What Is a Ground Fault and Why Is It Dangerous?

What Is a Ground Fault and Why Is It Dangerous?

A ground fault occurs when electrical current flows outside its intended path — through a grounded surface, a water pipe, a wet floor, or a person — instead of returning through the neutral conductor. Ground faults are a leading cause of electrical shock injuries and fires. Understanding what causes them and how to protect against them is essential for any homeowner.

How a Ground Fault Happens

In a properly wired circuit, current flows from the panel through the hot wire to the load (a light, appliance, or outlet) and returns through the neutral wire. A ground fault interrupts this path — current leaks to an unintended conductor that is connected to ground, creating a parallel path outside the wiring system.

Common causes include:

• Damaged or deteriorated insulation on a wire touching a metal enclosure, appliance chassis, or wet surface
• Water intrusion into an outlet, light fixture, or appliance
• A frayed cord where the conductor contacts a grounded metal surface
• An appliance with an internal wiring fault causing the chassis to become energized

Why Ground Faults Are Dangerous

The human body is an effective conductor of electricity, particularly when in contact with a grounded surface (standing on a wet floor, holding a water pipe, or touching a grounded appliance). When a ground fault current finds a path through a person:

• As little as 10 milliamps (0.01 amps) can cause muscle lock — preventing a person from releasing the conductor
• 100 milliamps (0.1 amps) can cause ventricular fibrillation and death
• Standard 15- and 20-amp circuit breakers do not trip at these current levels — they are designed to protect wiring, not people

GFCI Protection: The Defence Against Ground Faults

Ground Fault Circuit Interrupters (GFCIs) monitor the difference in current between the hot and neutral conductors. If they detect a difference of as little as 5 milliamps — indicating current is leaking to ground — they trip in approximately 1/40 of a second, before lethal current levels can affect the heart.

The Ontario Electrical Safety Code requires GFCI protection in locations where ground fault risk is elevated:

• Bathrooms (all receptacles)
• Kitchens (countertop receptacles within 1.5 metres of a sink)
• Garages and carports
• Outdoor receptacles
• Unfinished basements and crawl spaces
• Areas within 1.5 metres of pools, hot tubs, and spas

Ground Faults vs Overloads: Why a Breaker May Not Protect You

A standard circuit breaker trips when current exceeds its rated amperage — typically 15 or 20 amps. A ground fault through a person involves far less current than this threshold. A breaker will not protect a person from a ground fault shock. Only a GFCI device operates at the sensitivity required to prevent electrocution.

EZSMART installs GFCI outlets and breakers for residential and commercial properties across Ontario. Contact us if your home lacks GFCI protection in required locations.

Amir Azimipour

Electrician Since 2008 Journeyman Electrician Designated Master Electrician at EZSMART Corp