Ground Fault Circuit Interrupters (GFCI)


Ground Fault Circuit Interrupters, commonly known as “GFCI”.


Today I will explain why certain electrical circuits need special protection. The devices used when special protection is required are called Ground Fault Circuit Interrupters. By the end of this blog, hopefully you will have a better understanding of what a ground fault is, what is a GFCI, the types available, and where to install.



Let’s start with a very basic analogy about electricity in our homes:

Electrical flow is similar to water flow in a closed loop system.  First look at water flow, see the left side of the diagram. When pressure is applied against a section of the pipe, water will be pushed and will flow to the fixture (“reduced flow”). After the fixture it flows back to the source. This is called a closed system in plumbing. An example of this type of plumbing is piping used for boiler heating.



The same can be said for electrical flow:

When a charge or pulse (power source) at one end of the wire occurs, the charge will produce movement and electrons (electrical flow, yellow arrows) will flow from one end of the wire to load (ex. a light bulb) and flow back to the original source.



Look at the switch and the valve in previous the picture.

The purpose of a closing a valve in a water system is to stop flow. In an electrical system the opposite needs to happen. The switch would need to open to stop electrical flow. Electrical circuits are normally opened/stopped by devices such as switches, fuses or circuit breakers.  What happens if switch in the circuit doesn’t open? What if more than expected electrical flow occurs through the both the supply and return wires?



The addition of “Ground Wire” helps.

Most circuits in newly built homes have the addition of a ground wire that leads to a ground point. Often terms such as “ground”, “ground conductor”, “grounded conductor”, “un-grounded conductor” and a “ground fault” are misunderstood.


Electrical diagram explaining Ground


Defining each term as easily as possible is important:


  • Ground: Simply refers to earth.  It is an essential part of the safety “Earthing system“.


  • Ground Conductor : A wire that is not a part of the normal path of the circuit,  it does NOT carry normal current. When a ground wire does carry current, it is taking care of a dangerous situation. It is supposed to carry a lot of flow suddenly, so that it causes the breaker (switch) of the circuit to open (trip). Thereby also alerting you that a problem needs attention.
  • Grounded Conductor:  Called a “neutral”  it is used for carrying power back to the panel/source to complete the circuit. CONNECTED to ground inside the panel. It is integral to equipment operation, but it has nothing to do with safety.
  • Un-Grounded Conductor: Carries power (electrical flow) to the load. It is NOT CONNECTED to ground. Known as “hot” wire.
  • Ground Fault:  Is a “leaking” of current off of it’s intended path, by way of something other than the neutral wire. For example, an un-grounded hot wire touches a metal box, this would electrify the box. The metal box is now “hot”, if a person touches the box they get shocked!



Adding GFCI to prevent ground fault shocks.

To avoid electrical shocks from ground faults, ground fault circuit interrupters (GFCI) are required to be installed in our homes. When these automatic devices detect a ground fault, it will stop or “interrupt” the electrical flow immediately. You may still feel a shock but this device will stop it before it becomes lethal.


Types of ground fault circuit interrupters

Three types of Ground fault circuit interrupters are used in homes. Each has a different application, however they all preform the same function.

ground fault circuit interrupters types

1. GFCI Outlet:  Similar to a standard outlet, a GFCI outlet will protect any appliance that is directly plugged           into it. One GFCI outlet can protect several other outlets if wired properly.


2. GFCI Circuit Breaker:  A special circuit breaker located in the main electrical panel that protects the entire           circuit, so that GFCI outlets are not required in the circuit.


3. Portable GFCI: This type of GFCI is used for mobile situations. It is commonly used in the construction               industry, but can be helpful to add temporary GFCI protection in areas of home where GFCI doesn’t exist.           NOTE: This type of GFCI is NOT allowed to be used as permanent wiring.



Where to Install?

Today’s building standards require ground fault protection in areas where deadly shocks are like to happen, such as all exterior outlets, bathrooms, kitchens near water sources, laundry areas and inside garages.

In conclusion, by using GFCI protection in wet environments you can greatly decrease the chances of deadly shocks in your home.

Thanks for reading. Look out for my next blog, I will be explaining Arc Fault Circuit Interrupters (AFCI).


Author: Geoff Bohaker at Shelter West Home Inspections


About Geoff Bohaker

Geoff is the owner and operator of Shelter West Home Inspections in Vancouver, B.C., Canada. His boundless curiosity for buildings and how they interact as complete systems, guide him on his journey to educate his clients on making the most informed home decisions possible.