BEST OF CODE TIME 3: Feeder & Service Entrance Conductor, Mechanical Execution of Work & Panelboards

There are a lot of sometimes confusing terms that we must learn as electricians. Especially considering that there are many different terms used to describe the same thing! In the latest episode of Electrician U, Dustin explains Feeder & Service Entrance Conductors, Mechanical Execution of Work, and Panelboards.

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Article 100 of the NEC defines Feeders as “all circuit conductors between the service equipment, the source of a separately derived system, or other power supply source and the final branch circuit overcurrent device”. In essence, a set of wires leaving the service and “feeding” another panel or distribution point. There are two definitions for Service Entrance Conductors in the NEC (one for overhead and one for underground). An overhead service entrance conductor is defined as “The service conductors between the terminals of the service equipment and a point usually outside the building, clear of building walls, where joined by tap or splice to the service drop or overhead service conductors”. An underground service entrance conductor is defined as “The service conductors between the terminals of the service equipment and the point of connection to the service lateral or underground service conductors”. So, the term feeder really describes a set of conductors AFTER the service feeding something while service entrance conductors describe the conductors BRINGING IN the service to our building.
When it comes to HOW we install our electrical work, we must install it correctly and properly not just a rag tag installation! Article 110.12 of the NEC tells us “Electrical equipment shall be installed in a neat and workmanlike manner”. That in itself tells us that we must install our work in a neat systematic order. The code goes on to tell us that we must close up any unused openings (we don’t want someone sticking something into a panel that would cause an arc flash), that the parts of the equipment cannot be damaged or contaminated with anything they aren’t supposed to have on them and that cables & conductors installed exposed on a surface of ceilings and walls shall be supported in a fashion that will not damage the cables.
Article 408, Part 3, governs the installation of Panelboards. Article 408.30 specifically tells us that the panelboard shall be protected by an overcurrent protective device that does not have a rating greater than the panel itself. So, you cannot protect a 225a panel with a 400a breaker! The panel could fail before the breaker trips. The NEC also states that the overcurrent protective device shall be located within or at any point on the supply side of the panelboard. That is why some of the panels we encounter are Main Lug Only and some are Main Circuit Breaker. As long as the panel is being protected by an overcurrent device on the Line Side of the panel, then the breaker doesn’t necessarily need to be IN the panel. However, Article 225 Part 2 (buildings or other structures supplied by a feeder or branch circuit) has some additional items to consider. 225.31 says that a building or structure have a disconnecting means for it. So, if you have a separate building it needs to have a means of disconnect for that building. That COULD be a panel or a disconnect. Many times, it is easier to place a panel on the exterior of the separate building and therefore provides a means of disconnecting power to that building.
We hope this has been helpful in understanding some of the terms and codes in the NEC. Is there a topic you would like to see discussed? Leave a comment in the comment section and let us know! Please continue to follow Dustin and Electrician U as we are constantly adding new content to help our followers be the best they can be!