Don’t Be Shocked by Home Wiring Problems

The Question: I was told that some of the wiring in my home is dangerous and should be replaced. What should I do?

Bill Shea of William J. Shea Electric
Bill Shea of William J. Shea Electric

The Answer from Bill Shea of William J. Shea Electric: Yes, it is very possible that some of your wiring in your home is dangerous, faulty and should be replaced.

Electric wiring in older homes ranges from perfectly usable to downright dangerous. Not only could old insulating material rot and expose hot wires, but systems that were designed to support a few lights and radios are now being asked to power computers, microwaves, hair dryers, refrigerators and many other modern devices. Before purchasing an old home, or if you suspect aging or faulty wiring, call an expert to evaluate the entire electrical system. I have listed a few types of residential wiring throughout an average home and remedies to create a safe electrical system.

Knob and Tube
In this wiring system, porcelain “knobs” hold the wires in place as they stretch through open spaces within walls. Porcelain “tubes” direct wires through studs and joists. This system was common in homes built before about 1930, and many homes dating to this era still have the original knob-and-tube wiring in place. The wiring, splices and worn insulation are causes for concern. I highly recommend replacement of this type of wiring.

Armored Cable
Knob-and-tube wiring was replaced with armored cable. In this system, hot and neutral wires run through a flexible steel sheath, which provides a ground connection. The wires inside are insulated with rubber covered in cloth. According to This Old House, homeowners should check the insulation about every five years and should ensure that the steel sheath is properly connected to a metal outlet box. If you notice rust or the cable glowing, it’s best to have those cables replaced.

Nonmetallic Cable
You probably will buy and work with nonmetallic plastic-sheathed cable more than any other conductor or wire. It is often called by a trade name, Romex, which has almost become synonymous with any non-metallic electrical cable. Local codes may allow nonmetallic cable only in certain locations, or may specify that you use another type, such as metallic armored cable, or wires running in conduit.

The outer sheath of nonmetallic cable is usually a moisture-resistant, flame-retardant material. Inside, there are two or three insulated power wires, and perhaps a grounding wire. For most residential wiring, two types are often used.

*Type NM—This is based only in dry locations. Each wire, with the possible exception of the ground wire, is wrapped in its own plastic sheath. The three wires are then wrapped in a paper insulator, and the wrapping is covered with plastic. The wire in Type NM is either AWG No. 12 or AWG No. 14 for house circuits. Larger sizes such as No. 10 or more are used for heavy appliances. NM is available in two or three conductors, plus the ground.

*Type UF—For use in wet locations, including underground, UF cable is an alternative to conduit. The cable has individual wires embedded in water-resistant solid plastic. The cable is available in AWG No. 12 and No. 14, with the ground.

Two-Wire Plastic-Sheathed Cable
This early version of the modern ROMEX® cable consists of wires sheathed in plastic. The plastic can be easily damaged. Because it contains only two wires, it is impossible to add grounded devices to this system. This cable type should be replaced . The ground wire is the most important conductor in a cable. It helps from you being ELECTROCUTED!!!

Aluminum Wire
Aluminum wire does not necessarily need to be replaced, but it is more likely to cause problems than other types and must be inspected and maintained. Problems can occur at connections, and if this has happened in the past the homeowner will often see signs of arcing in switches and outlets. Flickering lights and a distinctive smell of burning metal also indicate a potential problem. This type of wiring usually dates to the 1960s and 1970s. You should either replace this wiring or have the outlets and switches pigtailed.

Pigtail repair method involves attaching copper wire to the existing aluminum. Pigtailing uses special twist connectors compatible with both aluminum and copper. While the pigtailing parts are inexpensive and readily available, the pigtailing technique requires specialized knowledge and experience. Furthermore, although pigtailing is cheaper than the COPALUM system, its success depends entirely on how well the electrician executes the repair. It is difficult to get a good connection that will not oxidize, making long term safety an issue. Some believe that a poorly executed pigtail is worse than doing nothing.

If you feel that any of the above wiring examples are in your home and just don’t feel comfortable with the old wiring, you can call William J. Shea Electric to have a technician come out and advise you of your options. You can contact William J. Shea Electric at 631-668-1600 or or visit their website at Remember, always do it “THE SHEA WAY”—the safe way!!! 


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