Power Quality

Power Conditioning Equipment

Power conditioning devices are readily available to the homeowner to provide extra protection in the event of power disturbances. Appliances such as personal computers, VCRs, microwave ovens, or stereos may need protection from voltage spikes caused by storms, accidents, or nearby motors. A quality surge suppressor and noise filter may protect your most important and sensitive equipment from electrical disturbances.

In the long run, power-conditioning equipment can provide very effective and inexpensive insurance. However, remember that even the best power-conditioning equipment cannot always compensate for faulty wiring and grounding. Finding the right protective devices can be confusing. There are hundreds of systems on the market. Shop carefully for these devices and, if you have any questions after reading this article, talk with a reputable electronics or computer dealer. Nowadays, another good source of information is the Internet.

Surge Protection Devices

A plug-in surge protection device (SPD), sometimes referred to as transient voltage suppressor (TVSS), is the simplest, least expensive, and most commonly purchased power-conditioning device. The function of the SPD is to reduce the magnitude of voltage spikes to a level safe for your electronic equipment. Many models of SPDs will also provide a small amount of noise filtering. The SPD is plugged into a wall receptacle, and your electronic equipment is then plugged into the SPD. Simplicity of installation is what makes this device so popular among homeowners.

When purchasing a SPD, check the specifications of the product you want to protect to ensure it can be can properly powered and protected by the SPD. Having this knowledge will help you purchase the correct SPD for your application.

Some common specifications that you may see when purchasing a SPD are:

  • UL Listing - The SPD should have an Underwriters Laboratories (UL) 1449 2nd Edition listing Surge Suppression rating on its label. UL is the industry standard for safety of surge protection devices. Be aware that some manufacturers may label products UL tested or UL approved and this is not the same as being UL listed.
  • Clamping Voltage - The voltage level that your SPD will start to protect your electronic equipment. You will find SPDs in a wide range of Clamping Voltages ranging from 330V to 600V. A SPD with a 330V clamping voltage rating will usually offer you the most protection for a 120V receptacle.
  • Let-Through Voltage - The level of voltage that is passed through a SPD to the electronic equipment that is plugged into it.
  • Joule Rating - The commonly used definition of Joule Rating is the amount of energy the SPD can absorb before it becomes damaged. It doesn't quantify a level of protection to the electronic equipment that is plugged into the SPD.
  • Three-Way Protection - Three-way protection means that all of the wires in the receptacle that the SPD is plugged into will be protected. Common symbols that indicate three-way protection are: L-N, L-G, N-G, Line-Neutral, Line-Ground, and Neutral-Ground respectively.
  • Indicating Lights - Lights that show when power is available to the plug-in SPD and a status light that shows that the SPD is operational gives you peace of mind that the SPD is operational and protecting your electronic equipment.

Keep in mind that surges don't only damage your electronic equipment through the electrical lines. Surges can occur on any wire that is connected to your electrical equipment such as: TV cable, radio antennas, and telephone lines. To properly protect your investment, you must minimize surges from all possible sources.
For larger appliances (washers, ovens, and ranges, for example) with electronic displays or controls, it would be prudent to check with the manufacturer to determine if ample surge protection is built into the electronic power supply. Since these larger appliances require more power, a plug-in SPD may not be suitable for the application. In the case of certain models of ovens, for example, a 240 V, 50 A circuit may be required. A 240 V appliance also has a different plug configuration from that of a standard 120 V appliance. In this case, a hard-wired SPD may be required for suitable surge protection. This type of device should be properly sized and installed by a qualified electrician.

Noise Filters

Noise filters are designed to block characteristic noise patterns and allow only the desired power frequency to reach your equipment. The filters are available in various configurations at moderate cost. The most convenient way to buy filters is as part of a combined surge protection and noise filter package. Look for a filter rated for electromagnetic interference (EMI) or radio-frequency interference (RFI).

Uninterruptible Power Supply (UPS) Systems

Usually one of the most costly protective devices, an uninterruptible power supply (UPS)provides the best overall safeguard against the widest range of power disturbances. The length of time (usually in minutes) that a UPS system can keep your equipment running during an outage depends on the load your equipment draws and the capacity of the UPS backup battery. The capacity rating of UPS equipment is expressed in Volt-Amperes or VA.

Generally, five minutes of backup power is enough time to save information on your computer, and is probably adequate for most people. On-line UPS systems are preferable to standby units, which may not always switch fast enough. Many UPS systems are available with connections (such as serial 9-pin or USB) to your computer that will automatically power down your computer safely.

Because a UPS can be a significant investment, you may want help choosing an appropriate unit. Sales personnel at many quality electronics distributors or customer service personnel at your electronic equipment manufacturer should be able to help you. One easy method is to surf the Internet to compare all of the major UPS manufacturers on-line. Prices for UPS products that can power your personal computer vary from $75 to $150.

Power Conditions