[petestoddard]

I am installing a 300-pair unlisted (OSP)communications cable between 2 buildings. I intend to bury 4" Schedule 40 PVC conduit in a trench between the buildings. In one of the buildings I have to run the cable about 200 feet through a crawl space to the telecom room. The customer does want a splice case in the crawl space and is willing to pay for conduit. I have been told that the unlisted cable can be intalled inside the building for more than 50 feet as long as it is in conduit. I have 2 questions, 1) is that information correct? 2) If so does the conduit have to be EMT or would PVC be acceptable?

[tkrussell]

See Section 800.48 of the 2008 edition of the National Electric Code that I believe addresses your question:

800.48 Unlisted Cables Entering Buildings.
Unlisted outside plant communications cables shall be permitted to be installed in locations as described in 800.154(C) where the length of the cable within the building, measured from its point of entrance, does not exceed 15 m (50 ft) and the cable enters the building from the outside and is terminated in an enclosure or on a listed primary protector.

FPN No. 1: Splice cases or terminal boxes, both metallic
and plastic types, are typically used as enclosures for splicing
or terminating telephone cables.
FPN No. 2: This section limits the length of unlisted outside
plant cable to 15 m (50 ft), while 800.90(B) requires
that the primary protector be located as close as practicable
to the point at which the cable enters the building. Therefore,
in installations requiring a primary protector, the outside
plant cable may not be permitted to extend 15 m (50 ft)
into the building if it is practicable to place the primary
protector closer than 15 m (50 ft) to the entrance point.

The NEC can be reviewed on line at NFPA.

Does not appear conduit is required, provided the cable is protected properly.

If conduit is needed, whether EMT or PVC is needed will depend on the fire rating of the building.