Randy Hunter works for Cooper Bussmann. He holds twelve inspections certifications from IAEI, ICC and IAPMO. Randy is IAEI Southwestern Section secretary, Southern Nevada IAEI Chapter president, a former principal member of CMP-6. Randy current serves on CMP-17, is a voting member of UL 1563, Electric Spas, Equipment Assemblies, and Associated Equipment, and has served on several Southern Nevada local code committees and electrical licensing committees. He has been a master electrician since 1988, and prior to that he designed and built computed numerically controlled (CNC) machine tools.
Article 310, Conductors for General Wiring
We have finally reached the portion of the code that deals with conductors. Conductors are used on every electrical installation, so naturally we have a variety of installation conditions and a wide range of applications. Again, keeping to the scope of work for combination inspections, I will discuss only the most common installations that may be experienced by a fellow combination inspector.
Article 300 Continued: Electrical Inspections for the Combination Inspector
In the last issue we ended with the requirements for underground installations in 300.5. We’ll pick up where we left off with 300.6, Protection against Corrosion and Deterioration. The basic requirement is that equipment must be suitable for the environment in which it is installed.
Chapter 3, Article 300, Part 1 — Electrical Inspections for the Combination Inspector
Well we’ve made it to chapter three of the National Electrical Code. I like to refer to this area of the code as the "nuts and bolts” of an electrical installation. Chapter 3 is entitled Wiring Methods and Materials, and it covers much of the mechanical portion of the code. This includes what materials we use, how to install them and where. For those preparing for a certification test, this is usually one of the key portions of the test for both open and closed book questions. In Article 300, almost every section is one you need to know to do both good quality installations or to perform thorough inspections of basic electrical systems.
Article 250 — Grounding and Bonding
Article 250 is the largest article in the National Electrical Code. It is often the most dreaded by those new to the code, and sometimes even by those who have dealt with the code for years. Some of the terminology is confusing and conceptually difficult to follow. In keeping with the Combination Inspector emphasis of this series of articles, we will cover those items which I have previously taught to inspectors who weren’t electrical by trade. In doing so, we will not cover every section of Article 250, but concentrate on those that are used most commonly by multi-trade inspectors.
Article 240, Part 2 — Overcurrent Protection
In Part One of Article 240, we left off with a basic review of circuit protection. Now that we have an understanding of how it operates, let’s get back to Part II of Article 240 which starts at 240.21 Location in Circuit. Here we find a very simple statement which requires the overcurrent protection to be located at the point where ungrounded conductors receive their supply. As simple as this is, we naturally have exceptions which will allow taps to be made under certain conditions. For this section, a tap is a conductor which is connected to a system; however, it is not sized to handle the ampacity of the upstream overcurrent protective device. We will cover the limited allowable conditions. But first, the last sentence of 240.21 needs to be emphasized; it explains that under the tap allowances in 240.21(A) through (H), you may not have an additional tap made to any of these allowed taps, or as I used to tell inspectors, "You can’t tap a tap.”
Article 240, Part 1 — Overcurrent Protection
Overcurrent protection is a subject on which we could write volumes; however, our objective here is to cover the basics in order to provide the information needed for the combination inspector. This is actually a fun portion of training, as we usually take apart devices and explore how they operate. Check out the included photos that illustrate some of the details that we usually look at in training classes, and don’t be hesitant about disassembling equipment (that you don’t plan to install later!) to see what is inside.
Article 230, Services
Article 230 is in some ways the genesis of the electrical system, meaning that it is very often the starting point of the electrical installation for a facility. Therefore, this is where I would usually commence my inspection process. As a rule of thumb, if the service is installed in a good workmanlike manner, the rest of the installation would also look good. However, if the service is a mess, you can generally assume that you are in for a long inspection and several items to note on your inspection record.
Article 225 — Outside Brach Circuits and Feeders
Outside branch circuits and feeders — what is so special about these circuits that we require a completely separate article when they are located outside? What makes them different from inside branch circuits and feeders? The scope of this article covers the requirements for branch circuits and feeders running on or between buildings, structure, or poles on the premises, which would also include the wiring for the supply of utilization equipment that is located on or attached to the outside of buildings, structures or poles.
Article 220, Continuation
Starting with Part III of Article 220, which is titled Feeder and Service Load Calculation, we will finally start with the actual math work. First, we will discuss demand factors as referenced in 220.42, and listed in Table 220.42. These demand factors take into consideration that in buildings we don’t normally have every electrical device operating at the same time. For instance, in a residence you will see in the table that the first 3000 VA is taken at 100%, then from there on we step down to a factor of 35% up to 120,000 VA, then down to 25% beyond that. If we refer to Table 220.12, we find that in dwelling units we use 3 VA per square foot.
Article 220 — Branch-Circuit, Feeder, and Service Calculations
Article 220 is a cornerstone of the National Electrical Code which gives us the information we need to properly size the circuits which will provide power to each part of our electrical system. Fundamentally, it is the section of the code which requires the most detail, and during certification testing it is usually one of the most dreaded. Good organization and some basic math skills are required to properly perform the calculations found in Article 220.
Article 215 — Feeders
Since Article 215 is simply titled "Feeders,” let’s start by answering the question "What is a feeder?” If we check Article 100, we find that the definition of a feeder is: "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.” With that definition in mind, let’s take a practical look at what that means in a building. In most larger projects we have a main service, which is the point at which the serving utility provides power.
Article 210, continued
Part II of Article 210 deals with Branch-Circuit Ratings, starting with conductor sizing. These are some pretty basic rules so we will just cover the highlights here. First, the conductors have to be sized for the loads they will serve. There are two basic types of loads, which are categorized by the length of time they will be used. Non-continuous loads are those loads that are turned off and on frequently. Continuous loads are loads that run for three hours or more without interruption
Article 210, Branch Circuits — Part 2
In this article we will continue where we left off discussing branch circuit requirements, picking up with 210.8, Ground Fault Circuit-Interrupter Protection for Personnel. First, we must take notice that this is for personnel protection only. There are other types of ground-fault protection which will be covered later in theNEC. Ground-fault circuit-interrupter (GFCI) protection was first introduced in the 1968 version of the NEC for swimming pool lights. Since then, the Code has continued to embrace and expand the requirements for GFCI protection.
Electrical Inspections for the Combo Inspector, Part 7 — Article 210, Branch Circuits
This installment picks up with the beginning of Article 210, which covers branch circuits. As we recall from Article 100, abranch circuitis that portion of the wiring which connects the final overcurrent device to the utilization equipment. Branch circuit rules for motors are covered in Article 430 due to the special and unique requirements related to motors. If we have combination loads that include motors and other utilization equipment, then both Articles 210 and 430 will apply.
Electrical Inspections for the Combo Inspector, Part 6. Article 200, Use and Identification of Grounded Conductors
This is the part of the NEC where new code students often start to become confused. It is essential to clearly explain the difference between grounded and grounding, and then find a way to etch this into the student’s mind so he or she will not confuse or misuse the terms. Therefore, we will go into detail to clearly identify the difference between the two terms.
Article 110, Requirements for Electrical Installations
In the last issue we discussed the NEC requirements up through 110.14, Electrical Connections, so we will start with 110.15, the requirement for identifying the high leg. Now you’re probably asking, what is ahigh leg? To answer that, we have to review some of the basics related to voltages and transformer windings and connections. We have two basic transformer configurations, wye and delta.
Article 110 – Requirements for Electrical Installations
Welcome back as we continue to discuss the 2011 National Electrical Code for the combination inspector. We are finally getting into the body of the code with Article 110, which covers the basic requirements for electrical installations and applies throughout the code, unless specifically overruled in any article in chapters 5 through 8. Some of the items covered in this article are the requirements for examination, installation and use, terminations, and access to and spaces about electrical equipment. Over the years I’ve often had inspectors and electricians ask me where in the code it states some basic rule, and more often than not it is a requirement in Article 110.
Electrical Code for the Combination Inspector, Part 3
Last issue we made it through the "g” definitions in Article 100. In this article, we will finish reviewing selected definitions. Our first definition isin sight from(within sight from, within sight). These variations of phrase are used in various parts of the code, but would likely engender many arguments over meaning if the Code did not include a clear definition.
Electrical Code for the Combination Inspector, Part II
Article 90 is rarely given consideration when someone references the National Electrical Code (NEC). However, this is where we find the purpose statement for this code, and it shapes the entire application and enforcement of the requirements in the NEC. According to Section 90.1, the purpose of the NEC is for "…practical safeguarding of persons and property from hazards arising from the use of electricity.” Section 90.1 makes it clear that the requirements in the NEC will result in an essentially safe electrical system, but that it may not be efficient, convenient or even adequate for good service. The code explicitly states that the NEC is not a design manual and is not intended for untrained persons. By implication, this means that the NEC is intended primarily for electricians, electrical engineers and electrical inspectors, since these are the professions that are trained to understand and apply the requirements within this code.
Electrical Code for the Combination Inspector, Part I
The combination inspector is an integral part of the inspection process in many inspection agencies across the country, including the entity for which I have worked for close to two decades. I was hired as an electrical inspector; however, on my first day (within the first hour) one of the supervisors placed a stack of code books in front of me, including the UBC, UMC, UPC and the only one I recognized — the NEC. The supervisor who placed the books in front of me then announced I was one of their new "combination inspectors.” Thus began a crash course of training in subjects to which I had never before been exposed. I thought I had it dialed in: I was a master electrician, knew the NEC pretty well and had finally got a job where I could utilize the knowledge I had, but that changed the first day.
Rooftop Wiring Methods and Temperature Correction
Since at least 1940, the National Electrical Code has contained a requirement for ampacity correction of installations subject to high temperature conditions. In the 2005 NEC, a new fine print note was added to inform code users that if conductors in conduit were exposed to direct sunlight in close proximity to rooftops, they might experience an additional 30°C temperature rise above ambient (NEC-2005, 310.10 FPN 2).