NEC770-50

[yaqn]

NEC 770-50
Exception No. 1: Optical fiber cables shall not be required to be listed and marked where the length of the cable within the building, measured from its point of entrance, does not exceed 50 ft (15.2 m) and the cable enters the building from the outside and is terminated in an enclosure.?

1)The 50 ft (15.2m) mentioned above, is it a linear distance ? and how it is measured ?
2) A non listed fiber optic cable enter a building through a cable vault below the building. A slack of 30 m was left in the cable vault and then the cable run through a sleeve in the ceiling of the cable vault, to the patch panel. The length of the FOC from the slack point to the termination point is 16m.(total length of the FOC from the entrance point to termination point is approx. 157 ft ). So is the installation consider in conformance with the NEC requirement or not?

 

[gregory]

Re: NEC770-50

NEC 770-50 exception 1 says that the cable length shall not be more than 50 feet long inside the building. The valt is considered outside the building. you would measure the cable length along the cable from where it enters the building from the vault. the cable in the vault and what is coiled up does not count. if there is more than 50 feet of fiber optical cable in the building & it is not listed & marked, it is a violation. I am impressed that you noticed and are aware of this code!

 

[yaqn]

Re: NEC770-50

Gregry, thanks for your reply. However, the cable vault is 8ft x 24 ft and it is below the building in which the MDF is above it directly. So why it is consider not part of the building ? Also, the cable vault access is near the MDF (square metallic cover with hinges). In addition, the air ventilation to the CV provided through the main AC ducting for the central office building. So, is the installation still meets NEC770-50 or not ?