RCDD Question #255: Real Exam Question with Answer & Explanation

The correct answer is C. 209 m (686 ft). Per NEC Section 800.154, unlisted outside plant (OSP) communications cable may extend a maximum of 15 m (50 ft) inside a building beyond the point of entry before it must be terminated or transitioned to a listed (plenum, riser, or general-purpose) cable. Because the conduit conn

Question

You are placing an entrance cable between two buildings connected by a conduit 205.3 m (588 ft) in length. What would be the MAXIMUM length of unlisted OSP cable that could be used before you terminate the cable or transition it to a listed cable?

Options

A185 m (607 ft)
B200 m (656 ft)
C209 m (686 ft)
D213 m (700 ft)
E216 m (708 ft)

Explanation

Per NEC Section 800.154, unlisted outside plant (OSP) communications cable may extend a maximum of 15 m (50 ft) inside a building beyond the point of entry before it must be terminated or transitioned to a listed (plenum, riser, or general-purpose) cable. Because the conduit connects TWO buildings, the cable enters and exits at both ends - so you add one 15 m (50 ft) indoor allowance for each building: 179 m (588 ft) conduit + 15 m (50 ft) at Building 1 + 15 m (50 ft) at Building 2 = 209 m (686 ft) total. Note: the metric value shown for the conduit length in the question (205.3 m) appears to be a typographical error; the operative figure is 588 ft (≈179 m).

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