Feeder Details:

1.5.1 MCC ‘s shall be provided with one incomer and required number of outgoing feeder modules.

1.5.2 Atleast one outgoing feeder of each rating shall be provided as spare in the switch board.

1.6 Construction:

1.6.1 MCC shall be metal enclosed, fully drawout, indoor, floor mounted modular type, dust and vermin proof of uniform height of not more then 2450 mm, easily extensible on both sides having switch board designation indicating labels. The IP degree of protection shall not be less than IP 42.

1.6.2 The external paint shade shall be -631 of IS –5. 1.6.3 MCC shall be single/double front execution.

1.6.4 The frame of individual panel shall be fabricated using pressed and shaped cold rolled sheet steel of adequate thickness or by using suitable mild steel structural sections. The sheet steel used for panels shall be minimum 14 SWG CRCA except that the doors and covers may be made of 16 SWG CRCA. Stiffeners shall be provided to increase stiffness of large doors and covers.

1.6.5 Switchboard shall be provided with integral base frame for each vertical panel. The switchboard integral base frame shall be suitable for directly bolting with the help of foundation bolts and shall be suitable for track welding to the floor embedded channels.

1.6.6 All openings, covers and doors shall be provided with neoprene gaskets. Blanking plates shall be provided for all sizes of modules to covers the openings in the event of withdrawing the feeder modules.

1.6.7 All hardware shall be corrosion resistant. All joints and connections of the panel members shall be made by high quality cadmium plated steel bolts, nuts and washers, secured against loosening. Star washers shall be used to ensure effective continuity.

1.6.8 Suitable removable type lifting hooks shall be provided, and the hooks when removed shall not leave any opening in the panel.

1.6.9 MCC shall be divided into distinct vertical sections of: (a) Uniform height

(b) Completely enclosed metal busbar compartment running horizontally. (c) Individual feeder modules in multitier arrangement.

(d) Enclosed vertical bus bars serving all modules in vertical section. The vertical busbar shall be sleeved and provided with anti-tracking barriers as an integral part of bus bar zone.

(e) Vertical cable alley covering entire height and minimum 200 mm wide. (f) A horizontal separate enclosure for all auxillary power and control bus, if

required.

(g) Each vertical section shall be equipped with space heater with thermostat. (h) Cable alley shall be provided with suitable hinged doors.

(i) Metal sheet shall be provided between two adjacent vertical panels running upto full useful heights of switchboard. In the cabling chamber shrouds shall be provided on the side of vertical busbars.

1.6.10 Panels shall be suitable for bottom entry of cables

1.6.11 Rear of single front switch board shall be provided with removable panels. 1.6.12 All doors shall be with concealed type hinges and captive screws.

1.6.13 Auxiliary busbars each of minimum size 18 sq.mm copper shall be provided for space heater supply, control supply. Tee-off connectors shall be used for distributing supply to each vertical panel. Rubber grommets shall be used for all wire entries to make panel dust and vermin proof.

1.6.14 Busbars shall be of high conductivity aluminum (E91E) supported on insulators made of non-hygroscopic, non-inflammable materials with tracking index equal to or more than 600mm as per IEC-112. Such as glass reinforced phynolic material or cast resin. Bus bar joints shall be shrouded with moulded epoxy shrouds. The main busbar shall have uniform current ratings throughout their length. The current rating of the neutral

shall be half that of the phase busbars. Removable neutral links shall be provided on feeders to permit isolation of the neutral busbar.

1.6.15 All busbars, bus joints and supports shall be capable of withstanding dynamic and thermal stresses of the specified short circuit currents for 1 seconds. Only zinc passivated or cadmium plated high tensile strength steel bolts, nuts and washers shall be used for all busbar joints and supports. The short circuit capacity of the neutral busbars shall be in line with IS 13947.

1.6.16 All busbars shall be insulated with heat shrunk PVC sleeves of 1100V grade. Red, yellow and blue colour shall be used for phase busbars and black colour for neutral busbars. Joints shall be shrouded properly.

1.6.17 Minimum clearance between live parts, between live parts/neutral to earth shall be 19mm. However clearances at components shall be as per individual standards.

1.6.18 Interconnections between main busbars and individual units shall be made by vertical aluminium busbars of adequate rating. These interconnections and the vertical busbars shall be compartmentalised and fully shrouded. Busbars shall be of uniform cross- section and the vertical size of busbars shall not be less than 50 * 10 mm. Per phase. All joints surfaces at aluminium to copper joints shall be silver/tin plated, alternatively bimetal washers may be used. Minimum size of busbars for starter/feeder power connection above 100 Amp rating shall be 20X6 mm of Aluminium.

1.6.19 Inside the switchboard wiring for power control etc shall be done with BIS approved 660 volts grade PVC insulated copper conductors. All control wiring shall be enclosed in plastic channels or neatly bunched together. Conductors of cross section 1.5sq.mm shall be used for control circuits with control fuse rating of 10 amps or less and 2.5sq.mm for other circuits and CT wiring.

1.6.20 Each wire shall be identified at both ends by PVC ferrules.

1.6.22 A minimum of 10% spare terminals shall be provided on each terminal block. Conductors shall be terminated with adequately sized compression type lugs. Clamp type terminals for direct conductor termination shall be acceptable for wires upto 10sq.mm size and bolted type terminals with crimping type copper lugs shall be provided for all outgoing cable connections larger than 10sq.mm.

1.6.23 All vertical panels shall be connected to a tinned copper earth busbar running throughout the length of the switchboard. The min earth bus size shall be 300sq.mm tinned copper. All doors and movable parts shall be earthed using flexible copper connections to the fixed frame of the switchboard. All non-current carrying metallic parts of the mounted equipment shall be earthed. Minimum 4 nos. of 10-mm dia bolts with nuts shall be provided on the earth bus for termination of fourth core per vertical panel.

1.6.24 A nameplate with the switchboard designation shall be fixed. A separate nameplate giving the details of each compartment of bus section shall be provided.

1.6.25 Nameplate shall be provided for each equipment (lamps, pushbuttons, relays, contactors etc) mounted on the switchboard. Special warning plates shall be provided on removable cover or doors giving access to cable terminals and busbars. Identification tags shall be provided inside the panels matching with those shown on the circuit diagram.

1.6.26 Engraved nameplates shall be of 3 ply lamicoid sheets or anodised aluminium. And they should be fastened to the panels by screws and not by adhesives.

1.6.27 The nameplate for feeder compartments shall be in two parts. One part shall have details pertaining to the other part shall be removable and shall contain details regarding the drives/equipments controlled by particular module.

1.6.28 All metal surfaces shall be thoroughly cleaned and degreased to remove millscale, rust, grease and dirt. Fabricated shall be pickled and then rinsed to remove any trace of acid. The undersurface shall be prepared by applying a coat of phosphate paint and

coat of yellow zinc chromate primer. The under surface shall be made free from all imperfections before undertaking the finishing coat.

1.6.29 After preparation of the under surface, the switchboard shall be spray painted with two coats of epoxy based final paint or shall be powder coated. The finished panels shall be dried in stoving ovens in dust free atmosphere. Panel finish shall be free from imperfection like pinholes, orange peels, runoff paint etc.

1.6.30 All unpainted steel parts shall be cadmium plated or suitably treated to prevent rust formation. If these parts are moving elements then they shall be greased.

1.6.31 MCC shall be designed such that all component equipment and bus bars operate satisfactory with out exceeding their respective maximum permissible temperature limits of 85 deg C.

1.6.32 The bus bar rating of the 415 V MCC shall be rated for full load current plus 20% margin rounded off the next standard rating.

1.6.33 All identical equipments and corresponding parts shall be fully interchangeable, without requiring structural modification.