GROUNDING AND SURGE PROTECTION RECOMMENDATIONS
A protection system with a poor ground is the same as having
no protection at all. Too many times proper grounding has been overlooked. Recommended
grounds are the utility company ground, a ground rod, well casings, and cold
water pipes that are of continuous metal. A note of caution, sometimes the metal-cold
water pipes are repaired and/or extended PVC piping. The introduction of PVC
material renders the cold water pipe ground “unacceptable”. A thorough
investigation of a cold water pipe ground is important since the PVC repairs
or extensions may be covered by drywall.
Grounds that are unacceptable include sprinkler pipes, PVC pipe, conduit, buried wire and any ground that cannot be verified.
Bonding ensures the most effective ground. Bonding ties all of the grounds in the building together electrically. If there is a rise in ground potential and all of the grounds are bonded, no damage will occur since it is differential voltage that causes problems.
It is absolutely necessary to make sure that the ground used for the AC power is the same as the ground used for the data-line surge protectors.
A common
ground reference must be achieved for all equipment. All ground wires must be
as short as possible and it is imperative that the ground wire not be coiled
nor looped. The ground wire must be as straight as possible, remember that it
must be the path of least impedance.
Regarding the diameter of the ground wire, the larger the better (NEC-250).
The larger the diameter, the better electrical conductivity. Finally, the earth
ground resistance on which the whole grounding system relies, must be less than
5 ohms.
Lines that typically need protection include incoming central office trunks, lines to off-premise sites, local area networks and campus environments with multiple buildings. A good rule of thumb to remember is that “all lines entering or exiting a building need protection”. Both ends of the cables between buildings must be protected.
David Pérez
Rolando
Electrical Engineer