When the distribution box is installed on the wall, it should be fixed with split bolt (expansion bolt). The bolt length is generally the sum of the embedded depth (75-150 mm), the thickness of the box bottom plate, the thickness of the nut and washer, plus the "head allowance" of about 5mm. Check for proper IP/NEMA ratings and material quality. The fixing method should be firm and reliable to avoid movement or tilting of the box due to vibration or. 4 KV Substation of the ratings indicated above. The body of the boxes shall have sufficient re- enforcement with suitable size of channels keeping a provision for fixin andle conforming to general. The most common size screw to use in an electric box is a 6-32 flathead screw. For heavier applications, like ceiling lighting and ceiling fans, an 8-32 screw will work better.
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