This article will go over the key concepts and application pertaining to grounding and bonding as it relates to the Canadian Electrical Code. The Canadian code differs slightly in the area of grounding on bonding in comparisons with America’s National Electrical Code, so please be aware of this when reading this article.

Why grounded circuits?

There are three main reasons for grounding our AC systems:

  1. Safety. Grounding the systems provides a a low impedance path for fault current to return back to the source.
  2. Establishes a voltage reference point. In a grounded system, the ground point establishes the 0V reference point and all other voltages are with reference to this 0V level. For example when we say 120V, we are actually stating 120V with respect to ground.
  3. Keeps non-current carrying metallic parts at an potential to ground.
The Four Main Component

Per the Canadian Electrical Code, we have the four main components in a grounded system:

  1. Grounding electrode
  2. Grounding conductor
  3. Grounded conductor
  4. Bonding conductor

A-3ph

Component 1: Grounding Electrode

b_3p

Definition in the CEC: a buried metal water-piping system or metal object or device buried in, or driven into, the ground to which a grounding conductor is electrically and mechanically connected

Examples of grounding electrodes: ground rod, ground plate, metallic water piping, etc.

Watermain used a grounding electrode, the green wire in the photo is the grounded conductor:

dsc_1694b

lightning-grounding-clamp-tyco

 

Component 2: Grounding Conductor

c_3p

Definition in the CEC: a buried metal water-piping system or metal object or device buried in, or driven into, the ground to which a grounding conductor is electrically and mechanically connected

CEC Rule 10-806(1) Excerpt: “the grounding conductor for a system shall be without joint or splice throughout its length, except in the case of busbars, thermit-welded joints, compression connectors…”

In the previous photos showing the grounding electrodes, the wire going to the electrode (the green one for the water line, and the bare one for the ground rod) are the grounding conductors. As per the diagram, there should be only a single grounding conductor going to the grounding electrode.

Component 3: Grounded Conductor (Neutral)

d_3p

CEC Rule 10-210 states that in AC systems (3 phase 4 wire) the grounded conductor is the identified neutral conductor.

CEC Rule 10-204 Excerpt: “…the system shall be connected to a grounding conductor at each individual service, with the connection made on the supply side of the service disconnecting means either in the service box or in other service equipment; and except as provided for in Rule 10-208, have no connection between the grounded circuit conductor on the load side of the service disconnecting means and the grounding electrode”

This rule is basically telling us there is only one point where the grounded conductor (neutral) and your grounding conductor ( the conductor going to the grounding electrode) are to be connected. This is the reason why in a main panel or switchboard we are required to connect the ground bus and neutral bus, but in sub panels and every where else down stream on the load side we have to ensure the ground bus and neutral bus are separate.

Here is an example of a main panelboard, where the neutral bus and ground bus are connected:

groundneutralconnect

 

Here is an example of a panel on the load side of the service disconnecting means (i.e. a sub panel) with the ground bus and neutral bus separated (no connection allowed between the two):

groundneutralbus

You must be extra diligent not to connect ground and neutral in a sub panel. Some sub panels come with grounding screws that allow provide a connection between the neutral bus and ground. Even if you do not have a grounding screw/strap, an adequately sized wire connection between the ground bus and negative bus will do. If however you are using the panel as a sub panel, you must remove the grounding screw and ensure no connections are present between ground and neutral.

Here are photos showing the grounding screw in the neutral “cross-arm”:

groundscrew

Here is a slightly panelboard with a slightly different method allowing for a connection between the neutral bus and ground with a swivel type strap.

2QEZSNeutral and ground connected
OX2O1Neutral and ground seperate
Component 4: Bonding Conductor

e_3p

Definition in the CEC: “a conductor that connects the non-current-carrying parts of electrical equipment, raceways, or enclosures to the service equipment or system grounding conductor”

By this definition, we understand that under normal operating conditions there should zero current on the bonding conductor. The only time the bonding conductor should be carrying current is if there is a ground fault in the system. This is why we never connect the bonding conductor to neutral. The neutral conductor (grounded conductor) is a normal return path for the line current. If we make a connection between the bonding conductor and neutral, it is possible to have the situation in which the neutral return current can opt to return to the source on the bonding conductor instead of the neutral conductor. This is what is known as creating a ground loop. All though both the bonding conductor and the neutral conductor eventually end up connecting to the grounding electrode, we must distinguish the two.

Here is an example of the bonding conductor (the one in green) for a receptacle:

20067-68(copy)

Here is an example of where the conduit (raceways) are connected to the bonding conductor by means of a special connector used at the end of the conduits:

4_BondingBushing

NO COMMENTS

Leave a Reply