Wiring for Power Quality

The table below illustrates some of the new wiring practices recommended to achieve a high level of power quality. Many of the "before" practices are still reflected in building codes today.

Receptacle Outlets per 20 Amp Circuit Before: 13 Recommended: 3 to 6
Neutrals Before: Full size or downsized neutral (on 3-phase systems) Recommended: Use double size neutral (CBEMA) or larger
Before: One neutral shared among equipment (on 1-phase branch) Recommended: Separate neutrals or upsized neutral back to panel
Phase Conductors Before: Standard phase conductor sizing per code Recommended: Use upsized phase conductors to minimize heating for harmonics
Circuits Before: Can shared among many outlets and uses Recommended: Use separate circuits for harmonic-sensitive loads
Grounding Before: Can use metal conduit as grounding conductor Recommended: Use separate insulated wire as grounding conductor
Before: Downsized grounding conductor Recommended: Use full size or over size grounding conductor
Before: (Commercial/Industrial) Must use metal water pipe and a concrete-encased electrode (if available) Recommended: Use a copper ground ring and multiple interconnected ground rods
Before: Use a second ground rod if first is over 25 ohms (no resistance measurement required) Recommended: Use multiple rods or ring and measure to ensure very low resistance to ground
Before: Access floor for equipotential grid in computer mainframe room Recommended: Use copper system for equipotential grid
Before: No lightning or surge protection Recommended: Use lightning and surge protection