EZSMART Corporation, ESA/ECRA #7012690 , North York , Ontario
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Extension cords that are coiled and stored incorrectly develop kinks, internal wire damage, and insulation stress that shortens their usable life and creates fire hazards. Proper coiling technique preserves the cord’s geometry, keeps the insulation intact, and makes the cord tangle-free when it is next unrolled — which matters both for ease of use and for safety.
The most common coiling mistake is wrapping the cord in tight circles around your arm or hand. This creates a coil that holds a twist — every loop adds a half-twist to the cable that stores energy in the insulation and conductor. When the cord is unrolled, it fights back by kinking, twisting, and tangling. The correct technique eliminates stored twist before it enters the coil.
Professional electricians and audio/video technicians use a technique called over-under coiling, which alternates the direction of each loop to cancel out the twist that builds up in simple circular coiling. Here is the procedure:
Coiling a cord in one consistent direction forces the cord to hold a twist. Over hundreds of coiling cycles, this repeated stress concentrates at the same point in the cord — typically at the transitions between the coil loops. The conductor strands inside the cord fatigue and eventually break, usually while the cord is still carrying current. A broken conductor strand inside a cord that appears intact on the outside is one of the harder-to-diagnose cord faults. It causes intermittent power loss at certain positions (when the broken strands lose contact), arcing at the break point, and heat generation inside the insulation.
Heat from internal arcing in a cord is the mechanism behind cord-related fires. The outer insulation contains and transfers the heat to surrounding materials rather than releasing it to the air. This is why a cord that feels warm or hot at one point along its length — not at the plug, but at a point along the cord — should be taken out of service immediately.
Extension cord failures are more common when the cord is undersized for the load or the length. A longer extension cord has more resistance than a shorter one of the same gauge, which means it carries less current to the device at the end — and generates more heat doing it. The Ontario Electrical Safety Code (OESC) requires that extension cords be rated for their intended load. Practical guidance:
When we inspect electrical systems in older homes, we frequently find extension cords that have been in storage for years in a tangled, compressed state — coiled by someone who wrapped them tightly around the cord body and then stuffed them into a drawer or box. When those cords are retrieved for use, the kinks from storage make them almost unusable, and the conductor damage from years of stored stress makes them unsafe. A cord that has been stored badly — compressed into a tight bundle, stored kinked, or wrapped around a nail so tightly that the loops are forced into sharp angles — should be inspected carefully and, if the jacket shows any cracking or stiffness, replaced rather than used. Cord insulation that has lost its flexibility is insulation that is failing. See our guide on why extension cords cannot replace permanent wiring for context on when a cord problem is actually an outlet problem in disguise.
Need electrical safety advice or an inspection in the GTA? Our ESA-licensed electricians are available. 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
