Electrical wiring is frequently one of the most intimidating home improvement tasks for a DIY home owner, with good reason.
There are real and present dangers inherent in electricity and electrical wiring, but these dangers are, in reality, no greater than the dangers present in some of the carpentry tasks more commonly attempted by the avid do-it-yourselfer.
The stability of a deck is every bit as much a safety concern as the integrity of your wiring, and falling off a roof is statistically far more likely to cause injury than electrical shock.
Still, DIY homeowners are more likely to build a deck or work on a roof than wire a new circuit, because many people feel they don't have a proper understanding of electrical wiring. This article offers information that can help a DIY homeowner attempt electrical wiring in a safe and professional manner.
The first half offers safety tips for while you are working with wiring. The second half offers tips to help ensure that your wiring will operate safely when completed.
Basic Safety for Electrical Work
Turn off the Power:
Make sure the power to any wires near where you are working is turned off. Turn off the power at the circuit breaker panel. Do not simply turn off a switch to a light. A no-touch voltage tester can further ensure that there is no power in the wires you are working on. Rooms often have more than one circuit, making it more difficult to know if you turned off the correct breaker. A quick touch of a button on these inexpensive testers will tell you if the wire is live or not.
Cover the breaker switch with tape:
Once you have established that the power is off, cover the breaker switch with a piece of tape. This will help prevent anyone else from turning the power back on while you are working.
Work with one wire at a time:
You can't get shocked unless you touch the hot and neutral wire at the same time, even if the power is on. You should never work around wires while the power is on, but avoiding contact with both hot and neutral wires simultaneously will further diminish the chances of an accident.
Use approved electricians' tools:
All electricians' tools, from screw drivers to pliers, come equipped with rubber handles. This doesn't make it safe to work with live power, but it is an important last line of defense in case something does go wrong.
Basic tips for Safe Home Wiring
Use the correct size and type of wiring:
Home wiring should be solid copper wiring with the hot and neutral wiring wrapped in rubber insulation. The hot, neutral, and bare ground wire are then wrapped together with another coating of rubber insulation. (This is a description of Romex wiring. Some cities will require BX wiring that has a flexible metal shell around the wiring set.)
Extension cords are made with braided copper wiring. These should never be used for home wiring. Wiring is also categorized by the gauge of wire and the number of wires in a set. 12/2 wiring with ground, for example, is twelve gauge wire with two wires (hot and neutral) and a bare ground wire.
The gauge of wire is very important for the safe operation of your wiring. Circuit breakers function primarily due to the resistance in the wiring. The resistance is determined by the thickness and length of the wiring. Most appliances and light fixtures will specify what size wiring they are rated for in the manual. Make sure you meet at least this minimum rating. (If you are running an exceptionally long stretch of wires it's usually a good idea to go with wiring one size thicker.)
Secure wiring with approved cable staples:
Wiring will function fine if it is run loose, but the potential movement can lead to torn rubber insulation or loose connections. Secure the wiring with cable staples every few feet and at least six inches from any electrical box where movement will easily loosen the connections. (Leave the cable staples slightly loose to avoid damaging the rubber insulation.)
Discard any wires with torn insulation:
Wiring is unacceptable if the rubber coating is torn or damaged in any way. Even if the individual wire insulation is intact, torn wiring should not be used. Use approved electrical boxes for all junctions and receptacles: Junction and receptacle boxes are designed to add an element of protection in the event that connections become loose or wire exposed. Open wiring connections are a significant fire and electrical shock hazard.
Keep all junctions and receptacles accessible:
Outlets, switches, and light fixtures are accessible by nature, but homeowners will often hide a junction box behind drywall. This is an extremely unsafe practice. Mechanical wiring connectors can work themselves loose and lead to problems if made inaccessible. (If you absolutely must cover a junction box, the connections inside the box should be soldiered together and covered with heat-shrink insulation and electrical tape.)
Use approved connectors for all wiring connections:
Do not splice wires together by twisting them and covering with electrical tape, even inside a box. Wire nuts and other approved connectors are designed to reduce the risk of fire or shock.
Ground all metal boxes:
Metal electrical boxes that are not grounded can become electrified themselves if something goes wrong. Anyone touching the outlet or switch can be shocked. Connect the bare ground wires to the grounding screw (green screw) in the back of the box. If there is no screw in the box, use a self tapping screw to create a grounding screw. Plastic boxes do not need to be grounded, but the bare ground wires should be tied together at every connection to create a solid ground for the circuit.
Cover exposed wire with electrical tape:
Do not use electrical tape to cover damaged wire, but you will need to expose the ends of each wire inside the boxes. Wrapping the connections on switches, outlets, or fixtures with electrical tape after the connections are made will add an extra line of defense.