Wiring and Grounding - Internal

In a number of our discussions we've mentioned how wiring errors contributed to the creation of a disturbance. Improper wiring may be either the cause or the effect of power problems.

Anytime sensitive loads are used, great care should be taken to ensure the wiring and the grounding are appropriate. Every aspect of the power system should meet, or exceed, the National Electrical Code requirements. It is important to realize that the Code is not concerned with power quality, rather its concern is with safety. If the Code says to use a #8 neutral wire, it's OK to use a #6 in order to reduce the threat of overloaded neutrals.

The impact of improper grounding cannot be understated. Combinations of devices such as POS terminals, computers, and transaction verification systems means that poor grounding can significantly affect their operation and their reliability.

Should a local area networks (LANs) be in place, grounding is even more important. In computers, the internal digital reference is usually tied directly to the input power ground. Therefore, the digital reference of PC #1 on the LAN is the outlet it is plugged in to. The same applies to PC #2. If a voltage difference exists between these two ground points, then current will flow through the data cable connecting the two PCs. This can disrupt and even damage the I/O ports of the PCs.

If wiring is found that violates the Code, it should be fixed immediately. Oftentimes, bringing the electrical system up to Code resolves many power quality problems.

If poor grounding is a concern, the use of isolated ground receptacles, isolated ground busses in the panel, and isolated ground conductors will alleviate most problems.

If an isolated ground conductor is used, it should be run in the same raceway as the power conductors, and terminated at the neutral-to-ground bond of the power source. This source is the transformer or service entrance directly feeding the loads.

Using ground rods for grounding sensitive electronic devices inside the building is not recommended.