S A F E T Y M O D E L S TAG E 1 — r E C O G N I Z I N G H A Z A r D S
Inadequate wiring hazards
❚ wire gauge—wire size or diameter (technically, the cross-sectional area)
❚ ampacity—the maximum amount of current a wire can carry safely without overheating
❚ Overloaded wires get hot!
An electrical hazard exists when the wire is too small a gauge for the current it will carry. Normally, the circuit breaker in a circuit is matched to the wire size. However, in older wiring, branch lines to permanent ceiling light fixtures could be wired with a smaller gauge than the supply cable. Let’s say a light fixture is replaced with another device that uses more current. The current capacity (ampacity) of the branch wire could be exceeded. When a wire is too small for the cur- rent it is supposed to carry, the wire will heat up. The heated wire could cause a fire.
When you use an extension cord, the size of the wire you are plac- ing into the circuit may be too small for the equipment. The circuit breaker could be the right size for the circuit but not right for the smaller-gauge extension cord. A tool plugged into the extension cord may use more current than the cord can handle without tripping the circuit breaker. The wire will overheat and could cause a fire.
❚ Incorrect wiring practices can cause fires!
The kind of metal used as a conductor can cause an electrical haz- ard. Special care needs to be taken with aluminum wire. Since it is more brittle than copper, aluminum wire can crack and break more easily. Connections with alu- minum wire can become loose and oxidize if not made properly, creating heat or arc- ing. You need to recognize that inadequate wiring is a hazard.
Exposed electrical parts hazards
Electrical hazards exist when wires or other electrical parts are exposed. Wires and parts can be exposed if a cover is removed from a wiring or breaker box. The overhead wires coming into a home may be exposed. Electrical
❚ If you touch live electrical parts, you will be shocked.
This hand-held sander has exposed wires and should not be used.