Electrical Systems: Are You Wired for Safety?
A properly functioning electrical system is an essential feature of a healthy and safe house. Since electrical systems are generally expanded and upgraded over the life of a house, safety hazards often arise due to amateur renovations and improper installations.
With the help of professionals, you can identify common flaws and take corrective action to protect against electrical shock and fire. You will also ensure optimal efficiency of your electrical system.
How electricity works
Voltage (volts or V) is the pressure between any two wires of an electric current. Most modern houses have two incoming voltages: 120 volts for lighting and appliance circuits and 240 volts for larger appliances such as stoves and dryers.
Current (amperage or amps) flows constantly back and forth through live and neutral wires (conductors) when an appliance is turned on, completing the electrical “circuit.” This is known as alternating current (AC). Most home lighting circuits are 15 amps, while larger appliances require 30 amps.
The amount of electrical current flowing through wire is affected by resistance (ohms), which is the capacity of a material to resist the movement of electricity through it. For example, the copper wire typically used in home wiring has low resistance, so that electrical current can flow easily. In contrast, the insulators covering the wire (e.g. rubber) have high resistance and thus resist the passage of current.
The amount of electrical power needed to make an appliance operate is called “wattage,” and is a function of the amount of current flowing through the wire (amperage) and the pressure in the system (voltage).
A circuit becomes overloaded when too much current flows, causing heat to build up and wiring and insulation to break down. When two bare wires touch, a “short circuit” occurs, which can lead to sparks and fire.
Circuit breakers and fuses are safety devices designed to prevent overloading of electrical circuits. They are located in the panel box, the distribution centre for branch circuits that carry electricity throughout the house. When the amperage at which they are set is exceeded, the fuse blows or the breaker trips, which shuts off the flow of electricity and stops the circuit from continued overheating.
Is your electrical service adequate?
The electrical service coming into your house must be sufficient to satisfy the power requirements of the various electrical appliances you will be using. Older homes often have an inadequate capacity because of the increase in electrical appliance needs over the years.
Any service less than 60 amps is inadequate and must be upgraded. Although 60-70 amps may be adequate for a small condo, the minimum electrical service for a normal size modern house is 100 amps at 110/220 volts. A professional inspection of the panel box will determine if you need more electrical service.
Common hazards and precautions
Wrong size fuses are often used to replace blown fuses, especially in older houses. When the amperage of a fuse exceeds the wire capacity and there is an overload on the branch circuit, the fuse will not blow but the wires will become excessively hot, increasing the risk of fire. A recommendation is to switch to circuit breakers if feasible, or to install special fuse holders that will only accept a certain size of fuse.
Missing ground wires is often a problem in older homes. In any house built in the 1960s or later, all outlets should be grounded to accommodate modern grounded (3-prong plug) appliances. A ground fault circuit interrupter is a recommended alternative to rewiring for grounding.
Ground fault circuit interrupter (GFCI). Incorporated into a circuit breaker or electrical outlet, this handy device shuts off the power to a circuit when it detects as little as .005 amps leaking. Adding a GFCI on a circuit with an ungrounded outlet will provide adequate protection from an electrical shock hazard. Most codes require their use on outdoor and bathroom outlets, wherever water and electricity may be brought dangerously close.
Lack of junction boxes is an indication of sloppy electrical work. If missing, they must be installed. Connections in branch circuit wiring should be made behind a wall inside a sealed junction box. Where wires are exposed, the damage of electrical shock and fire is increased.
Extension cord overuse can result in circuit overload and wire overheating because the cords cannot handle as much electricity as wiring. An adequate number of outlets should be provided to deter this practice. Outlets should be located every 12 ft. along a wall and spaced so that no point along the wall is more than 6 ft. from an outlet. Kitchen outlets should be placed every 6 ft. and never more than 36″ apart.
Knob and tube wiring is commonly found in houses built before 1950. The conductor wires run separately of each other, whereas in modern cable the wires are wrapped together. The ground wire is missing and no junction boxes are used.
Knob and tube wiring is not in itself unsafe, but problems such as pinched wiring and damaged installation often arise from unskillful connections made during renovations. Because of this, insurers may insist that it be replaced with modern grounded electrical wiring.
Reversed polarity occurs when the live and neutral wires are improperly connected inside an outlet, again usually the result of do-it-yourself renovations. This can compromise the safety and/or proper functioning of an electrical appliance and must be corrected.
If you have any concerns about the safety of your electrical system, it would be wise to hire a professional home inspector. And whenever electrical circuits are added or changed during home renovations, be sure to use a licensed electrician whose work complies with the BC Electrical Code.