Grounding and bonding

Grounding

10-112, Appendix B Material to ground conductors A grounding conductor shall be copper/alumnium/other accepted material and permittted to be insulated or bare.

10-114, Appendix B Grounding conductor Size for AC Systems shouldn't be smaller than No. 6 American Wire Gauge (AWG) of copper or No. 4 AWG of aluminium.

10-114, Appendix B Grounding conductor Size for AC Systems A grounding conductor can be smaller than prescribed in Subrule 1, but not smaller than the current--carrying conductor(s) of the grounded system.

Material for Bonding Conductors (1)

Bonding means fixed equipments shall be consist of one of these:

1. A great metallic interconnection between fixed equipments, with metal raceway, metal sheath, or cable armour except:

• • armour as specified in Subrules 2) and 3);

  • the sheath of mineral-insulated cable when not of copper

  • or aluminum, as specified in Subrule 4); or

  • where the raceway or cables are

    • run underground

    • run in locations coming within the scope of Section 22

    • or subject to corrosion

2. a bonding conductor run with circuit conductors part of a cable

3. or a bonding conductor with circuit conductors installed in raceways.

Material for Bonding Conductors (2,3)

Armour of armoured cables incorporating a bonding conductor shouldn't be seen to fulfill a bonding conductor's needs except if both the armour and bonding conductor are in continuous electrical contact. 

Unless marked, the armour of flexible metal conduit and liquid-tight flexible metal conduit should't be seen to meet a bonding conductor's needs and a bonding conductor shall be run in the conduit.

Bonding Conductor Size

The size of a field-installed bonding conductor put at other than service equipment shouldn't be less than the determined in accordance with Table 16 based on

a) the overcurrent device protecting the ungrounded conductors

b) the allowable ampacity of the biggest ungrounded conductor for installations where the size of the

circuit conductors is increased to compensate for voltage drop.

Often we use a copper bonding conductor with copper ungrounded conductors and aluminum bonding conductors with aluminum ungrounded conductors

Bonding conductor size example

What is the minimum size of copper bonding conductor for a circuit protected by 150 amp circuit breaker with conductors rated for 160 A?

A Safe Electrical System IV

Grounding Electrodes

1. Grounding electrodes shall have:

• • manufactured grounding electrodes;

  • field-assembled grounding electrodes; or

  • in-situ grounding electrodes forming part of existing infrastructure.

Grounding Electrodes

Building Conductors Older insulation is rated for 60 °C and is the lowest common temperature rating.

75°C insulation largely replaced 60°C conductors in the 70’s.

The current standard is 90°C.

If the temperature rate goes up, the conductors can carry more current without insulation failure.

Insulation temperature rating Higher temperature ratings are available for some

conductor types.

Conductor and cable types often include their temperature rating in their designation.

AC90 is an armored cable with 90°C insulation

Insulation

How does a wire “fail”? It's mostly the insulation failing.

The question is “How much heat can the insulation take?"

Conductor size

In a given set of conditions, a bigger wire can have more current

Tables 1 to 4: T1 & T3 are single conductors; T2 & T4 2/3

Single Copper 12 AWG R90 can carry 40 A

Single Copper 8 AWG R90 can carry 80 A

Single Aluminum 12 AWG R90 can carry 35 A

Single Copper 8 AWG R90 can carry 60 A

Installation method

How conductors are installed affects how well they can dissipate they make.

If heat isn’t dissipated, conductor temperature goes up.

Temperature is limited by limiting conductor current.

References

• [1] More from the CEC - Canva

• [2] 

Quizzes

• [Q1] Flashcard