ENCLOSURES

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2.2 ENCLOSURES
2.2.1 SELF-CONTAINED FLOOR MOUNTED CUBICLE
SWITCHBOARDS
The framework of the switchboard shall be fabricated from rolled steel sections of thickness not less than 2.5 mm and shall be self-supporting when assembled, uniform in height and depth from front to back. The rigid construction shall be designed to withstand without any sag, deformation or warping, the loads likely to be experienced during normal operating, maintenance or maximum fault condition.
The front shall be provided with covers/doors of box formation. The rear shall be provided with hinged removable doors of box formation. The rear doors shall be of double-leaf type with rebated edges and each leaf should preferably not be wider than 450 mm. Each leaf of door shall have 2 pairs of approved hinges. The door shall be fitted with approved type of surface-mounted espagnolette or cremone bolts complete with approved locking device operated by a satin chrome lever handle at the centre fixing. The top and sides shall be of removable panels.
Cover plates with openings for cable entry shall be provided at the base of the switchboard. All panels, covers and doors shall be fabricated from sheet steel of thickness not less than 2.0 mm and so constructed as to provide a clear, flush and pleasing appearance. The panels, covers and front doors shall be secured to the enclosure by means of chromed type of screws with cylindrical knurled head complete with retaining clips. Welded cross struts shall not be used.
The switchboard shall be dust and vermin proof. All covers and doors shall be provided with grommets and dust seals to exclude dust and dirt. Louvres or ventilation vent with filter shall be provided at the sides and back for adequate ventilation. Precaution shall be taken to prevent overheating due to hysteresis and eddy current. All edges shall be rounded. Serrated star washers shall be fitted to ensure satisfactory earthing of the front cover.

The switchboards shall be of Form 2b separation where the busbar separation from the switchgears and the incoming and outgoing terminals is achieved by metallic or non-metallic rigid barriers or partitions. All switchgears shall be mounted so as to give adequate clearance for cable and busbar connections.
Switchgears shall be mounted on insulation runners where connected to busbars and on steel supports where cable connection are made. The insulation runners shall be of minimum 10 mm thickness and mounted on steel support or back panel of the enclosure whichever is more appropriate.
Cables connection between the busbars and the switchgears shall be neatly arranged and mounted on cable runner. The terminals of the switchgears for external cable connections shall be at least 200 mm above the base of the switchboards and, moreover, so placed that the cables can be easily connected to them. Withdrawable type of switchgears shall be mounted on the framework assembly, including the runner rails and fixed rear isolation contacts, which shall be supplied as a part of the switchgear assembly. Each withdrawable switchgear shall be housed in its own compartment with rear connected busbars.
All indicating instrument which need to be read by the operator shall not be located higher than 2 m above the base of the switchboard. All operating devices such as handle, push buttons, etc., shall be located at such a height that they can easily be operated, and in general, the centreline shall not be higher than 2 m above the base of the switchboard. In the case where building automation devices, transducers and relays are provided, they shall be separately housed in a compartment of the section of the switchboard. All wiring from the devices, transducers and relays shall be neatly arranged and connected to the terminal blocks with removal links mounted on rail. Terminals shall be identified and labelled in accordance with IEC 60445.
Where surge protection device is specified, the device and its associated equipment shall be housed in a separate compartment at immediate lower subsection where the incoming switchgear is connected. A lockable tool compartment with keys and opening handle shall be provided at the lowest subsection of the switchboard. The switchboard shall undergo de-rusting treatment, anti-rust treatment with the exterior finished with epoxy dry-powder and oven baked semi-gloss enamel grey and interior finished matt white. The switchboard shall be bolted to mild steel channel base or over concrete trench. The channel shall be anti-rusted and painted with a primer.

 


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