Basic Definitions

Ambient Temperature - The temperature of the air, water, or surrounding earth. Conductor capacity is corrected for changes in ambient temperature including temperatures below 86°F. The cooling effect can increase the current carrying capacity of the conductor. 

Bonding Jumper - A bare or insulated conductor used to ensure the required electrical conductivity between metal parts required to be electrically connected. Frequently used from a bonding bushing to the service equipment enclosure to provide a path around concentric knockouts in an enclosure wall: also used to bond one raceway to another.

Demand Factor - For an electrical system or feeder circuit, this is a ratio of the amount of connected load (in kva or amperes) that will be operating at the same time to the total amount of connected load on the circuit. An 80% demand factor, for instance, indicates that only 80% of the connected load on a circuit will ever be operating at the same time. Conductor capacity can be based on that amount of load.

Megger - A test instrument for measuring the insulation resistance of conductors and other electrical equipment; specifically, a mega ohm (million ohms) meter; this is a registered trade mark of the James Biddle Co.