The Isolated Ground (IG) is a type of equipment ground that, in theory, reduces interference experienced by electronics and instrumentation from radio frequency (RF) noise, by connecting that equipment directly to the grounding terminal of the service equipment, without ever making contact with another metal component or grounded surface, that could potentially be serving as an antenna for airborne RF noise.
The NEC has long regulated the required space around electrical equipment installations so that a worker who is going to examine, adjust, service, or maintain equipment that may be energized is not exposed to excessive danger from live (ungrounded) parts. The worker must have enough space available so as not to contact a surface that could effectively make his body a path to ground. In the past, equipment installations above a drop ceiling, such as small transformers, air handlers, VAV’s, and the like, have not been addressed, and the enforcement of Article 110.26 in these spaces has been difficult at best, as the space above a drop ceiling is often very crowded.
Fire Alarm Systems By David Herres Fire alarm systems are at least an order of magnitude more challenging to understand than homeowner-type smoke alarms, even if individual smoke alarms within the home are wired together to work in concert. Fire alarm work must not be taken for granted because if […]
210.52(C) of the 2017 NEC lays out the requirements for kitchen countertops and the receptacles that are required to serve them. The countertop space located directly behind a range, counter-mounted cooking unit (such as a cooktop), or sink may or may not be counted as part of this measurable countertop surface when determining receptacle requirements and receptacle spacing for the countertop. It all depends on the depth of countertop surface behind that component.
Inrush current, also referred to as “locked rotor current,” is the excessive current flow experienced within a motor and its conductors during the first few moments following the energizing (switching on) of the motor. This current draw is sometimes referred to as “locked rotor current” because the current necessary at startup to […]
The NEC underwent some big changes in 2017, including the redefinition of wall space, when it comes to fixed cabinets installed along a wall space. Prior to 2017, a cabinet affixed to a wall in a bedroom, den, library, etc. simply broke that wall space into two separate wall spaces. The measurement along the wall ended once you reached the fixed cabinet, and a new measurement began at the other end of the cabinet – but not anymore!
For our typical AC electrical system, the purpose of the “Main Bonding Jumper” is to connect the equipment grounding conductors (E.G.C.) contained in each branch-circuit and the metal (conductive) service-disconnect enclosure to the Neutral Conductor of the electrical service. The reason for this is: a driven or buried earth ground […]
A “COMBINATION” Arc-Fault Circuit Breaker is NOT equivalent to a “DUAL-FUNCTION” Circuit Breaker. With ever changing electrical Code requirements, a circuit breaker with the ability to provide both Arc-Fault protection as well as Ground Fault (GFCI) protection was long overdue. But beware, the “combination” function that is identified on recently […]
As 2019 begins, the electrical industry is in a state of change with proposed changes to the 2017 NEC codes. As technologies have changed so have the needs to keep electrical safety current to these changes.
Why are you permitted to go no larger than #6 cu for the GEC attached to a driven rod or driven pipe that is being used as a grounding electrode, but you have to use Table 250.66, and all of the proposed size increases in it when using a metal water piping system in the earth, as my grounding electrode conductor?
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