A few thousand dollars invested in a grounding system upgrade protects $1.5 million in communications and computing equipment. No region of North America receives more lightning strikes than central Florida. With more than 100 days of severe thunderstorms every year, the area from Jacksonville to Tampa is justifiably known as the lightning capital of the world. You don't want to be caught on the golf
No region of North America receives more lightning strikes than central Florida. With more than 100 days of severe thunderstorms every year, the area from Jacksonville to Tampa is justifiably known as the lightning capital of the world. You don't want to be caught on the golf course swinging your 9-iron when one of those electrical storms comes rumbling by. And it can be a tough place to operate a business — especially one that relies on sensitive electronic equipment. That is, unless you've invested in adequate lightning and surge protection equipment and a reliable low-resistance, low-impedance grounding system.
With resorts in Kissimmee, Miami, Lake Buena Vista, and Palm Coast, Clarion World Resort hosts thousands of Florida vacationers every year, requiring state-of-the-art, computerized business systems for reservations and time-share information, which must operate smoothly and reliably. In recent years, it has become even more important for the condominium operator to ensure uninterruptible telephone service to its guests, many of whom are elderly. What use is a 9-1-1 emergency system if lightning knocks out the phone system?
The big one hits Kissimmee.
That's just what happened at the Resort World facility on June 1, 1998. A massive, nearby lightning strike and the resulting power surge took out not only the facility's $160,000 telephone switch and phone system, but also an assortment of computers, 60 TV sets, and 30 microwave ovens. Despite the damage, no one was hurt. However, the telecommunications system and other sensitive electronics were destroyed.
The resort had up to that point enjoyed a false sense of security because although the grounding system installed in the mid-'80s met the national and local electrical codes at the time, its communications infrastructure had been upgraded continuously and had grown much more sophisticated. As a result, the old grounding and surge protection system was no longer capable of protecting the new equipment (Photo 2 right). In fact, the company's insurance carrier took one look at the grounding and surge protection systems and refused to continue coverage unless they were upgraded.
Lightning specialist finds poor-quality grounding.
At this point, Clarion turned to Power & Systems Innovations, Inc. (PSI), a 12-year-old Orlando-based electrical consulting and design company that specializes in lightning protection and related power quality issues, for help.
John West, PSI's founder and president, assessed the site and confirmed what the resort and insurance carrier knew to be the source of the problem: inadequate grounding and surge protection. He first noted that the communications and computer offices were grounded through four original 10-ft galvanized steel grounding rods. The rods were connected with 2 AWG copper wire using screw-type connectors, with a single 2 AWG lead to the meter box. From there, he noted, they ran to an interior panel. West also noted the feeder cables were aluminum. Mechanical connections at the ground rods showed some corrosion, which can occur at the connection point of dissimilar metals. West also believed that the surge protection arrangement wasn't adequate considering the expensive equipment in use. Everything he found had been installed according to Code, but this work was done years before the electronics had been upgraded. He measured the ground resistance of the system using a fall-of-potential meter, gathering a reading of 105 ohms. Though it was high, it wasn't unusual in that part of Florida, despite the area's high water table.
The NEC allows for a maximum resistance of 25 ohms at the grounding electrode (250.56). West, however, adheres to much tougher specifications for the systems he designs. His specs permit a maximum of 5 ohms at the electrode system — no matter how many electrodes are installed for a given structure. For the electrode located at the service entrance, he insists the resistance be measured in the standalone condition with the system disconnected from the utility neutral. He also insists that the contractor document the fall-of-potential test technique he used along with the type of instrumentation and its most recent date of calibration. After the installation is complete, he calls for a second documented ground resistance test of the entire grounding system. His company will also conduct its own follow-up tests, just to make sure the readings are lower than 5 ohms.
To improve the grounding system at the facility, West installed six 50-ft, ¾-in. diameter copper-clad rods in a row running parallel to the rear of the resort's communications and computer offices, about 12 ft from the structure. He had to go down 50 ft to get below 5 ohms. He then connected the electrodes using 4/0 AWG stranded copper cable, exothermally bonding every joint. He also bonded to the fence surrounding an existing on-site generator and tagged onto the existing electrodes (Photo 3 above). When he was finished, the resistance readings had dropped to less than 4 ohms.
PSI then ran a 4/0 copper ring — also known as a halo ground — into and around the inside of the Resort World offices, running the cable along the walls, about 6 ft up. They bonded the 4/0 copper from the halo to the neutral-ground connection at the service entrance by way of copper ground plates mounted on the wall and lengths of 29X copper lightning cable. The ground plates were connected with 4/0 copper, and connected to smaller tinned-copper bus strips from there to panels serving the MIS equipment, as well as the equipment itself, using 4 AWG copper. All turns in the grounding cables are generous — the specs call for sweep bends with a 4-in radius, minimum. No sharp, 90° bends were permitted. The result? The resort hasn't lost or suffered damage to any equipment since the installation of the new grounding system.
But what about the cost?
Proper grounding doesn't have to be expensive — and in this case it wasn't. The $3,500 upgrade to the low-resistance grounding system at Resort World protects more than $1.5 million of equipment — relatively inexpensive insurance. Not only that, the resort's patrons can count on the phone system working, regardless of the weather.
Padgett is director of communications for Clarion Resort World, Kissimmee, Fla. West, Sr., is president of Power & Systems Innovations, Inc. (PSI), Orlando. David Brender of the Copper Development Association also contributed to the development of this article.