C7 Grounding & Bonding for Low Voltage Systems 4

Question 1

When installing a CCTV system on a metal building, the coaxial cable shield should be bonded to the building steel at which point?

Accepted Answer

At the point where the cable enters the building

Answer

NEC 820.93 requires coaxial cable shields to be bonded at the point of entry into the building to prevent lightning and fault currents from entering the system.

Question 2

Which conductor color is used for equipment grounding conductors in low voltage DC systems per NEC guidelines?

Accepted Answer

Green or bare

Answer

NEC 250.119 specifies that equipment grounding conductors must be green, green with yellow stripe, or bare copper.

Question 3

A low voltage technician discovers that two separate audio systems share the same ground bus but experience a hum. The MOST likely cause is:

Accepted Answer

A ground loop caused by multiple ground paths at different potentials

Answer

Ground loops occur when equipment is connected to ground at multiple points with differing potentials, inducing a hum voltage in signal cables.

Question 4

Per NEC Article 800, the protector for a communications circuit must be grounded to which of the following?

Accepted Answer

The grounding electrode system of the building

Answer

NEC 800.100 requires communications circuit protectors to be connected to the building's grounding electrode system using an acceptable grounding means.

Question 5

What is the maximum resistance typically acceptable for a telecommunications grounding electrode system (TGPE) per TIA-607?

Accepted Answer

5 ohms

Answer

TIA-607 recommends a TGPE resistance of 5 ohms or less to ensure effective fault current dissipation and signal integrity.

(C7) California C7 Low Voltage Systems Contractor Certification Practice Test

(C7) California C7 Low Voltage Systems Contractor Certification Practice Test

C7 Grounding & Bonding for Low Voltage Systems 4