Select the size number of earthing for an Industry – How?
Heavy industrial motors say 50 kw and above to run certain processing machines in sugar, Paper, steel, textile, and heavy industries , arc/blast furnaces etc, EOT cranes,Passenger /goods lifts, material equipment i.e conveyers
The work shop machinery less than 50 kw including FHP motors i.e lathe machines, drilling machines, grinding machines, Hack saw machines, shearing, cutting and bending machines, power /hydraulic presses, injection molding machines. Portable tools and other such light machinery. and water pumps
The CNC machines, Speed drives (Vfd etc) and other technological advanced computerized equipment
Air conditioning plants , ventilation equipment etc
The Individual body earthing is recommended for EOT cranes, Lifts, arc/Blast furnaces, conveyers systems.
Other motors can be connected in parallel with common main earthing , Precautions must be taken that distance covered is not vey long so that circuit impudence is not increased causing high earth resistance . In such case the the experience of the engineer in charge is very important to decide on the distance. We can recommend more than two conductors to run in parallel with proper termination of joint and good quality of nuts, bolts, spring washers and flat washers.. To avoid rusting of joints it is suggested to use the stain steel hardware and good quality of fasteners to avoid loose /weak joints.
The earthing for the fixtures of the lighting equipments can be earthed in parallel with single earthing keeping the precaution termination of joints and taking that weak /loose joints are strictly avoided. It is not necessary to provide double earthing or two earthing in parallel simply because engineering department cannot ensure reasonably strong and electrically good joints.
Cnc machines and other computerized equipment as per manufacturers’ recommendation. One must use separate earthing for the body and neutral . neutral earthing is is Compusory for controlling FLOATING neutral voltages which might other vise damage the electronic PCB `s in the equipment.
For DG sets , transformers ,and severs /ups systems 2 nos. earthing are necessary for body and neutral . The is 3043 -1987 is clear on this concept.
The separate single earthing is necessary for the body and neutral of the protective equipment.
