AROUND THE CIRCUIT

Protect Your Appliances from Surge

Voltage surges, also known as power surges, are considered to be the most destructive of all electrical power disturbances. A voltage surge is a brief increase (spike) in voltage, usually lasting for a small fraction of a second. They vary in magnitude from a few hundred volts to several thousand volts. Since a significant increase in voltage above the normal operating voltage of an appliance can cause catastrophic damage to the appliance, we need to protect our expensive and sensitive appliances against surges.

Voltage surges occur in any electricity system. They can originate from outside your building due to lightning, switching operations by the electricity utility, and switching of high-power equipment in nearby commercial or industrial facilities. They can also originate from within the building when appliances such as air conditioners and refrigerators are switched, or cycled on and off during operation. Large surges may cause instantaneous failure to appliances. However, the smaller repeated surges may gradually erode sensitive electronic components in your appliances, eventually leading to failure. To protect appliances against damage from surges, devices called surge suppressors are used.

How does a surge suppressor protect your appliance? A standard surge suppressor looks somewhat like a extension power cord with multiple outlets on a power strip (see picture right). The surge suppressor is plugged into a regular wall outlet to pass electricity to a number of electrical and electronic devices which can be plugged into its power strip. If there is a surge (an increase in voltage above an acceptable level) in the electricity supply, the surge suppressor diverts the majority of the excess electricity to ground, and away from the connected equipment. In order for this to happen, the outlet into which the surge suppressor is plugged must be properly wired and grounded. Some electricians do not ensure that building outlets are properly wired and grounded. Fortunately, many surge suppressors carry indicating lights that alert you of grounding or other wiring problems in the power outlet. If your surge suppressor gives you any such indication, get the wiring checked and corrected by a competent, certified electrician. Otherwise, the surge suppressor will not provide effective protection to your appliances.

There are three basic things to look for when choosing a surge suppressor:

1. The UL1449 (or similar) Rating: This Underwriters Laboratories rating is the standard for surge suppressors. It ensures the suppressor can reduce a surge of several thousand volts to a harmless 330 to 400 volts.
2. Energy absorption/dissipation: This rating (given in Joules) tells you how much energy the surge protector can absorb before it fails. A surge protector rated 600 Joules or more is usually recommended.
3. Internal Tripping Device: When surge suppressors are subjected to a power surge that last longer than they are designed to handle, the tripping mechanism (usually a thermal fuse or breaker) breaks the circuit, preventing the surge from reaching connected equipment.

Be aware that thermal fuses provide protection by rupturing. As such, they would need replacing after they have operated.