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SECTION 2 - GROUNDING ELECTRODES

All parts of the grounding and bonding system can be controlled by careful design and material selection, except for the system’s actual connection to the earth. The quality and reliability of this connection depend on the resistance of the earth on which the building stands, on the moisture content of the earth and on the grounding electrode or electrodes that are placed in the earth, which are all variable factors. For this reason, installers must determine the best possible electrode system that is consistent with the requirements of a given electrical installation.

A grounding electrode is a buried metal water-piping system or a metal object or device buried in, or driven into, the ground that makes intimate contact with the earth, to which a grounding conductor is electrically and mechanically connected.

Subrule (1) of rule 10-700 of the CEC recognizes three kinds of grounding electrode:

(a)

those manufactured in a factory setting and approved in accordance with CSA C22.2 No. 41, such as rod and plate electrodes.
(b)

those manufactured on-site using bare copper conductors directly buried or encased in concrete (field assembled grounding electrodes);
(c)

a grounding medium that is already present in the building infrastructure such as a water piping system, a well casing, etc. (in-situ grounding electrodes).

ROD ELECTRODES:

Two manufactured rod electrodes must be installed. Each rod must be at least 3 m long as required by CSA C22.2 No. 41. Each rod must be driven into the earth to its full length, spaced no less than 3 m apart and bonded together by a copper grounding conductor.


PLATE ELECTRODES:

Plate electrodes must:

(a)

have an exterior surface area at least 0.2 m sq. (as required by CSA C 22.2 No. 41) in contact with the soil and be buried at a depth not less than 600 mm below finished ground level;
(b)

be encased within the bottom 50 mm of a concrete foundation footing, in direct contact with the earth and not less than 600 mm below finished grade.

(2)

 in multi- phase systems in which one phase is used as a single-phase 3-wire system, only one phase shall be grounded.

BUILDING INFRASTRUCTURE:

The CEC addresses in-situ grounding electrodes provided by building infrastructure such as a water piping system or a well casing. Such electrodes must be 600 mm or more below finished grade and have a surface area equal to a manufactured grounding electrode,

For example, an underground metal water piping system located at least 600 mm below finished grade and extending at least 3 m has traditionally been recognized as a suitable grounding electrode. The metal reinforcement of concrete slabs, concrete piling and concrete foundations as well as iron pilings, when they are in significant contact with earth 600 mm or more below finished grade, have also been found to be suitable in-situ grounding electrodes.

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