EZSMART Corporation, ESA/ECRA #7012690 , North York , Ontario
Mon-Fri 08:00 AM - 05:00 PM
Every NMD-90 cable in an Ontario home contains a bare copper conductor tucked in with the insulated black and white wires. Most homeowners never think about it — it does not carry current in normal use, does not connect to any switch or fixture control, and looks like an afterthought. But that bare copper is one of the most important pieces of the residential electrical system, and it saves lives every day without anyone noticing. This guide walks GTA homeowners through what the bare copper wire does, why the Ontario Electrical Safety Code requires it everywhere, and what happens when it is missing or disconnected.
Direct answer: the bare copper conductor is the equipment bonding conductor. Under normal operating conditions it carries no current. Under a fault condition (a hot wire touching a metal appliance case, for example), it provides a low-resistance path back to the panel that trips the breaker and prevents the metal from becoming energized. Without the bond, a shorted appliance stays hot and the user gets shocked.
Direct answer: when a hot conductor accidentally contacts a bonded metal surface, current flows from the hot through the bond back to the panel neutral (which is bonded to the ground at the main service). The resulting current is momentarily high — typically hundreds of amps — and the breaker trips within a fraction of a second. Without the bond, no return path exists, no high current flows, and the breaker does not trip. The metal stays energized until someone touches it and provides a return path through their body.
Direct answer: Section 10 of the Ontario Electrical Safety Code requires every metal enclosure, box, fixture, and appliance case in a residential installation to be bonded. Missing a single bond point defeats the entire safety chain. A single bonded pathway from device to panel is what makes the whole home safe.
The Electrical Safety Authority lists missing or improper bonding among the top serious writeups on residential inspections. It is one of the most frequently violated code sections in DIY work.
Direct answer: two-prong receptacles from before about 1970 have no equipment bond terminal because the branch cable did not include a bond. These are still legal in Ontario, but the receptacle cannot accept three-prong appliances. Upgrading to three-prong receptacles requires either running a new bond conductor or installing GFCI protection with a “No Equipment Ground” label per OESC.
Homes with knob and tube wiring almost always have two-prong receptacles throughout. Our post on knob and tube covers the migration path.
In our experience diagnosing shock complaints across GTA homes, the single most common cause is a missing or disconnected bond somewhere in the circuit. Homeowners feel a mild tingle from an appliance case, they replace the appliance, tingle continues. The problem is not the appliance — it is the bond conductor that was never terminated at some point in the circuit. We trace back through devices and boxes until we find the missing bond, restore it, and the tingle disappears. Never ignore any electrical tingle from a metal object; it is telling you the bond is compromised. Our post on wiring colour convention covers the related colour identification.
Suspect a bonding issue in your GTA home, or feeling a tingle from a metal appliance? Book an ESA-certified electrician the same day. Call us at 416-838-9006 or visit our contact page — we will get back to you the same day.
Electrician Since 2008 Journeyman Electrician Designated Master Electrician at EZSMART Corp
