We all know the value of grounding and bonding for electrical systems and for telecommunications equipment. Ensuring safety is the top priority, followed by minimizing damage. Why might more protection be considered? We are in a high-technology era where "communications" have now become a necessity for business and for the contemporary home.
"Protection" will only be effective in a properly grounded electrical environment. Minimum requirements are described in NEC Article 250. Proper grounding and bonding have been inconsistently defined throughout the United States, because weather and geologic conditions affect protection needs for communications.
Grounding and bonding have many purposes in electrical and telecommunications installations, including:
- limiting potential differences between conductive structures caused by electrical disturbances such as power faults, lightning strikes, electrostatic discharges, or voltage differences;
- providing planned paths with sufficient capacity to carry currents away from operating equipment;
- providing immunity to noise and electromagnetic interference to the telecommunications installation; and
- contributing to reliable equipment operation.
A designer can recommend types of available primary protection for outside the building where the neutral and ground conductors are bonded. A gas tube surge arrestor offers protection after it is installed at the demarcation point inside the building, where the telephone company's responsibility for it ends. Better technology protection is available that is not required by the telephone company. It can be either incorporated into the equipment or installed as part of the overall system, in accordance with the manufacturer's recommendations and based on local conditions.
Insurance companies, electrical architects, network engineers, and the end user determine the necessity of protection. With utility deregulation, companies may recommend ways to use protection-which they, of course, provide.
Equipment design provides protection
A designer needs to define the equipment's grounding, bonding, and protection requirements-for all environments in which the equipment is to be installed. This thoroughness is what distinguishes the solid, knowledgeable, caring suppliers from all others.
Studies have shown that about 80 percent of all disturbances on data lines are generated internally (by elevators, HVAC, etc.). These internal disturbances obviously occur more frequently than other types. The other leading disturbances stem from faulty data routing. This leads to coupling (the unwanted transfer of power from one circuit/system to another). Properly designed wiring minimizes internal disturbances; wise data routing minimizes coupling.
Monitoring protection needs
The network engineer should be involved with the original design team and at the start of a new installation. Ideally, the engineer provides all the electrical requirements for equipment to be used. The design team should review the grounding and bonding that is going on-determining requirements for the grounding grid for each floor.
There are general grounding requirements for a telecommunications room. The system designer looks at the equipment grounding and designs the tray system that carries the cable. This is where the communications cable can be isolated from the electrical cabling. After the tray design is completed, the request for proposal goes out to the cable vendor, who is required to install systems that are compliant with TIA-606 (Administration Standard for the Telecommunication Infrastructure of Commercial Buildings) and TIA-607 (Commercial Building Grounding and Bonding Requirements for Telecommunications). These requirements are separate from the electrical system.
The final task is designing the racks and cabinets, which all need to be bonded to the grounding system. The company pre-runs the green wires, which are to be grounded, in the room. That way, when racks or cabinets come in, this green wire is already there to attach to that new cabinet. (The only drawback is if the design is changed, a new green wire has to be brought in to the cabinet.)
Ideally, after installation, the company has monthly walk-throughs/inspections to ensure that inadequate power strips are not being used with too many servers, or that cabinets are not plugged into wall outlets (that could easily be unplugged by a janitor). Either situation could put the system "down." The monthly inspection is done to prevent the servers from crashing. If an inspection revealed that four new cabinets were suddenly installed in a room, the inspector would check to see if they were grounded, that the power was properly used, and that the circuit could adequately handle them.
Employees should not be using power protection at their desks. Protection should always be centered in the server room and main telecommunications room. An uninterruptible power supply (UPS) should be provided in the server room only. Using protection at a desk seems pointless because in a power outage to the building, the server in the closet would be out and users wouldn't be able to access the corporate network anyway. The user with protection at the desk might still be able to play cards on that desktop unit, but couldn't work on the network.
Electrical contractors should follow these steps for protecting a commercial building.
- See what the system is specified to handle and determine if it is adequate.
- Find out what the geographic exposure is (e.g., Florida has more lightning exposure than a western state might).
- Note the history of outages in the area. History will tell you what to expect.
- Ask if there have been any "shut downs" in the area.
- Inspect the electrical system coming in.
- See that the telecommunications infrastructure is bonded to the same ground as the electrical-to eliminate potential voltage differences.
- Check with the telephone or power companies for their recommendations.
The contractor should look at slightly different things when working with a system for a residence.
- First, recognize that the homeowner is responsible for determining the level of protection needed.
- Review the geographical exposure.
- Check out the grounding system and understand it well enough to explain it to the owner, who is ultimately responsible.
- Discuss the telecommunications needs by contacting the appropriate telephone company engineers.
Review all the equipment in use and its exposure, especially if this involves a home office. A full review of possible future upgrades should also be made. Remember-the risk to a small business is far too serious to neglect.
When purchasing a commercial protector, be sure it's listed to Underwriters Laboratories (UL) 1449, Revision 2. This means the equipment has passed the latest tests devised by UL for safety. The application guidelines are explained in IEEE C62.41-1991, titled "IEEE Recommended Practices on Surge Voltages in Low-Voltage AC Power Circuits."
To do a thorough job, one corporate telecommunications engineer suggests questioning relentlessly to ascertain as many requirements as possible before designing a system. Include what's effective for your customer. Then follow up with a monthly inspection to verify systems are still protected. It's easy to see whether any new unprotected systems have been installed. If people change jobs, you also need to keep current; this is where documentation is essential.
A major equipment manufacturer recommends getting the developer, builder, engineer, and service provider together early on, specifically to discuss the grounding and protection needs for the building. That firm believes this ensures the best design with a minimum of future changes.
A major designer and manufacturer of radio frequency (RF) protection devices and grounding solutions for the telecommunications industry recommends taking the "applications" approach. Ask your service provider what protection is being furnished with their equipment and if it is the homeowner's or business's responsibility to provide it. The user should speak directly with engineers about liabilities.
MICHELSON, co-publisher and editor of the Cabling Standards UPDATE (a quarterly report dedicated to informing about standards revisions focusing on cabling), can be reached at BCS (800) 492-8422; fax: (925) 846-9901. Her Web site address is www.cabingstandards.com.