|  | 8.11 |

Network Power Supply Issues: Surge Suppressors and Uninterruptible Power Supply (UPS) Functions

| 8.11.1 | Surge suppressors: networking device locations

Surge suppressors are usually mounted on a wall power socket, to which a networking device is connected. This type of surge suppressor has circuitry that is designed to prevent surges and spikes from damaging the networking device. A device called a metal oxide varistor (MOV) is most often used as this type of surge suppressor. An MOV protects the networking devices by redirecting excess voltages, that occur during spikes and surges, to a ground. Simply put, a varistor is a device that is capable of absorbing very large currents without damage. An MOV can hold voltage surges on a 120 V circuit to a level of approximately 330 V.

Unfortunately, an MOV may not be an effective means of protecting the networking device that is attached to it. This is because the ground also serves as the common reference point for data signals going into and out of the computer. Dumping excess voltages into the power line near the computer can create problems. While this type of voltage diversion can avoid damage to the power supply, it can still result in garbled data.

When surge suppressors that are located in close proximity to networking devices divert large voltages onto the common ground, this can create a large voltage differential between network devices. As a result, these devices can experience loss of data, or in some instances damaged circuits.

You should also be aware that this type of surge suppressor has a limited lifetime, dependent, in part, on heat and usage. For all of these reasons, this type of surge suppressor would not be the best choice for your network.