Whether you are new to the industry or are well seasoned and want to review some of the basic information that you learned in the past, these courses and lessons will clearly outline what you are looking for. “Power Systems Electric” is On-Line training that bridges the gaps between textbook theories and practical power systems experience. As a retired electrical engineer who has gone through the experience of developing a career in electrical power systems, I know how frustrating it can be to try and find the answers, so I put together these courses that I feel would have been a major help to me in my development. I have also taken suggestions from students of what they would like to see in addition to these courses which I have given live in person.

Basic Electrical Learning

For those new to the industry, there is a beginner’s group of courses that cover the “Fundamentals of Electricity ” including DC and AC Circuit Analysis. These lessons examine such basics as Ohm’s Law, Series, and Parallel Circuits. The first, and perhaps most important, relationship between current, voltage, and impedance, “Ohm’s Law”, and its relevance to Series and Parallel Circuits. Subsequently, this will lead to the development of Kirchhoff’s Laws as they help to further analyze Network Analysis & Metering Circuits.

Conductors and Insulators are investigated along with their connected components, Capacitors, Inductors, and how they are influenced by Electromagnetism.

Alternating Current (AC – an electric current that periodically reverses direction) is the form in which electric power is delivered to businesses and residences, and it is the form of electrical energy that consumers typically use when they plug kitchen appliances, televisions, fans, and electric lamps into a wall socket.

The abbreviations AC and DC are often used to mean simply alternating and direct, as they are applied to current or voltage.

These AC courses deal specifically with sinusoidal waveforms and will provide the student with the basic understanding of working with circuits involving Alternating Current, which includes sinusoidal waveforms, vectors & phasors, reactance & impedance of R,L,C circuits, as they relate to the basic laws and theorems of electricity. This includes working with AC Power, Power Factor, Resonance, Complex Numbers, Reactance, and Impedance

Advanced Electrical Learning

These Courses involve subjects such as “Short Circuit Analysis for HV Three-Phase Systems ” which introduces the student to the basic concepts of fault studies on a high voltage three-phase system. System modeling is then used in order to aid in this process, with the ability to move between asymmetrical and symmetrical systems. With hey Searle and extensive study of “Per Phase” & “Per Unit” methodologies system faults are analyzed with the use of symmetrical components.

“A Per-Unit System ” is the expression of system quantities as fractions of a defined base unit quantity. Calculations are simplified because quantities expressed as per unit do not change when they are referred from one side of a transformer to the other.

In these courses, you will learn exactly what Per Unit Analysis is, the main advantages of using it, how manufacturers of equipment use and rate their products, and the technique of converting to and from the Per Unit system.

Several examples of working with Per Unit are demonstrated in this crisp clear presentation. When you finish you will have a though understanding of this subject.

It is important for all power engineers and technicians to be familiar with the concept of Per Unit as it is being used and referred to every day in power flow, short circuit evaluation, and motor starting studies.

The method of “Symmetrical Components ” is used to simplify asymmetrical three-phase voltages and current analysis by converting the unbalanced system into two sets of balanced phasors and a set of single-phase phasors, or symmetrical components. These sets of phasors are called the positive, negative, and zero sequence components.

An understanding of this method is essential for the understanding of fault analysis and modern-day protection schemes. These courses will provide you with the knowledge to comprehend the concept and how it is applied.

Supplemental Electrical Lessons

In all power electrical analyses, the student will encounter special Trigonometric and Mathematical identities and equations. This site contains special supplemental lessons that zero in on those identities and equations. For example, there are lessons that take you from the “Fundamentals of Trigonometry ” to the more sophisticated requirements in electrical engineering. As you work and study in electrical engineering you are going to run into proofs and equations that are based on trigonometry. A good example of this is when studying AC current, voltage, and impedance calculations, phasors or vectors are used and combined mathematically. Further adventures into complex power will also require a knowledge of trig functions and identities. As a student of this course, you will be introduced to these or at least re-introduced to these that may have been long since forgotten.
In mathematics, “The Derivative of a Function ” of a real variable measures the sensitivity to change of the function value (output value) with respect to a change in its argument (input value). Derivatives are a fundamental tool of calculus. For example, the derivative of the position of a moving object with respect to time is the object’s velocity: this measures how quickly the position of the object changes when time advances.

Specialized Electrical Lessons

Specialized lessons include the “Protection & Control(P & C)” principles of high voltage stations. HV Bus Differential Protection is studied along with restrictions due to CT saturation & mismatch and its solution, “Restraint Differential Protection”.

High Voltage Circuit Breakers are examined as to the various Types (Oil, Vacuum, Air Blast, SF6), their Controls as well as the introduction of potential transformers & current transformers, and their use in conjunction with the relevant instruments such as ammeters, voltmeters, watt meters, and energy meters.

Other lessons include the study of “Transformers ” including core construction along with losses, cooling, and mitigation techniques. Three-phase transformer configurations are studied along with harmonic distortion, CT saturation, and on-load tap-changer problems and how these problems are dealt with. Over-current and restraint differential transformer protection is developed along with a look at some examples of ” Old School relays” as well as modern IDE (intelligent Electrical Devices) relays.

Transformer Connections: (Y – Y; Delta – Delta; Y – Delta; Delta – Y & Y – Zag Zig) are examined along with Transformer Clock System Vector Nomenclature.

Lastly, there is a special section dedicated to “Single and Three-Phase Metering “, including old analog and new digital kilowatt-hour meters.

Conclusion

Regardless of whether or not you are new to the industrial power system, you’ll find what you’re looking for on this site in the way of training. In order to review or select any of these courses, left-click on any of the blue highlighted hyperlinked words of this posting or on “14 Courses Available” from the top menu of the landing page. All of the courses have a free introduction

As a bonus and in the way of a thank you, for your interest in PSPT’s WEB (and Blog) page, I’m making available my 50-page “Electrical Power” crib sheets. These were prepared for use with my courses that are available on this site. There is one section associated with each course and is extremely valuable while viewing the course, as well as a recall of the pertinent formulas and information after the fact. The contained information is also useful during any technical career as a quick reference from time to time. Simply click here or on the picture to the right to be taken to where you can download this item.

October 26, 2022

Blog #12 -Household Electrical Wiring - Boxes & Connections

October 26, 2022/ Graham VanBrunt

This blog is a continuation of low-voltage electrical wiring found in residential homes. Most of it applies to any installation that uses a 120/240 AC volt supply. We will begin this blog by going over the different types of electrical boxes.

Electrical boxes are critical components of your home's electrical system. But for many do it yourselfer's, the wide variety of boxes is bewildering. There are plastic and metal boxes; "new work" and "old work" boxes; round, square, and octagonal boxes; and boxes with load ratings for ceiling fans and heavy light fixtures.

All of the most commonly used boxes for home wiring projects, are available at home centers and large hardware stores, and it's important to know the differences in order to buy the correct boxes. There are a number of options to consider: material, shape, size etc.

Most electrical boxes are either metal or plastic. Metal boxes are generally made of steel, while plastic boxes are either PVC or fiberglass. Weatherproof metal boxes for outdoor use are generally made of aluminum.

If you are using metal conduit to run wiring to the electrical box, then a metal box is required, both to anchor the conduit, and because the conduit and metal box system itself may be used to ground the system. If you are using non-metallic cable, such as Type NM (non-metallic sheathed cable), then you can use either plastic boxes or metal boxes, as long as the cable is secured to the box with an appropriate cable clamp.

Modern wiring systems with NM cable usually include a ground wire inside the cable, so the box is not part of the grounding system (however, metal boxes, must be connected to the system ground, usually with a short length of wire called a pigtail).

Like standard rectangular boxes, some are used to hold household switches and electrical outlets, as well some are oversized so that two, three, or four devices can be mounted side-by-side. Like other boxes, these come in a variety of "new work" and "old work" designs, some with built-in cable clamps.

The same effect can be created by using standard rectangular boxes with a "gangable" design that allows the sides to be removed so the boxes can be joined together to form larger boxes.

Round pan or "pancake" boxes typically are only 1/2 inch or 3/4 inch deep. They are used most commonly for ceiling or wall mounted light fixtures that weigh no more than 50 pounds. Some types of specially rated metal pan boxes may be used for mounting ceiling fans, but not all pan boxes may be used for this purpose.

It's important that the fixture wires can be properly connected and fitted within the round pan box. These are shallow electrical boxes with only enough space for fitting two or three electrical connections. If there are more wire connections to be made, you will probably need a full-sized octagon or round electrical box with more volume. The number of wires in the box should never exceed its safe fill capacity.

Square boxes come in standard depths of 1 & 1/4 to 2 & 1/8 inches, but their square corners give them additional interior space, providing maximum volume for multiple conductors and connectors. For this reason, 4-inch square boxes often are used to run multiple conductors in two or more directions. They are also commonly used as junction boxes, and can also be installed in ceilings or walls for supporting lighting fixtures or for housing switches or receptacles when matched with the proper cover plates.

This is also known as a junction box. It is not a special type of box, but rather a term used to describe any standard electrical box used to enclose wire splices. The standard box used for junctions is a 4-inch square box, which offers plenty of space for making wire connections with multiple wires or cables, but other types of boxes can be also used for this application.

Junction boxes must be installed where they are always accessible Never install a junction box in a concealed wall, or ceiling space, where the box cannot be accessed in the future. Junction boxes also must be covered with solid covers with no holes.

Electrical box covers come in a wide variety of sizes and shapes, to match different types of boxes. A cover is used to enclose the front of the box and is required by code; it is unsafe, and usually illegal, to leave an electrical box uncovered.

Solid, or "blank," covers have no holes and typically are used with junction boxes, or for enclosing unused boxes. Covers for 4-inch square boxes may have special cutouts or knockouts to accommodate switches or receptacles (outlets). These typically include a raised center area that extends the box so the opening for the switch or outlet will be flush with the exposed surface of the drywall or other wall or ceiling finish.

Weatherproof, outdoor boxes, are sealed enclosures, designed for mounting to the surface of exterior walls, roof overhangs, decks, and other structures. They are used for installing outdoor receptacles (outlets) and light fixtures. Outdoor boxes must have an outdoor cover, or fixture rated for damp or wet locations, depending on the application.

Plastic outdoor boxes are usually made from high-impact PVC, while metal outdoor boxes are typically made from aluminum rather than steel.

Box extenders, or extension rings, come in a variety of sizes and shapes to match standard electrical boxes. They are shaped like boxes but have no back. They are designed to be installed onto the front of standard electrical boxes to increase the box capacity or to bring the box flush with the drywall or other surface material.

The National Electrical Code, (NEC), dictates that no wiring splices are allowed outside of an approved enclosure. Any standard outlet, switch box or light fixture box, can serve as an approved enclosure, but where a wiring splice, needs to occur in other locations along the circuit, the approved enclosure is usually a junction box. A junction box is simply a standard electrical box, that is mounted securely to house framing or another structure, containing the connection or (splice) of two or more circuit cables. The cables are secured to the box with cable clamps or conduit connectors if the circuit includes conduit, and the box must have a removable cover, to create a complete enclosure. Junction box covers must remain accessible, they cannot be covered with drywall or other surface material.

A junction box is most often used where an electrical circuit branches off in two or more directions from a location where an outlet or fixture is not practical. It is also a common solution when an electrical circuit is being extended.

Make sure to buy a junction box appropriate for your installation. Outdoor locations, for example, require a weatherproof junction box, with gaskets to prevent moisture intrusion. And, make sure the junction box is large enough for the number of wiring connections you will be making. For example, the smallest 2 by 4 by 1 & 1/2-inch deep box can comfortably splice only two cables (four or five conducting wires), while the largest 4 by 4 by 2 1/8-inch-deep boxes can handle as many as four to six cables (up to 18 individual conducting wires). For easy installation, many DYI’s choose the largest box that is practical for the application.

A "knock out" is a partially stamped opening in electrical enclosures, that allows quick entry of a wire, cable or pipe, via a connector or fitting to the interior. With the right information and technique, you should be able to remove a "knock out" from electrical panels and other electrical enclosures without any problems.

Of course, ensure that the wires you're going to be dealing with are not powered. Switch off all suspect breakers and use a suitable meter or tester to ensure that power is off, reducing the chance of shock or burns.

Locate the knock out stamping sized to fit the desired connector (or fitting). There will likely be several knock outs of different sizes on more than one surface from which to choose. Pick the one that will be easiest to connect the cable or pipe.

Some switch boxes have slots in the knockouts for easy removal using a slotted screwdriver. These switch boxes usually have built-in clamps for securing the cable once entering the knockout location.

When installing cables to junction boxes, separate the circuit wires at the existing splice, and loosen the cables as needed to make room for the new junction box. Anchor the box to the framing (or other support structure) with screws or nails driven through the factory-made holes in the back or side of the box, as applicable.

Install a cable clamp for each cable, as needed. Standard plastic electrical boxes do not have knockouts and contain internal cable clamps. Metal boxes usually have internal clamps;

If the metal box does not have internal clamps, install a locknut-type clamp for each cable. Insert the threaded end of the clamp through a knockout hole, and secure the clamp inside the box with the ring-shaped nut. Tighten the nut with pliers.

Join the wires together with approved wire connectors, following the manufacturer's instructions:

Feed the cables through the clamps and into the box. The cable sheathing, (outer jacket), should extend 1/4 to 1/2 of an inch into the box beyond the clamp and the individual conducting wires should extend about 6 inches into the box. If necessary, trim the wires as needed, and strip 3/4 of an inch of insulation from the end of each wire using wire strippers. Secure the cables by tightening the screws on the clamps, being careful not to overtighten and damage the cables. Plastic boxes usually have spring tabs for clamps and do not require tightening. The ends of the individual wires should be clean, straight, and undamaged, with no more than 3/4 of an inch of exposed wire beyond the insulation. Trim any damaged wires and strip insulation as needed using wire strippers.

Join the bare copper (or green insulated) ground wires together first. If the box is metal, add a pigtail, a 6 inch length of the same type of ground wire, to the ground wire connection, then connect the loose end of the pigtail to the ground screw on the box. Special green wire nut connectors are generally used to join the grounding wires together. however; the same type of wire connector can be used for all the connections.

Join the white, (neutral) wires together, then join the black (hot) wires together, using a wire nut or other approved connector for each wire pair. If there are red wires, join them together as well. Confirm that all wires are secure by gently tugging on each wire.

Carefully fold the wires into the box and install the box cover, securing it with two screws. The code requires that the cover must be solid and "blank" without holes. Restore power to the circuit by switching on the circuit breaker.

In your home's wiring system, the power is normally carried by the hot wires to the load, while the neutral wires, provide a return path to the source after the load. Both sets of wires enter your home through the utility's main service wires, running through your electrical service panel, and run side-by-side through every circuit in your home.

Should some breakdown of the pathway occur, the power may instead flow through other materials, such as metal framing, metal pipes, or conducting but flammable materials in your home. This is what may happen in a short circuit situation, where most electrical fires and shocks originate. A short circuit is when electricity strays outside the wires that it is supposed to flow through. In other words, when it takes a shorter path.

To prevent this danger, your home's electrical system includes a backup plan, a system of grounding wires that runs parallel to the hot and neutral wires. It provides an alternate pathway for electrical current to follow should there be a breakdown in the system of hot and neutral wires that normally carry the power. If a wire connection becomes loose, for example, or a rodent gnaws through a wire, the grounding system channels the stray current back to ground by this alternate pathway before it can cause a fire or shock.

The grounding pathway is generally formed by a system of bare copper wires, that connect to every device and every metal electrical box in your home. In standard sheathed NM cable, this bare copper wire is included along with the insulated conducting wires inside the cable. The bare copper grounding wires terminate in a grounding bar in your main service panel and that grounding bar is in turn connected to a grounding rod driven deep into the earth outside your home. This grounding system provides a path of least resistance for electricity to follow back to ground should a break in the wiring system allow electricity to "leak" out of the preferred system of black and white circuit wires.

In some instances, the code requires electrical cables to have mechanical protection, in which case rigid conduit or flexible metal clad cable must be used, Metal clad (MC) cable is easier to work with, than rigid conduit and offers protection from fire, vibration, gnawing pests and physical harm in general.

Metal clad cable comes in several varieties, but the type you’ll find most commonly has 3 insulated wires (two circuit conductors and a green or bare equipment grounding conductor), protected by a flexible armor, usually made from aluminum. MC cable is identified by the gauge of the wire, not the diameter of the armor. The most common sizes are 14 gauge, 12 gauge, and 10 gauge.

MC Cable is used only with Metal Boxes! Plastic or fiberglass electrical boxes aren’t designed to be used with MC cables. Even if you’re able to rig up a connection to a plastic box, it will fail the electrical inspection. Make sure the metal box has knockout holes located where you need them and don’t rely on the spurs on the bracket to hold the box in place, add a couple of screws as well.

Flexible metal conduit, (FMC), is commonly called “Greenfield” or just “Flex”. The main difference between MC cable and FMC, is that FMC doesn’t have the insulated wires pre-installed. You have to pull them through after the fact. This requires more work, but gives you the option of pulling and protecting, more than one circuit in the same conduit. It also allows you to add wires in the future, something you can’t do with MC cable. FMC is identified by its diameter; the most common sizes are 1/2 inch & 3/4 inches. and 1-inch.

Liquid-tight flexible conduit is installed wherever the wiring will be subjected to wet conditions. Liquid-tight flexible conduit is water resistant and is available without the wires installed and in short lengths or (whips) that come prewired. There are two common types. liquid-tight flexible metal conduit and liquid-tight flexible nonmetallic conduit.

Liquid-tight flexible conduit applications include HVAC Equipment, machine tools, marine equipment, motors and controls, printing equipment, pumps, refrigeration equipment, transformer connections, and outdoor lighting.

If you have, just one or two cuts to make and don’t want to invest in a cutting tool, bend the MC cable sharply until the armor pops open and then use that opening to start the cut with side cutter pliers. You only need to nip through one section in the armor. This method will leave a jagged edge that will need to be trimmed after the armor is separated and the cut ends of the MC cable will be sharp, so be sure to wear gloves.

If you have a lot of cuts to make. A Rotary Cutter Works Best for MC Cable. Cutting the armor without damaging the wires is probably the trickiest part of working with MC cable. The best method is to use an armored cable rotary cutter. This tool uses a small cutting wheel powered by a hand crank and will cut only through the armor, leaving the wires undamaged every time.

You can attach a connector to MC cable, then join it to the box, but it’s easier to mount the connector on the box before feeding the wires through. Connectors like those shown above are popular with electricians because the one screw secures both the connector to the box and the MC cable to the connector. There should be a minimum of 6-8-in. of exposed wire inside the box.

In order to protect the conductors from damage caused by the sharp ends of the cable, plastic anti-short bushings are used. Even if the connector you’re using has its own bushing, make sure to add a bushing like the one shown here. It’s a cheap and easy way to achieve an extra level of protection. Some manufacturers supply a bag of anti-short bushings when you buy the cable or you can buy a pack for a couple of dollars.

After cutting when removing a section of armor to expose the wires, twist the short end of the cable counterclockwise as you pull the cable apart. If it feels like it’s taking too much pressure to separate, double-check that the cut went all the way through the armor. Don’t pull too hard or the armor could separate farther down the line. That’s a problem because damaged armor shouldn’t be installed and may have to start over.

Make sure the box is grounded. Whether it’s the first box in a line or the only one on an entire circuit, every metal box needs to be grounded. Grounding a box is as simple as connecting the incoming and outgoing ground wires to a pigtail, and then connecting the pigtail to the box with a grounding screw.

Secure the MC Cable, with clamps such as these single-hole straps, that make it easy to provide sturdy support. Avoid connecting them with nails or you’ll risk smashing and damaging the cable with a hammer. Install a strap within 12 inches of each box. All subsequent straps need to be within 6 feet of each other. When you’re routing cables, be sure to avoid sharp bends that could damage the cable sheath or the conductors.

Any home handyman who has undertaken any electrical work has used wire nuts. A wire nut is a device that aids in the connection of a group of electrical wires. It not only holds the joint secure, but provides insulation for the mechanical wire joint.

It should be noted that "wire nuts”, is a trademark of “Ideal Industries”, but like Kleenex, it has become the primary identification for the product. Many manufacturer's make similar products, under their own trade names and trademarks.

Making tight electrical connections is critical to a safe wiring job. If wires come loose, you could get arcing and overheating, which could lead to a fire. It also means that the circuit may be interrupted, that is, it will not work. But thanks to reliable connectors and terminals, it's fairly easy to make safe, strong connections. Still, there are a few things you have to watch out for. Picking the right connector for the job, and preparing the wires are important for the best connection. With careful attention to detail, you can rest easy, knowing your wiring job is as safe as you could possibly make it.

When preparing wires to be connected, cut off nicked, bent or twisted ends. Wires that are bent twisted or nicked, are weaker and won't nest together as easily in the connector. Before you reconnect or rejoin several wires with a connector, cut off the old bare ends. Strip the insulation to expose the clean, straight wires. Extend the ends of all stranded wires about 1/8 of an inch beyond the solid wires. Then install the wire nut connector as usual. If you hold the ends of solid and stranded wire even with each other, while you screw on the wire nut connector, the stranded wire will often wrap loosely around the solid wires, resulting in a loose connection. This is especially likely when you're joining multiple solid wires, to one stranded wire.

When installing the Wire Connector, arrange the wires parallel to each other with their ends aligned. Place the wire nut connector over all of the wires. Keep your eye on the wire ends until the connector covers them to make sure none slips out of position. Twist the connector until the insulated wires outside the connector begin to twist. Tug on each wire to make sure they are secure.

Wire nut connectors come in many sizes, and every wire nut connector is made to join a certain minimum and maximum volume of wires: The larger the wire gauge, the fewer it can hold. Check the list on the wire nut connector packaging to make sure your combination of wires is safe. Even though the connectors appear to be colour-coded, you can't rely on this. You have to check the label on the package or go to the manufacturer's website to find out. Keep a range of small to large wire nut connectors and their packaging on hand, so you won't be tempted to make do with the wrong size.

New to the electrical industry, is the Wago Lever-Nuts (221-Series). Which is providing a better alternative to the wire nut. With the 221 series Compact Splicing Connector for all conductor types, Wagner provides electricians with a fast, easy and safe way to terminate, solid, stranded, and find stranded conductors without tools.

The 221 series portfolio includes 3, 4 and 5 wire connectors in 12 and 10 AWG maximum versions. The original model connectors accommodate all conductor types, ranging from 24 to 12 AWG. The 10 AWG model connects all conductor types ranging from 20 to 10 AWG. This flexibility permits a wide range of applications, especially when conductors of different types and sizes are used together.

Wiring is simple. First strip, the conductor, according to the strip length guide printed on the side of the connector housing.

Open the clamping unit via the easy to use lever insert conductor, then simply lower the lever to close the clamp.

The transparent housing permits visual inspection of the conductor position. It clearly shows that the conductors have been stripped and inserted properly. A gas-tight contact point provides a durable and secure connection between the conductor and the current bar.

Furthermore, two easily accessible test ports, one in the conductor entry direction and one opposite of this simplify testing even when installed.

The 221 series has an operating temperature rating of 105 degrees Celsius, making it ideal for a variety of industrial environments. These connectors have been tested to meet the safety standards of Canada and the United States by Underwriters Laboratories listed according to UL486c.

With a wire-stripping tool, stripping the ends of the wires becomes an easy and quick task. Check the label on the connector package for the length of the bare wire to expose. For all but the smallest and largest connectors, this is usually about 1/2 to 5/8 inches.