Note: This may make more since if you read “Electrical Explained” first. This is a continuation of that posting.
Branch Circuitry
The wires from the electrical panel to all the lights, plug receptacles, and other electrical devices are know as the branch circuitry. If the panel represents the trunk of a tree, the wires leading to all the electrical devices are the branch circuit wires. Branch circuit wires come in all shapes and sizes.
In older buildings, knob and tube wire is found. The wire type is named after the porcelain knobs and tubes used to attach this wiring to the building’s framing. The neutral and hot wires are spaced a few inches away from each other and strung throughout the building. This is the first widely used wiring that started phasing out of residential construction around the 1950s.
More modern types of wire used today are nonmetallic-sheathed cable (known as Romex®) and armored cable (known as BX®). Ungrounded versions of this cable became more prevalent in the 1950s. The neutral wire and hot wire are all wrapped together as cable and strung throughout the building. This cable has evolved (such as adding a ground wire) and still is used today. Nonmetallic-sheathed wiring belongs behind walls where folks cannot mechanically damage this vulnerable cable. Armored cable is allowed where it can be seen, like on a wall surface, because it is less vulnerable to mechanical damage. This cable is often seen on the wall surfaces of the garage where cosmetic issues are less important.
Along these branch circuits are junction boxes. Junction boxes are safe places for wire connections to live. Junction boxes can live along the cable where cables are attached to each other or at devices such as plug receptacles, switches, and lights. Junction boxes are made of both metal and plastic. Without junction boxes, arcs or sparks that can occur at these connections and pose a fire hazard. Junction boxes also reduce shock hazards as they make the wire connections less susceptible to mechanical damage and/or human contact.
The above photos are junction boxes. The box flush with the wall is missing a light fixture. The box in the crawlspace is missing a cover. Junction boxes must be covered.
The wires from the electrical panel (where the breakers and fuses live) eventually make it to electrical devices like lights, plug receptacles, and other electrical devices like dryers or attic fans. Understanding how devices work is best achieved by explaining how a plug receptacle works. Think of a plug receptacle as a face. This face has two eyes. Receptacles found in homes built from the 1960s on also have a mouth. Let’s start with the eyes. If you look closely you will notice one eye is smaller than the other. That smaller eye is attached to the hot wire. If you recall, the hot wire is the avenue of power from the utility company into the building. I best remember that the small eye as the hot by considering the monomer, “You’re hot so I’m winking at you!” The larger eye is the neutral wire. The neutral wire is the avenue of power back to the utility company. After your appliance, let’s say the blender, uses power, electrons are returned to the utility company via the neutral wire so they can sell this same power back to you later. Next we will talk about the mouth or the ground. If I ruled the world, I would probably change the name of that wire to “Secondary Neutral”. The ground wire is a second pathway from the receptacle all the way to the main panel where it reconnects to the neutral bar. The electrons then get back to the utility company through the neutral bar. Think of the electrons traveling through the wires as cattle. Good cattle stay in their corals. Naughty cattle, referred to as Mavericks leave their coral and pose a shock hazard. When Maverick electrons leave their hot-in/neutral-out coral they simply want to return to the ranch (utility company). If it can’t get to the utility company through the neutral wire, it will happily take another path. Suppose there is a blender and the wiring inside this device is damaged. The metal exterior case of the blender is charged. All it takes is one to touch the blender and simultaneously touch the kitchen faucet to get shocked. The kitchen faucet is grounded to the plumbing and that plumbing is grounded to the main panel (if the electrician grounded the building correctly). Unfortunately the heart is along that path so unless you have a defibrillator, ground your circuitry with a proper ground wire.
The GFCI (Ground Fault Circuit Interrupter)
One of the biggest safety improvements in electricity was the lightning rod. Ben Franklin showed the world that lighting could be safely diverted into the earth, which is the bases of grounding systems today. I believe that the Ground Fault Circuit Interrupter is a close second in terms of its simplicity and how well it saves lives. The concept is very simple, if electrons going to the blender from the hot side of the receptacle does not pass back through the neutral side of the receptacle, the GFCI shuts the receptacle down. You see, if the electrons are not returning to the neutral, then a person may be in the path of these electrons. In old homes, where ground wires are not available at receptacles, a GFCI provides a cheap way to make the receptacle safe without the expense of grounding. The National Electrical Code NEC allows for non-grounded existing receptacles be GFCI protected without having to establish a ground wire.
GFCI receptacles are typically required on all kitchen counter receptacles, bathroom receptacles, garage receptacles (except those dedicated to major appliances), and exterior outlet. Newer GFCI receptacles have a symbol of a padlock on the face of the receptacles. These GFCI receptacles have been improved to prevent corrosion and improper wiring.
