|  | 8.6 | Planning Structured Cabling: Electricity and Grounding
| 8.6.7 | Safety ground connection problems

Large buildings frequently require more than one earth ground. Separate earth grounds for each building are required in multi-building campuses. Unfortunately, the earth ground between buildings is almost never the same. Separate earth grounds for the same building can also vary.

When ground wires in separate locations have slightly different potential (voltage), to the common and hot wires, they can present a serious problem. To understand this, assume that the ground wire for building A has a slightly different potential, to the common and hot wires, than the ground wire for building B. Because of this, the outside cases of computer devices located in building A would have a different voltage (potential) than the outside cases of computer equipment located in building B. If a circuit were established that linked computer devices in building A to those in building B, then electrical current would flow from the negative source to the positive source. Anyone coming into contact with any device on that circuit could receive a nasty shock. In addition, this errant potential voltage would have the ability to severely damage delicate computer memory chips.