Things Redi Kilowatt Never Told Us
By Don Carter, Structural Engineer
Kansas Senior Press Service
A Project of the KU Center on Aging
I have heard firemen say that after a house fire is extinguished, investigators are tasked to identify the source. When all other sources are eliminated, the home’s electrical system is blamed. Stated another way, after the heating system, lightning, cigarettes, explosion, arson et al are ruled out, electrical becomes the default source of all house fires. According to the American Red Cross, 1,200 senior citizens a year die in house fires. In this and future articles I’ll address the fundamentals of your home’s electrical system with special emphasis on safety.
Panel Boxes
Electricity comes to our homes by way of a wire, either overhead or below ground, from a utility line in the yard. The wire delivers electricity to a meter, which records usage and becomes the basis for our light bill. The meter sends a wire through the outside wall to a metal enclosure known as panel box or power panel. Older homes, say pre 1960, typically had fuse boxes while newer homes use circuit breakers. Circuit breakers switch off and on, while fuses stop electrical flow by melting and so must be replaced when they fail. Either way, they are the safety valves that sense problems and shut down electricity before disaster happens. The panel box is Mission Control for everything in the house that uses electricity.
All household members should know where the main power switch is located, in case of an emergency such as a fire or basement flooding. Even though it is not required, the most logical place for that main switch is at the panel box. Sometimes, however, the main switch is located in a separate box, even at a separate location. Some older homes have fused pull-outs; others have a lever that you pull to shut off the main power. In the latter case, you also have to pull that lever to change a fuse, which protects you as well. Still others have a circuit breaker switch or button. Whatever the set-up of your power panel, you will be able to operate the main switch without being exposed to live electricity.
Keep in mind how dangerous it is to work at the panel box if the main switch is not turned off. The amount of electricity being brought into the house can easily kill. If you are unfamiliar with your box, or if you don't know where the main switch is located, have a professional explain how to work with your particular box.
If circuit breakers or fuses trip, that is a sign that something is overloading the related circuit. Is it the appliance, or is it the circuit? Find out where the problem lies, and correct it.
I have seen basement walls leaning inward to such a degree that the panel box, once flat against the wall, is pushed out at an angle. When this happens, wires get stretched and can readily disconnect or break. Look at your box to confirm that it is flat against the wall mount.
Sometimes people use a copper penny to replace a blown fuse, intending to remove it and install a new fuse at their earliest convenience. Check your box to be sure that all fuses are fuses. If you have a fuse box, consider having it changed out to a circuit breaker panel with at least 100 Amp capacity. The problem with fuses is that you can install whatever size fuse won’t blow, and then seriously overload the wiring.
Circuit breakers with screw connected wire posts often relax after a period of time. If you have a breaker that trips without obvious provocation, shut off the main and check the screw connections to be sure they are tight. I have twice had breaker problems that were nothing more than loose screws.
If a tree limb or ice knocks down the incoming power line, have the electrical panel box checked by a competent inspector before turning the power back on. If you can see any exposed wires at the meter or meter box, have that checked and repaired. The power company may repair defects on their side of the meter, at no charge.
Some material for this article was obtained from www.doityourself.com.
WIRING
Editor’s note: On May 12, 2004, KSPS sent out the first part of this series on electrical safety The purpose of these articles is to address the danger of house fires caused by faulty electrical performance.
We previously characterized the electrical panel box as “mission control,” the place where electricity enters your house then breaks out into multiple zones, each protected by a circuit breaker or fuse. I had an instructor who taught electricity by using a water analogy, and I borrow his comparisons for this series. Think of circuit breakers as drinking cups. A 10-ounce cup holds 10 ounces and no more. Try to force 11 ounces in it, and the cup is overwhelmed. Likewise, circuit breakers accommodate their designated capacity (amps) and beyond that they are overwhelmed and shut down.
In a typical home, the panel box may easily have 24 circuits, thus 24 wires leave that box to run under floors, over ceilings and through walls to outlets and switches. Just as the circuit breaker compares to a drinking cup, wires work like water pipes with amps flowing through them instead of water. Like pipes, wires are capacity limited.
Copper is the most commonly used material for wires, however in this segment we want to talk about aluminum wiring because it has some unique risks that merit early discussion.
Aluminum wiring
During the 1970s, aluminum wiring became popular and was used in a lot of applications. Since that time, aluminum wiring has been implicated in a number of house fires and has thus dropped out of favor. Many local codes won’t even allow aluminum wires in new installations. If you have aluminum wiring, you must be aware of its limitations and make certain it is properly installed and maintained. Aluminum wiring’s big problem is something known as “cold creep.” When the wiring warms up it expands, then when it cools it contracts. Unlike copper, aluminum loses tightness as it goes through multiple warm/cool cycles. To make matters worse, aluminum oxidizes (corrodes) when in contact with certain other metals and these problems can collectively lead to a temperature hot enough to melt insulation. If you have aluminum wiring, please look carefully at your system and heed the following tips :
1. Fixtures (outlets and switches) directly attached to aluminum wiring should be rated for it. The device will be stamped with “Al/Cu” or “CO/ALR”. Both are safe.
2. Wires should be properly connected with at least ¾ turn around the screw in a clockwise direction. Connections should be tight. While repeated tightening of the screws can make the problem worse, during inspection it would pay to snug each connection.
3. Push-in terminals are an extreme hazard with aluminum wire. Any connections using push-in terminals should be redone immediately with proper screw connections.
4. Look for signs of overheating such as darkened connections, melted insulation, or “baked” fixtures. All observed damage must be repaired.
5. Connections between aluminum and copper wire need professional involvement.
If you observe any of these distress signs or have findings of non-compliance, play it safe and call a licensed electrician for evaluation. As the old slogan goes, “the life you save may be your own.”
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