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Grounding
Tips
How
To Take Care of This Incredibly Important Variable
by
Gregory Hayward and Mohammad Masghati, ITW Linx. As printed in
Teleconnect Magazine, January, 1992.
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| Needless
to say, you must select the proper equipment to protect your sensitive
phone/computer CPE. But that's just part of the power-protection battle.
Once the proper protector has been
chosen, the next step is making sure everything is grounded correctly.
The following items are critical to obtaining an optimum grounding
system.
1. Bonding. Bond or electrically
connect together at a single point all of the grounds used for
protectors an communications equipment. Typical grounds used for
protectors are metal water pipes, ground rods, well casings, chemical
rods, etc. The communications equipment is typically connected to the
power company's multi-grounded neutral (MGN) system and is the best
source for a single-point ground. Connect the protector (primary and
secondary) and cable shield grounds to the equipment grounds (i.e.
multi-grounded neutral) with a six AWG solid copper bonding wire (see
chart).
2. Physical Connections. Make sure
to use the recommended ground wire size and UL Listed ground wire
connections (again, see chart). For ground wire over 60 feet in length,
the next largest wire gauge should be installed. Use a large radius at
each bend in the ground wire. DON'T coil ground wire under any
circumstances. Coiled wire can act as an inductor that dramatically
increases the resistance of the path to ground, jepardizing the
effectiveness of overvoltage devices. |
3.
Check Ground System Impedance. There are numerous brands of
equipment and methods for checking the integrity of a grounding system.
Pick one that tests both continuity and the impedance (total resistance)
with respect to a true ground. An ideal ground should have an impedance
under .250 ohms.
4. Cable Shields. The metal cable
shield should be bonded to the protector/ground systems on both ends of
the cable.
5. Unused Cable Pairs. They must
be grounded on the unprotected side of the protector.
6. Campus Building. Treat each
building independently. Do all of these instructions in each building.
Is grounding important? You bet your
sweet voltage surge it is! The effectiveness of all overvoltage
protectors relies on a path of least resistance for "dumping"
transient voltages. The higher the resistance to ground, the higher the
true activation level is for a protector ( and the lower the activation
level, the better.)
Please don't forget about grounding. Time
spent on grounding basics may mean the difference between big downtime
costs and an excellent return on your investment. |
