Anchor each vertical section to the base channel or foundation to protect against bumping or shifting tha
17、t can damage interior components, conduit hubs, and cable and busway connections (see Figure 4). Anchor motor control centers for seismic conditions in accordance with contract documents and local building codes. Seal completely between the concrete foundation and the motor control center structure
18、to prevent the entry of rodents, rain, and snow.6.4 Electrical Interconnections Between Vertical Sections Vertical sections of motor control centers are electrically linked together using through-bus or cables. Through-bus splice connections are extremely important to the performance of the motor co
19、ntrol center, because these connections carry the full current intended for the operation of the motor control center. Failure to properly make through-bus splice connections can result in property damage, death, or serious injury. Ensure that each source is in phase across tie-breakers in double-en
20、ded equipment.6.4.1 Through-bus Splices Through-bus splice kits are provided by the motor control center manufacturer when more than one section is required to be electrically connected together by through-bus. The splice kits may be in separate boxes, be shipped inside the sections to be spliced, o
21、r be installed on the through-bus of one or more vertical sections. Follow the proper sequence of hardware installation, as specified in the manufacturers installation instructions. Conical washers should be installed with the convex or “top” side against the nut (see Figure 5). Torque each splice b
22、olt to the values recommended by the manufacturer. In the absence of manufacturers torque tables, terminals should be tightened in compliance with Annex I of NFPA 70. Mark each torqued connection with a permanent marker. The through-bus of some motor control centers is covered with an insulating mat
23、erial. Follow the manufacturers instructions for installing insulation on each through-bus splice connection.1.13 in(29 mm)Motor Control Center FrameSecure the motor control centerto the mounting surface usingthe holes closest to the surface.Formed Base ChannelMounting SurfaceDiameter hole in eachco
24、rner for anchoring.Figure 4: Anchoring the motor control centerFigure 5: Proper positioning of conical washersHex NutBolt HeadWasherMarked “Top”WasherMarked “Top”n 12NECA 402 Standard for Installing and Maintaining Motor Control Centers6.4.2 Cable Interconnections For cable interconnections between
25、motor control center sections, install interconnection cables between sections as shown on the manufacturers drawings. Interconnecting cables may or may not be supplied by the motor control center manufacturer. Size interconnecting cables in accordance with contract documents, manufacturer recommend
26、ations, and the NEC. Torque all connections to the manufacturers recommended values. In the absence of manufacturers torque tables, terminals should be tightened in compliance with Annex I of NFPA 70. Mark each torqued connection with a permanent marker.6.4.3 Ground Bus Splices Ground bus splice con
27、nections are provided by the manufacturer when more than one section of the motor control center is required to be electrically connected (see Figure 6). Proper installation of ground bus splice connections is essential to providing a low-impedance path to ground for temporary currents resulting fro
28、m phase-to-ground faults. At the time of delivery, ground bus splice kits may be contained in separate boxes, be installed on the ground bus of one or more sections, or be stored inside the motor control center sections. Follow the proper sequence of hardware installation, as specified in the manufa
29、cturers installation instructions. Conical washers should be installed with the convex or “top” side against the nut (see Figure 5). Torque the splice bolts to the recommended value. In the absence of manufacturers torque tables, terminals should be tightened in compliance with Annex I of NFPA 70. M
30、ark each torqued connection with a permanent marker.6.4.4 Ground Cable Connections Bond motor control center vertical sections with an equipment grounding conductor or an equivalent grounding bus sized in accordance with NEC Article 250. If the motor control center does not include a ground bus, pro
31、vide bonding between sections in accordance with NEC Article 250. Terminate equipment grounding conductors on the grounding bus or to a grounding termination point provided in a single-section motor control center. Torque all connections to the manufacturers recommended values. In the absence of man
32、ufacturers torque tables, terminals should be tightened in compliance with Annex I of NFPA 70. Mark each torqued connection with a permanent marker.6.5 Grounding and Bonding Ground and bond motor control centers in accordance with manufacturers instructions and NEC Article 250. Install conductors fo
33、r ground-fault protection systems in accordance with the manufacturers interconnection wiring diagrams. Where the motor control center contains the first disconnecting means or overcurrent protective Figure 6: Ground bus splice connections13 nStandard for Installing and Maintaining Motor Control Cen
34、ters NECA 402device of a separately-derived source, ground and bond the separately-derived source in accordance with Section 6.5.1 of this standard and NEC Article 250, where the system bonding jumper is the main bonding jumper referenced.6.5.1 Service-Entrance Equipment For ungrounded systems, inst
35、all a grounding electrode conductor from the grounding electrode system to the ground lug of the motor control center. Comply with NEC Article 250 for requirements for grounding electrode conductors. If there is no existing grounding electrode system, install a grounding electrode in accordance with
36、 contract documents, manufacturer recommendations, and the NEC Article 250. For solidly-grounded systems, install a grounding electrode conductor in accordance with NEC Article 250 from the grounding electrode at the installation site to the grounding electrode conductor connection or ground lug on
37、the motor control center ground bus (see Figure 7).Install a main bonding jumper in accordance with NEC Article 250 for motor control centers where a grounded conductor or neutral is provided. Connect the supply side of the grounded conductor to the motor control center equipment ground bus. A label
38、 on the front of the motor control center will identify the section(s) that incorporate the main bonding jumper(s). For motor control centers with multiple sources, there will be two or more main bonding jumpers to install.6.5.2 High-Impedance Grounded Neutral SystemsIn accordance with NEC Article 2
39、50, high-impedance grounded neutral systems require that the conditions of maintenance and supervision ensure that only qualified persons service the installation, continuity of power is required, ground detectors are installed on the system, and line-to-neutral loads are not served from the equipme
40、nt. Connect the system neutral conductor to ground only through the grounding impedance. Where no neutral conductor is available, install the grounding impedance between the grounding electrode conductor and the neutral derived from a grounding transformer, if so equipped. Ensure that no phase-to-ne
41、utral loads are served from high-impedance grounded systems.Install fully insulated neutral conductors sized for the maximum current rating of the grounding impedance, but not less than 8 AWG copper or 6 AWG aluminum or copper-clad aluminum. The conductor connecting the neutral point of the groundin
42、g resistor or transformer to the grounding impedance is permitted to be installed in a separate raceway. Install an unspliced equipment bonding jumper from the first system disconnecting means or overcurrent protective device to the grounded side of the grounding impedance. Size the equipment bondin
43、g jumper in accordance with NEC Article 250 where the grounding electrode conductor connection is made at the grounding impedance, or with the same ampacity as the neutral conductor in Section 6.5.1 where the grounding electrode conductor is connected at the first system disconnecting means or overc
44、urrent protective device. Connect the grounding electrode conductor at any point from the grounded side of the grounding impedance to the equipment grounding Figure 7: Ground lugn 14NECA 402 Standard for Installing and Maintaining Motor Control Centersconnection at the service equipment or first sys
45、tem disconnecting means.6.6 Installing Conduits Install top- and side-entry conduits after motor control center installation is complete. Route conduits entering the motor control center in accordance with conduit entry drawings provided by the manufacturer for each section of the motor control cent
46、er to prevent cables and conductors from interfering with live bus or structural members. Ensure that the maximum projection of embedded conduits and fittings is 76 mm (3 in.) or less above concrete equipment foundation in accordance with the NEC. Bond all conduits, stubs, and ring connectors to the
47、 enclosure in accordance with the manufacturers instructions.6.7 Installing Cables and Conductors To prevent cracking or freezing of the insulation, install conductors at ambient temperatures above freezing. As an alternative, use conductors that are suitable for installation at temperatures below f
48、reezing. Verify that termination lugs are compatible with conductors prior to installing cables and conductors. Install the most restrictive set of conductors first. Unless installing an isolated phase arrangement, pass all phase and grounded conductors of the same circuit through the same metal ope
49、ning together, as required by NEC Article 300, to prevent inductive heating within the motor control center. Ensure that cable pulling lubricants do not drip or come into contact with overcurrent protective devices or bus bar plating. Use the largest practical bending radii to avoid damaging conductor insulation. Train and form conductors to minimize stress on terminals, minimize sag, and prevent physical damage or overheating. Check manufacturer instructions to determine which connections require sag to permit future maintenance on the motor control center.
