Title: Module 6: Grounding and Bonding
Course: Basic Electrical Theory and Wiring (Sandbox) > Section: Module 6: Grounding

Introduction

Electricity needs a path to flow, just like water. If you cap the end of a hose, the flow stops. If you open the cap, water can continue to flow.

Electricity does not flow through air very well. Therefore, electricity needs a connection in order to flow. Electricity wants to flow back to the earth, regardless of the path. If you touch a wire and you are touching the earth, the electricity will flow through you to get to the earth. Grounding does a couple of things:

1. It provides a safe path for the electricity to flow in case there is a failure in the wiring or component.
2. It gives electricity a point of reference.

Importance of Grounding

How does electricity provide a point of reference? Well, having things grounded at different points can actually create different potentials. For example, let's say I have a live 480 V wire at a factory 2 miles away. If I touch that wire, my reference to earth ground will not be the same. I could get 480 V or I could get something much higher or much lower.

It is important to use a common ground for all wiring in a location so that the voltage potential stays the same. When we add a ground to a circuit, it pulls the voltage to the same potential. If I want my 24 VDC to be on the same potential as my 120 VAC, I would need to ground my 24 VDC - to the 120 VAC ground. Then both the 24 VDC and 120 VAC can be referenced to ground.

In order to fix the problem of where the 480 V could be a different potential, we would run a ground out 2 miles to ensure the same 480 V is at the factory and is 2 miles away. For some jobs, integrators or OEM's will bond all of their equipment to a metal skid, so during installation, the ground is connected to the skid.

The difference between bonding and grounding is that bonding connects wires to a grounding point. Whereas grounding actually is connected back to earth. Essentially bonded items are not grounded until a ground is added. Then, all the bonded items will have the same potential as referenced by the added ground.

Examples

Grounding is very important. It helps to prevent fires as well as protect lives. Here are a couple of personal examples of grounding problems.

 | Example: Shocking Outlets |
 | My wife was taking care of our rabbits when she noticed she was getting shocked by the outlet used to plug the heated water for the rabbits. I went and looked at it. The ground was attached to the outlet, but the wire itself never made it back to earth ground. I fixed the wiring and the shocking outlet went away. |

 | Example: Arcing |
 | Once my kids turned on the light in the kitchen, and it started to arc. My wife quickly turned off the light. Had this happened at a time when no one was present, it could have burned the house down. The problem was that a hot wire came loose and touched the metal housing of the light, so the light was not grounded. If it had it been grounded, it would have tripped the breaker and protected my home and family. As you can see, grounding is very important. |

According to the NFPA, in 2016, there were 45,300 fires caused by electricity which accounted for 480 deaths. See the following link for the full report:

https://www.nfpa.org/-/media/Files/News-and-Research/Fire-statistics-and-reports/US-Fire-Problem/Fire-causes/osHomeElectricalFiresTables.pdf

Lab Information

Failure to ground where required will result in a failure of a lab and you will be required to redo it.

 | Important! |
 | Every time that you use a 2-way switch, 3-way switch, 4-way switch, or 120 V receptacle, you will be required to ground them. This is regardless of any drawing or what any other instructor says. |

 | Warning |
 | Always make sure to ground properly! |

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