A surge protective device (SPD) is a piece of equipment designed to protect electrical devices from an electrical surge or power surge. A power surge is an intense, short duration voltage increase that travels through electrical wiring or other cables that transmit data or energy, such as phone lines and coaxial cables. If a power surge occurs, the SPD is designed to limit the voltage supplied to an electric device by either blocking or shorting to ground any unwanted voltages above a safe level. Some common causes of surges include:
- Lightning strikes
- Tripped circuit breakers
- On/off cycles of large appliances and tools within the home
There are two types of SPD's available; whole home hard-wired devices and plug-in devices (power strips). SPD's are rated in Joules and Clamping Voltage. The Joules rating tells you how much energy dissipation the SPD is capable of. The higher the Joule, the better. The Clamping Voltage refers to the amount of voltage that will cause the SPD to start protecting your electronic devices. The lower the clamping voltage, the better the protection.
The whole home hard-wired devices are installed at the electrical panel and the plug-in devices are for point of use, such as a TV, computer, microwave or other plug in devices. To provide the home with the most protection, it is recommended to use both types of devices. Most homeowners can easily install the plug-in devices, but a licensed and qualified electrician may be needed to install the whole home hard-wired device because it requires working in the electrical panel.
There are several manufactures of SPD's. Most all are sold in hardware stores, electrical supply distributors, major chain stores and available on line. Most hard-wired devices start in price around $60 and the plug-in devices start around $30. The more expensive devices typically carry better warranties and provide better surge protection.
Some helpful tips in selecting and installing an SPD for your home are:
- Ensure the SPD is rated by Underwriter's Laboratories, Inc. The standard category is 1449.
- It is very important to have a properly installed SPD. A good SPD, incorrectly installed has no benefit.
- Choose an SPD with enough Joules and clamping voltage to properly protect your home and electronic devices.
- What type of warranty comes with the SPD?
- Look for SPD's that have indicator lights to let you know the device is functioning properly.