Inspect Portable Tools and Extension Cords
Workers need to inspect extension cords prior to their use for any cuts or abrasion. Extension cords may have damaged insulation.
Sometimes the insulation inside an electrical tool or appliance is damaged. When the insulation is damaged, exposed metal parts may become energized if a live wire inside touches them. Electric hand tools that are old, damaged, or misused may have damaged insulation inside.
Wire Size and Ampacity
In terms of conducting electrical current, the size of the wire matters. Look at the following table detailing the change in current-carrying capacity of a wire in amps as its size changes. You'll notice two things: the amount of current a wire can safely carry, its "ampacity," increases as the size of the wire increases. However, the American Wire Gauge (AWG) designation of the wire decreases as the wire size increases.
American Wire Gauge (AWG) Copper Wire Table
| Copper Wire Size (AWG) | Diameter (Mils) | Area (Circular Mils) | Ampacity in Free Air | Ampacity as Part of 3-conductor Cable |
|---|---|---|---|---|
| 14 AWG | 64.1 | 4109 | 20 Amps | 15 Amps |
| 12 AWG | 80.8 | 6529 | 25 Amps | 20 Amps |
| 10 AWG | 101.9 | 10,384 | 40 Amps | 30 Amps |
| 8 AWG | 128.5 | 16,512 | 70 Amps | 50 Amps |
Notice that a #8 wire is twice the diameter, but four times the area of a #14 wire.
How to Pick an Extension Cord
The gauge of the wire determines the rating of a fuse or circuit breaker in amps. For example, a circuit wired with #14 copper will get a 15 amp circuit breaker and a circuit with #12 copper can get a 20 amp breaker.
It is also possible to create a fire hazard by overloading an extension cord. This occurs when too much current is flowing in a conductor that is not heavy enough for the electrical load in amps.
What Must Your Employer Do to Protect You?
The OSHA construction standard requires flexible cords to be rated for hard or extra-hard usage. These ratings are derived from the National Electrical Code, and your employer is required to make sure the cord is indelibly marked approximately every foot along the length of the cord.
- Examples of these codes are S, ST, SO, and STO for hard service, and SJ, SJO, SJT, and SJTO for junior hard service.
- Extension cords must be 3-wire type so they may be grounded, and to permit grounding of any tools or equipment connected to them.
- Limit exposure of connectors and tools to excessive moisture by using watertight or sealable connectors.
Knowledge Check Choose the best answer for the question.
8-7. As the American Wire Gauge (AWG) wire size decreases, the ampacity of the wire in free air or as part of a 3-conductor cable _____.
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