Surge Protection System
The major drawback to a lightning protection system is that lightning rods cannot stop electrical surges from coming into a house through utility lines, which is the most common way that lightning damages homes. Transient electrical currents from telephone, cable, and telecommunications lines can cause undesirable surges in voltage. The magnetic field created by a lightning bolt can cause voltage to flow through any conducting material such as the wiring or metal piping in your home. Therefore, an effective surge protection system is a necessity in every home, if it is to be safeguarded against these kinds of potential disruptions.
Many people install low-cost surge arresters, or suppressors, that plug directly into an outlet, believing they are providing themselves with whole house protection. Unfortunately, this is not the case. Surge suppression must be accomplished on two levels. First is at the main panel, where the surge can be prevented from entering the house wiring, and the second is at the point-of-use, where any surge remaining on a line can be removed just before it enters an appliance or other electrical device. Clearly, it makes sense to use a surge arrester to eliminate heavy surges before they enter your home, rather than after. A surge arrester will divert heavy electrical surges into your grounding system, permitting your point-of-use devices to serve as sensitive electronic filters, shutting down noise on the line, as well as stopping any remaining line surges. If your home has a sub-panel located 20 feet or more from the main panel, you should install a second device to protect it, too. In addition, some lightning protection systems may have a box devoted solely to the system that can be mounted adjacent to the main panel. This type of box contains modular electronics that are replaceable should they be destroyed by a lightning surge passing through the box. In effect, the box is sacrificed to protect your home.
Surge arresters may be directly wired to the main panel and mounted either on the inside or outside of the panel box. The type that mounts outside the panel box is usually preferred in order to protect the breakers and curcuits from explosive discharge. A better system for containing lightning surges, and the easiest to install, is a whole-house protection system in which the surge arrester replaces a circuit breaker in the main panel. Because you have to have a circuit breaker anyway, it makes sense to build the protection directly into it. This type of breaker has a red light that indicates whether or not the surge arrester is functional. Once you install the device, whatever it is wired to will be automatically protected. Though the protection system is contained within the device for a particular circuit, the entire house will be protected—not just that circuit.
Providing surge protection directly at an electrical outlet is common practice because it is easy to do, you simply purchase the device and plug it in. No wiring needs to be done. This is called point-of-use protection. These types of surge protectors perform several layers of filtering to eliminate the noise on house wiring and prevent damage to highly sensitive circuitry. They are often used to protect personal computers and home audio-video equipent. Some point-of-use surge protectors electrically isolate their connected plug-ins so that the noise generated by a printer, for example, will not cross over to the computer. Be sure to buy a surge protector that has receptacles arranged in such a way that a plugged-in transformer will not block any of the unused outlets. Also look for one that provides telephone or modem protection.
Regardless of the quality of your surge protector, it cannot be effective unless it is connected to a good grounding system. An ideal grounding system will typically consist of one or more approved grounding rods and clamps. As a rule, the more grounding rods you have, the better the system. Be certain that the grounding wires are buried deeply enough not to be cut by your lawn mower or otherwise disconnected from the grounding system. Check local code for grounding wire depths.
A lightning strike produces a tremendous amount of power in the form of magnetic flux—lines of force moving through the atmosphere. These lines of force combine to induce a massive voltage and current pulse (fluctuation) in the utility lines. This pulse rides the line until it reaches and enters the electrical system within your home.Mounted in your main panel, a whole-house surge arrester acts to remove lightning pulses from the line, diverting them to the house grounding system (grounding rods), transforming large pulses into smaller, easily managed pulses. Point-of-use protection devices then carry off the smaller pulses and any others generated within a house that might be able to damage sensitive electronic equipment.