Grounding equipment or just a conductor?

[ARIKSON ESPINAL]

I've heard that 90% of Lightning damages can be eliminated if the electrical system is properly grounded. However, a current path with no more than 25 Ohms is recommended by the NEC for grounding devices. Wouldn't be a better idea if we decided to ground directly the metal case of the electronic equipment by using earth conductors and ground rods, instead of having an electronic device delivering the current path for the lightning?

Whats is the advantage of using grounding devices?

 

[bphgravity]

I've heard that 90% of Lightning damages can be eliminated if the electrical system is properly grounded.

Not true. The grounding of your electrical service MAY result in the mitigation of damage due to surging events such as lightning, but the only way to provide REAL lightning protection is to install a conventional lightning protection system per the NFPA 780.

However, a current path with no more than 25 Ohms is recommended by the NEC for grounding devices.

This too is not true. The 25-ohm value found in section 250.56 only applies to the resistance of single rod, pipe, and plate electrodes. Otherwise, the 25-ohm value has NO significance what-so-ever.

Wouldn't be a better idea if we decided to ground directly the metal case of the electronic equipment by using earth conductors and ground rods, instead of having an electronic device delivering the current path for the lightning?

Whats is the advantage of using grounding devices?

Not sure what you are asking here, but all the grounding in the world is not going to protect your premise wiring devices and equipment. Protection of these items can only be done using TVSS and other surge protection devices at the service and at each component.

 

[charlie b]

I think you have a fundamental (and very common) misconception about the purpose of connecting ground wires to the cases of equipment. Planet Earth is not a player in this game. There is no reason to ever run a wire from a metal case to dirt. The case is connected to an ?Equipment Grounding Conductor,? the other end of which is attached to the Ground Bus at the main panel, which in turn is bonded to the Neutral Bus. The fact that this point is also connected to a wire (the ?Grounding Electrode Conductor?) that in turn is attached to the ground rod, means nothing to the equipment. The purpose of the EGC is to carry fault current back to the source, in the event a hot wire comes into contact with the case, with the result that the breaker will trip on overcurrent. In other words, the function of the EGC is to facilitate the termination of a fault event. The fault current will not flow through the GEC and into the ground rod. Rather, it flows directly to the source.