Electrical System and Panel

By Frank G. Ross

Electrical systems can seem like a confusing mess of connections, cables, and boxes hidden inside the walls.  What seems complex at first can be understood with a simplified explanation.

A local utility supplies electricity to a home through three wires (two "hot" leads and one neutral lead) that enter the house (underground or overhead) through a conduit and a meter.

Those wires enter the service panel to connect to their respective buss bars inside -- usually two hot, one neutral, and one ground buss. Circuit breakers cover the hot buss bars. Their role is to act as a safeguard against short circuits and overloads by "tripping" when a dangerous condition arises. Homeowners should know how to reset a breaker.  Usually it must be flipped to the “off” position before being turned back on. Additionally, power can be turned off or on as desired using the breaker as a switch.

Older homes may have a fuse panel.  Fuses will be either a round screw-in type or the larger cartridge type mounted in a fuse block that can be pulled from the main panel.  For greatest safety, blown fuses must be replaced with the correct amperage rating.  Although a larger amperage fuse may fit the socket, it will not protect the circuit properly.  In one home I inspected with the cartridge type fuses, the homeowner had replaced a blown fuse with a length of copper tubing.  The electrical system may function like that, but without the protection from the fuse, it is also a fire hazard.

Electricity is distributed throughout the home by "hot" wires leaving the main panel to deliver power to a device (like a light fixture).  These hot wires normally have black insulation. If a cable is the type with two hot leads it will also have a red hot lead.

A circuit is complete when the electricity has traveled from the device back to the panel.  It does this using a "neutral" wire, which is most often white. Electricity needs this completed circuit to work properly -- a way from the service panel through the hot wire, and a way back to the panel through the neutral wire.

 
The ground wire, which is usually green (or bare copper), offers the electrical current another path back should an electrical short or overload occur. At the service panel, the ground often has two safe paths to divert electricity: to a long metal rod buried outside the house (the grounding rod) and/or the home’s water pipes.

Cable, the trade name for electrical wire, usually comes covered by a flexible plastic sheathing. Technically, it's nonmetallic-sheathed (NM) cable, but it is often mistakenly called by the brand name "Romex" (which is made by General Cable Corporation)  the same way facial tissues are often referred to as “Kleenex” or a photocopier is known as a “Xerox” machine.

Cable is also identified by gauge (thickness) and the number of leads it has. For example, NM 14-2G means that the cable is nonmetallic, 14 gauge, has two leads (1 neutral, 1 hot), and a ground wire.

Properly installed electrical systems are very safe and efficient.  Some basic knowledge on the part of homeowners can help prevent safety problems, though.  Homeowners should know where the main electrical disconnect is located and how and when to use it.  It is helpful to have the breakers or fuses clearly labeled in the main panel.  Identify which breakers or fuses control which outlets.  Also, know which outlets are GFCI protected.  Ground Fault Circuit Interrupters are sensitive to tiny imbalances in the power and neutral wires and will trip when an imbalance is detected.  They are important safety devices which should be installed wherever electricity is needed in potentially wet environments such as in bathrooms, kitchens, or outside.  Test GFCI outlets and breakers monthly.

There are many configurations and combinations of components possible in a home’s electrical system.  I’ve shared just the briefest of overviews.  Never attempt an electrical repair unless you know exactly what you are doing.  If you're not confident in your ability to do electrical work, continue to learn more about it or consider hiring someone to do the work.

Frank Ross is a Certified Utah Home Inspector for Pillar to Post Professional Home Inspection and a full member of the National Association of Certified Home Inspectors and a member in good standing with the Utah Better Business Bureau.  Readers may contact Mr. Ross at (435) 867-6400 or frank.ross@pillartopost.com