NEC 800.90 requires protective devices on both ends of outside communications cables. We are adding a portable classroom to an existing school and running a non-shielded OSP telephone cable underground in PVC conduit from the building housing the phone equipment to the portable classroom which will have one telephone. One primary protector exists for the incomming overhead telephone service from the phone company. Over the years, a multipurpose building and many portable classrooms have been added to the site and none of the outside phone cables have protectors.
Exceptions (1) and (2) definitely do not apply to our installation. Exception (3), maybe. If the area has an average of five or fewer thunderstorm days per year and earth resistivity is less than 100 ohm-meters, we do not need protectors. Where do we go to find such information???
Exceptions (1) and (2) definitely do not apply to our installation. Exception (3), maybe. If the area has an average of five or fewer thunderstorm days per year and earth resistivity is less than 100 ohm-meters, we do not need protectors. Where do we go to find such information???