Chapter 8 - Bonding and Grounding (Earthing)

Question 1

The equipment grounding (earthing) system is also known as the ____ in some countries.

Answer 1

Equipment bonding system

Question 2

The ac grounding (earthing) electrode system is also known as the ____ in some countries.

Answer 2

Earthing System

Question 3

The ICT designer must recognize that which three subsystems constituting the bonding and grounding (earthing) system should be placed at every site?

Answer 3

• ac grounding (earthing) electrode system
• equipment grounding (earthing) system
• telecommunications bonding infrastructure

Question 4

A standard Secondary Bonding Busbar (SBB) should have a minimum width of ____ and minimum depth of ____ with a variable length.

Answer 4

Minimum width of 2in

Minimum depth of 0.25in thick

Question 5

The ___ is a conductor that is intended to equalize potentials between TRs on the same floor of a structure.

Answer 5

BBC

Question 6

The Primary Bonding Busbar (PBB) must be bonded to what?

Answer 6

• Telecommunications Bonding Backbone (TBB)
• Equipment
• ac grounding (earthing) electrode system via the ac main service entrance panelboard and telecommunications bonding conductor (TBC)
• PBB can be bonded to several other telecommunications components

Question 7

The secondary bonding busbar (SBB) is bonded to what?

Answer 7

Either the telecommunications equipment ground terminal of the nearest ac electrical panelboard and building steel
or
the telecommunications bonding backbone (TBB)

Question 8

True or False

The telecommunications bonding backbone (TBB) is absolutely necessary.

Answer 8

False
The TBB is not an absolute necessity. As an alternative, the ICT designer can specify that the SBB in each TR be bonded to structural steel if present and to the nearest ac electrical panelboard. Each of the bonding connections should be tested to verify that a low-resistance connection exists.

Question 9

True or False
The backbone bonding conductor (BBC) is not needed if electrically continuous structural steel is bonded to the building’s grounding electrode system, and testing indicates this connection is sufficient to equalize potential across all telecommunications spaces.

Answer 9

True

Question 10

The primary bonding busbar (PBB) is minimum of ____ wide, and ___ deep.

Answer 10

4in W

0.25in depth

Question 11

The secondary bonding busbar is a minimum of ___ W and ___ depth.

Answer 11

2in W

0.25in depth

Question 12

The telecommunications bonding conductor (TBC) is at a minimum size of ___.

Answer 12

6 AWG.

The TBC at minimum is the same size as the largest telecommunications bonding backbone (TBB).

Question 13

The backbone bonding conductor should be installed where?

Answer 13

Every third floor for large systems.

Question 14

What is the recommended maximum ac current value on any bonding conductor?

Answer 14

Should be less than 1A, with a recommended max dc current value to be less than 500mA.

Question 15

The equipment grounding (earthing) system is the portion of the ac electrical distribution that serves what three purposes?

Answer 15

• It maintains 0V on all equipment enclosures during normal operations
• It acts as the intentional path for fault current under ground fault conditions
• Properly installed and maintained, it provides a voltage reference for end user telecommunications electronic equipment power supplies in order to stabilize bit pulses and steady state timing of internal circuitry

Question 16

The telecommunications equipment grounding (earthing) system impedance is dependent on what physical characteristics?

Answer 16

• Tightness of telecommunications equipment grounding conductor terminations
• Length of telecommunications equipment grounding conductor
• Number of bends in the telecommunications grounding conductor
• size of the telecommunications equipment grounding conductor
• radius of each bend in the telecommunications equipment grounding conductor path

Question 17

The impendence of the telecommunications equipment grounding conductor should be as low as possible, however what is the recommended max impedance value for ac circuits 120V to ground and 277V to ground?

Answer 17

1 ohm for 120V to ground
0.8 ohm for 277V to ground
If the impendence exceeds these max values, it can cause an electrical fault or end user telecommunications equipment may experience repeated malfunctions

Question 18

The telecommunications bonding conductor (TBC) should always be as short as practical and never be longer than ____.

Answer 18

30ft

Question 19

The telecommunications bonding conductor (TBC) is used to do what?

Answer 19

The TBC is intended to bond the Primary Bonding Busbar (PBB) to the ac grounding electrode system via the ac main service entrance panelboard.

Question 20

When testing the integrity of telecommunications bonding connections, a two-point bonding measurement should be performed. The recommended maximum value for the bonding resistance between these two points is ____.

Answer 20

0.1 ohms (100 milliohms)

Question 21

Interbuilding telecommunication cable runs of ___ or less, directly buried or in underground conduit is not considered to have lightning exposure. The shield or conduit must be bonded to the building’s ac grounding system at each end. This is a simplified zone of protection, as well as proper bonding practice.

Answer 21

140ft