Grounding, Bonding, and Electrical Protection Flashcards

What type of bonding conductor must be used to connect metallic cable tray sections together?

Answer: A jumper wire or splice plate listed for the purpose

Metallic cable tray sections must be bonded together using listed bonding jumpers or splice plates to ensure electrical continuity throughout the tray system.

In a telecommunications room, all metallic equipment racks should be:

Answer: Bonded to the TGB using appropriately sized bonding conductors

All metallic equipment racks in a telecommunications room must be individually bonded to the Telecommunications Grounding Busbar (TGB) to equalize ground potential.

What is the purpose of a protector 'heat coil' (also called a heat arrestor)?

Answer: To disconnect a cable pair when excessive current causes it to melt, preventing fire

A heat coil (heat arrestor) is a thermally-operated fusible element that disconnects a cable pair when prolonged overcurrent heats it past its melt point, preventing cable fires.

What is the recommended maximum length for a bonding conductor between a telecommunications rack and the TGB?

Answer: As short as practicable, typically not exceeding 4 m (13 ft)

ANSI/TIA-607 recommends bonding conductors be as short as practicable, and practical guidelines suggest keeping rack-to-TGB runs within 4 meters to minimize impedance.

Why is it important to isolate the telecommunications grounding system from the AC power grounding system except at the single interconnection point?

Answer: To prevent noise currents from AC power circuits from circulating in the telecommunications ground path

Isolating the telecommunications ground except at one interconnection point prevents AC power noise currents from circulating through sensitive telecom equipment grounds.

A telecommunications system designer is reviewing a building's grounding system and finds that the building uses a Ufer ground (concrete-encased electrode). What advantage does this provide?

Answer: Ufer grounds offer very low impedance due to the large concrete mass in contact with earth

Concrete-encased electrodes (Ufer grounds) leverage the large mass of reinforced concrete in contact with soil to achieve very low grounding impedance, benefiting the entire bonding system.