What are the different standards for phone & data-line surge suppression?
• UL 497 Primary Protectors: According to NEC, primary protection systems must be listed for the
purpose and located as close as possible to the building entry point on exposed telephone circuit. Exposed
circuits are telephone company cables that enter the building from the outside world. The listing requirement is UL 497 for all primary protection systems.
• UL 497A Secondary Protectors: A secondary protection system must be listed for and be installed in series between the primary protector and the protected equipment. All secondary protector systems must safely limit overcurrents to less than the current carrying capacity of the telephone cab les and equipment. The listing requirement is UL 497A for all secondary protection systems
• UL 497B Isolated Loop Protectors: This requirement covers protectors for isolated loops or lines that are contained within a building and not connected to the public network outside the building. These devices protect against transients usually caused by electrostatic discharge and electrical shock.
My telephone company tells me they have surge suppression equipment installed. This means I don't need anything else, right?
Telephone access is provided by your local provider from the Central Office. The cable is taken to the individual building and is cut off at what is referred to as the " Telco Demarcation Point". At this point, the telephone company provides primary protection. They do so because they have to meet code – NEC Article 800 states that you must have a list primary protector on all lines at the building entrance and no more than 50 feet (and they are responsible for that). They are not concerned about the equipment within the building, but rather to meet code requirements. Most commonly, they use "5-pin gas tube arresters". This technology was fine when phones were more robust...but today's electronics don't allow much room for error.
Stedi-Power, Inc. sources equipment that provides the maximum protection for your equipment.
How do I determine where to put suppressors? Do I need to cover every single phone and fax line?
This can be very complicated and take a great deal of time and effort. Basically, you want to provide "just enough" protection. "Too much" protection can make troubleshooting problems difficul t...even when it is logically the best approach. The following diagram shows the relationship between the different Code requirements and UL Standards. The locations marked with red boxes (white lettering) are the minimum suggested requirements for lightning protection. A distinct possibility exists that internal equipment can still be damaged through induction in the event of a power outage or lightning strike if minimal protection is chosen:
|UL 497||Trunk Primary|
|UL 497A||Trunk Secondary|
|UL 497A||Station Secondary|
|UL 497||Station Primary|
|UL 497B||Isolated Loops|
|Power Line (Service Entrance...should qualify as surge arrester) *see note|
|UL 1449||Power Line (Sub-distribution panels...surge suppressor is sufficient) *see note|
|Note: Surge suppressors must be rated as surge arresters to be properly sited at these locations. Stedi-Power, Inc., also suggests that all panels that service outside equipment be treated as if it were a "service entrance"...and recommends surge arrester-rated devices on these panels.|
|ALL Equipment manufactured by Stedi-Power, Inc. is rated as both a surge arrester and a surge suppressor.|
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Last Updated: 07 Jun 2004
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