Electrical Grounding Q&A

QUESTION

“I have an older home with the old style, two pronged outlets that are not grounded. I’m concerned about having my electrical system properly grounded, but I don’t really understand how a grounding system works. All I know is that it is supposed to prevent you from getting shocked. Would you tell me a little bit about it?” – R.P., San Mateo

ANSWER

Grounding an electrical system is more than just driving a grounding rod and connecting it to the main panel. It is a matter of providing a path of least resistance for electricity to return to its source, to prevent it from traveling back through our bodies, outlets, and appliances. To understand grounding, it is important to know how electricity works, and how it travels through a house’s electrical system.

Electricity can basically be broken down into two elements, voltage and amps. A good analogy for electricity is pressurized water in a pipe, like the water lines in your house. Water is similar to the electron flow in an electrical current. As water flows through a pipe, the electrons in an electrical current flow through a wire, or any similar conductive material. Voltage is similar to the water pressure in the pipe, and amperage is similar to the volume of water that comes out the end of the pipe. The common voltage for residential construction is 120/240 volts, and the common amperage is 100 amps.

The one golden rule about electricity is that it always wants to get back to its source. That is why electrical systems need to utilize at least two wires, a hot and a neutral. The hot wire is the one that carries the current to house, and the neutral wire is to provide a return path to the utility or source of the power. Unfortunately, this is not a completely safe system because electricity has the ability to travel through other conductive objects as well as the ground we stand on. The grounding portion of an electrical system is designed to provide a safe, alternate path for electricity to travel back to its source, without the possibility of traveling through a person or an object.

The grounding system for a house, starts at the main panel. In the main panel, there are usually two hot conductors, each 120 volts, that supply the electrical power to the panel, and there is also a neutral conductor that acts as the return path back to the utility. Since the neutral conductor is the dedicated source back to the utility, all potential paths that an electrical current can travel on, need to be connected or “bonded” to this neutral wire.

This is accomplished by connecting a “grounding wire (usually just a bare copper wire), to all of the panel boxes, outlets, appliances and metal pipes in the house, and connecting the other end to the neutral in the main panel. The interesting thing about this connection to the neutral line is that this is only done in a main panel, and not in a sub panel. In a sub panel, the neutral wires and grounding wires must be kept separate, and not connected together. This is why the neutral buss bar located in a sub panel, is isolated from the ground connections by plastic insulators.

If the neutrals and grounds are connected together in a sub panel, and there was a short to the ground, the electrical current would have the ability to travel through other circuits in the house, potentially injuring a person in another area.

Many accidents occur ever year where someone is electrocuted by touching the metal housing of an appliance, metal water line or metal furnace ducting, because an electrical current from a short, was running though it. The current in these items was just waiting for a path back to ground, and in each case, the person touching the item, provided that path. A person’s safety is the most important reason to have a properly grounded electrical system.

To properly ground an electrical outlet, you need to connect one end of a ground wire to the base of the outlet, to the green screw, and the other end to grounded surface. If your house wiring contains a grounding (bare copper) wire, it is probably attached to the metal wall box that houses the outlet. In this case, you can connect the ground wire from the outlet directly to the box. This can be done with either a special screw or clip.

If there is no grounding wire in the wiring, you must run a ground wire to another grounded surface such as the electrical sub panel, or a metal water pipe that has been connected at some point, to the grounding system. This is the only way to guarantee that there is an alternate path for electricity to flow back to its source.

Whenever you are dealing with electricity, it is always best if you consult with a competent electrical contractor. Properly grounding an electrical system is not difficult, but it can be very technical, and there are a lot of specialized fittings and hardware. If electrical work is done incorrectly, or carelessly, it will not provide the protection it should.

Aluminum Wiring Q&A

QUESTION

“We just inherited a 45-year old house, and shortly after we moved in we noticed that the lights would occasionally flicker on and off. Some switches were hot to the touch. I contacted an electrician to come over and inspect the wiring. He said that the problem was with the aluminum wiring used in my house. He showed me burn marks at some switches and outlets. He said that I should have the whole house rewired and that can cost thousands of dollars. My parents were the original owners, and I don’t remember them ever having a problem. How much of a concern is it to have aluminum wiring in the house?” –  D.S., San Mateo

ANSWER

Aluminum wiring has been used for many years in residential construction and is still being used today. Properly installed, it is as safe as copper wiring. In fact, you will probably find it (to some extent) in more than 90% of the homes, condominiums and apartments being built today.

The fears and concerns about using aluminum wiring usually dates back to the late 1960’s, because aluminum wiring got a lot of bad press. There were several cases where electrical fires had been occurring in houses built with aluminum wiring. In some homes, people would have switches and outlets getting hot when in use, and sometimes causing shocks to individuals, or starting fires.

Before the 1960’s, most homes in California were wired with copper wire. It was cheap and easy to work with. Then in the early 1960’s the price of copper had gone way up, and contractors building large housing tracts turned to using aluminum wiring as an alternative. PG&E had been using aluminum wiring for years and never had any problems.

What the contractors did not understand at the time, is that the characteristics of aluminum wiring are very different from that of copper, and that there were specific installation standards that had to be followed when using it. Investigations that followed all of these fires were able to prove that it was not the wiring that was the source of the fires, but rather the workmanship of how the wiring was installed.

Aluminum wiring is soft, has a low melting temperature, expands when heated and oxidizes easily. Because of this, aluminum requires that any connection to it be made in such a way that the wiring will not be able to loosen. This is usually done with a special crimping tool and special connectors. Copper wire on the other hand, is a little more stable and flexible than aluminum wiring, and does not require the special connectors

The secrete to living with, and using aluminum wiring, is making sure that it is properly installed with the proper connections. The National Electrical Code requires that any fitting connected to aluminum wiring be approved for use with that type of wiring. This basically means that you cannot connect an outlet, switch, fixture or fitting to aluminum wiring unless it is rated to be connected with aluminum wiring. These devices should be clearly marked with the designation “CU/AL” or “CU/ALR”. This means that the fitting is approved for use for copper (CU) and aluminum (AL). The “ALR” designation means aluminum residential.

What happened back in the 1960’s is that the installing contractors were connecting the aluminum wiring to outlets, fixtures and switches that were designed to be connected to only copper wiring. The fact that your house has aluminum wiring should not pose a safety problem if it is properly installed.

Your question seems to indicate that the problem with the wiring is at the joints or connections to the switches and outlets. This is where most of the problems occur with aluminum wiring. Because aluminum wiring expands and contracts a bit when an electrical load is running through it, it tends to heat up and loosen connections if it is not properly tightened. This usually results in a switch or an outlet being warm or hot when touched. Over the years, this overheating tends to damage outlets and switches. Merely replacing these devices will fix the problem in most cases.

To ensure the safety of your electrical system, you should have it inspected by a qualified electrician. Start by having the electrician inspect all your outlets and switches. It is possible that there is a loose connection at some other area, such as a light fixture, junction box, or sub panel. In any case, a good electrician should be able to trace down all of the problems.

Arc Fault Circuit Interrupters (AFCIs)

A new electrical safety device is now being required in the State of California, and it is called an Arc Fault Circuit Interrupter (AFCI). Since 2003, it has been required to be installed on all bedroom circuits for new construction. This device has the ability to “sense” and detect overheating and shorting of electrical wiring that could start a fire, but would not trip a standard breaker. What’s interesting is that it has taken almost ten years of research and development for this device to be required in residential construction.

In 1992, the Consumer Products Safety Commission initiated the “Home Electrical System Fires Project”, and contracted with Underwriters Laboratories to provide research and evaluations on electrical fires in homes. The research revealed that arcing and overheating of a home’s electrical wiring are associated with more than 40,000 home fires each year, that claim over 350 lives and injure more than 1,4000 individuals.

Arcing occurs when electrical wiring is nicked or damaged, or when there is a loose or poor connection. Nails from installing pictures, wood trim or cable wires can damage electrical wiring. Damage can also occur at power cords caught in doors or under furniture or rugs, plugs in outlets being pushed against by furniture, or cords that are exposed to extensive sunlight or heater vents. Loose joints and poor connections occur outlets or switches or partial breaks in the wiring. All of these conditions can cause arcing, and create high temperatures that can cause fires.

Arcing is dangerous in that it often goes undetected for extended periods of time. It usually begins where it is not easily seen, such as in an extension cord running under the carpeting, at a worn light switch or wall outlet, or at a wiring connection that is no longer tight. In a split second, arcing can create temperatures as high as 5000 degrees Fahrenheit at low current levels. Unfortunately, regular circuit breakers do not respond to signs of early arcing but are rather designed to trip when there are excessive loads and short circuits. They will not trip off when arcing and overheating of electrical wiring produces small differences in the flow of current.

AFCIs are designed to differentiate between normal and unwanted arcing conditions by continuously monitoring current flow. Normal arcing can occur when a switch is opened or a plug is pulled from a receptacle. This is not the type of arcing that usually causes fires or serious electrical concerns. However, unwanted arcing (high heat producing) takes place when conductors touch and separate, resulting in sparks and overheating. When these conditions happen, they are detected the AFCI, and it immediately trips, shutting off the power, and prevents fires from occurring.

The currently adopted edition of the 1999 National Electrical Code in California, requires all electrical outlets in bedrooms of new construction be protected with AFCIs.

Research has shown a large percentage of electrical fires and injuries occur from arcing wiring in bedrooms. Although the electrical outlets in bedrooms represent only a few of the circuits in the house, future editions of the code will require them in other areas and applications.

The good news for the consumer is, this important safety device is relatively inexpensive to install. It can easily be added to most electrical systems in existing homes to provide additional protection for older, and possibly deteriorated wiring.

There are two basic types of AFCI devices currently being used in residential construction. The first type is a circuit breaker that is installed in a main or sub electrical panel of a home. The second is an outlet that is connected directly onto the wiring of a wall outlet. AFCIs can be installed in any 15 or 20 amp branch circuit in the house. Although the installation of either device is relatively straight forward, it is best to consult with an electrical contractor to ensure the devices are properly connected.

It is important not to confuse the ACFI with ground fault circuit interrupters (GFCIs). GFCIs have been required in residential construction since the mid 1970’s. The most common type of GFCI is a circuit breaker or an outlet with the two little push buttons built into the middle of the device. They are usually installed in bathrooms, garages, and kitchens. GFCIs are designed to provide user protection from electrical shock from ground faults.

Electrical shocks from ground faults occur when an unintentional electrical path is created diverting the current to the ground. If this electrical current is allowed to travel through a person’s body, he or she could be severely shocked or electrocuted. GFCIs are not designed to react to hazardous arcing faults that can cause fires, but AFCIs are. Realizing the potential of combining these safety features, manufacturers are already designing devices that have both forms of protection built into one device.

Anyone thinking of updating or adding onto their electrical system, should seriously consider installing this valuable safety device.