Free RCDD sample questions

Correct answer: 10 bundles

This question requires a calculation based on the cross-sectional area of the cables and the conduit. A 76mm (3-inch) conduit has a total internal area of approximately 4768 mm². The 40% fill area is 1907 mm². The approximate area of a Cat 6A cable is 55 mm² and an OM4 duplex cable is 25 mm². A bundle (2x Cat 6A + 1x OM4) has an area of (2 * 55) + 25 = 135 mm². Dividing the available fill area by the bundle area (1907 / 135) gives approximately 14.12. However, due to cable packing inefficiency (nesting), a derating factor must be applied. A more realistic calculation using cable packing formulas or standard tables indicates that approximately 10-11 such bundles can fit. Of the choices given, 10 is the most realistic and safe answer.

Correct answer: Utilizing the building's structural steel as the primary TBB, with short bonding jumpers from each TGB to the nearest column.

TIA-607-D recognizes that for high-rise buildings, using the structural steel framework as the TBB provides the most effective equipotential plane, especially for high-frequency events. This method minimizes the length of bonding conductors from the TGBs to the backbone, reducing impedance. A daisy-chained conductor (A) is explicitly not permitted. A looped conductor (C) can create unintended current paths. Home-running each TGB (B) is compliant but can be extremely expensive and less effective at high frequencies than using the massive conductive grid provided by the building steel.

Correct answers: F/UTP (Foiled/Unshielded Twisted Pair); S/FTP (Shielded/Foiled Twisted Pair)

F/UTP cable includes an overall foil shield around all four pairs, which provides good protection against external EMI.

S/FTP provides the highest level of EMI protection by combining an overall braid shield (S) with individual foil shields on each pair (FTP).

Correct answer: True

The TDMM recommends that telecommunications spaces be treated as finished rooms. This includes painting the walls, sealing the concrete floor, and installing the final floor finish (e.g., static-dissipative tile) before heavy equipment like racks and cabinets are brought in. This practice minimizes dust and debris that could harm sensitive electronic equipment.

Correct answer: Reject the results for the affected links and request the contractor investigate and remediate the cause of the low headroom.

While a 'Pass' is technically compliant, extremely low headroom (e.g., less than 1-2 dB) indicates a marginal installation that may be susceptible to performance degradation over time due to environmental changes or minor disturbances. It often points to poor termination practices, tight bend radii near the connector, or non-compliant components. Best practice is to investigate and remediate these marginal links to ensure long-term system reliability and performance, rather than just accepting a bare-minimum pass.

Correct answer: A ladder rack or basket tray system suspended above the primary lab area.

For open-ceiling environments requiring high flexibility, a cable tray system (ladder rack or basket tray) is the ideal solution. It provides continuous support, simplifies adding, moving, or changing cables (MAC work), and can handle high cable densities. Conduit systems are inflexible, and while J-hooks offer some flexibility, they don't provide the continuous support or capacity of a tray system, which is crucial in a large, dynamic lab space.

Correct answer: removed

Both the National Electrical Code (NEC Article 800.25) and TIA standards mandate the removal of abandoned communications cables. These cables, which are not terminated at both ends and not identified for future use, increase fire load in plenum and riser spaces and can restrict airflow, posing a significant safety hazard.

Correct answer: OS2 Singlemode

According to the IEEE 802.3 standards, 40GBASE-SR4 has a maximum channel length of 100 meters on OM3 and 150 meters on OM4/OM5 fiber. Since the required distance is 280 meters, none of the multimode options are sufficient. The RCDD must specify a singlemode fiber solution, such as 40GBASE-LR4 over OS2 fiber, which can reach up to 10 kilometers.

Correct answers: Installing a specific, tested, and listed firestop system appropriate for the wall construction, penetrating item, and annular space.; Ensuring the depth of the firestop sealant meets the minimum specified in the listed system.; Applying a fire-rated label to the sleeve after installation.

Compliance requires using a complete engineered system (e.g., from UL or Intertek) that has been tested for the specific conditions, not just a recognized product.

The thickness of the sealant is a critical component of the system's fire rating and must be installed as per the system's instructions.

Properly identifying the firestop penetration with a durable, code-compliant label is required for inspection and future maintenance.

Correct answer: Run two separate backbone cables to each IDF. Route the primary cable for all IDFs through one riser shaft and the secondary (redundant) cable for all IDFs through the second, physically separate riser shaft.

This design achieves true pathway diversity. By routing the primary and secondary backbone cables through two physically separate and fire-rated riser shafts, it protects against a single catastrophic event in one shaft taking down all connectivity. A single point of failure in one pathway is completely mitigated, meeting the client's high-availability requirements. The other options introduce single points of failure at the pathway level.