A dedicated circuit is intended to power only one device or one “point of use” outlet(s). A dedicated circuit has a continuous conductor run from the circuit breaker to the “point of use” device or outlet(s). This ensures no other equipment or connections can be made between the breaker and the “point of use” device requiring the dedicated circuit. Dedicated circuits are essential for computer-based equipment to ensure the best conditions for reliable operation. Circuits that share other conductors or other loads can incur several issues that negatively impact reliability including circuit overloading, high voltage drop, noise, and neutral to ground disturbances.
An isolated ground (IG) circuit is a dedicated circuit that is typically used to power computer-based equipment. The primary reason for the use of an isolated ground circuit is to provide a noise-free ground reference for the connected equipment by having an equipment ground path that is separate from the other equipment grounding (EG) means within the facility. The EG system and circuits within the facility includes all of the metal conduit, outlet boxes, and metal enclosures that contain the wiring which these must be bonded together and grounded to provide a safe return path in the event of a fault condition and resulting fault currents. Unfortunately for computer equipment, these EG components can carry extraneous noise that may be present within the facility which can negatively impact computer reliability. The IG circuit is typically insulated and separate from these noisy EG components from the computer device “point-of-use” all the way back to the point of earth grounding for the facility. At the earth grounding point of the facility, the IG ground conductor is connected or bonded to ensure the IG circuit is safe in the event of a fault condition and resulting fault currents and it has only one ground reference point which provides a more stable, noise-free environment for the computer device.
Feature image from Engineering Radio.