Lightning protection

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 Question by Daniel Rodriguez posted 07 Jul 2005
 Lightning protection
Hi Joe, I am installing emergency phones in a 3 story parking garage. The emergency phones will be place inside the building, spread out over the various levels. Except for the last phone which will be placed on the top level of the
parking garage. The top level of the garage is exposed (exposed meaning does not have a roof). The voice cable will be install inside conduit which will be grounded with a meg bushing inside the garage telecom room. My concern is the last phone on the top level, do I need to provide some sort of lightning protection for that phone on the top level being that it is exposed or is it still within the buildings cone of protection. I appreciate your advice as always, Dan.
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 Answer by Joseph Golan posted 09 Jul 2005
Dear Daniel,

Lightning protection is a concern in any location where cables are exposed. You did not mention the source of the dial tone for these emergency phones, PBX or CO.

If the dial tone is being souced from a service providers Central Office (CO) then it is their responsibility for the protection (to protect their equipment). If this is a campus type installation and the dial tyone is from your PBX, then I would install lightning protection (Primary protectors) at the first point of entry to the building (Garage Telecom Room??) for ALL the active pairs, not just the one that is going to the roof.

Even though the cable may be run underground, it does not mean that it is not exposed to a potential lightning strike or crossing with a high voltage potential. Size the protector unit to the total number of the pairs that are entering the building (both ends of the cable) and then plug in the protector modules for the active pairs.

There are several manufacturers that make these units Commscope (formally Avaya), Siemon, Marconi, and I am sure there are others.

Again the protectors are to protect the user and equipment for a lightning strike getting to the cable. If you are concerned about a lightning strike hitting the actual telephone, that is a different story and other methods of lightning protection would be needing i.e. lighning rods or an elevation protector system. See an electrical engineer or a PE for more info on this.

Sincerely,
Joseph Golan, RCDD

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