Electrical Terms Glossary
Electrical Terms Glossary
Reference
The vocabulary that turns up on quotes, inspection reports and forum threads — defined plainly, with the Ontario specifics that actually matter.
Electrical quotes and inspection reports are full of terms nobody explains. This is the vocabulary we find ourselves defining most often on site, written out plainly. Where a term has an Ontario-specific wrinkle — and several do — it is noted.
A breaker that detects the electrical signature of an arcing fault — the kind of low-current fault a conventional breaker ignores and that starts fires inside walls. The Canadian Electrical Code has progressively expanded where AFCI protection is required in homes.
No AFCI breaker is made in the Stab-Lok format, which is the practical reason to replace those panels.Aluminum conductors used for branch circuits, common in homes built roughly 1965–1978. It is permitted by the Ontario Electrical Safety Code and the ESA calls the idea that it is recalled or inherently a fire hazard a myth.
Failures happen at terminations, not along the conductor. The remedy is correct devices and technique.The maximum current a conductor can carry continuously without exceeding its temperature rating. It is what determines wire size for a given breaker, not the other way round.
Electricity flowing from a home back onto the utility network — most often from a generator connected without a transfer switch. It can energise lines that crews believe are dead.
This is the single reason generator connections are regulated the way they are.Connecting conductive parts together so there is no voltage difference between them. Distinct from grounding, and critical around pools, where every conductive part must be tied into a bonding grid.
Missed bonding is the commonest serious defect in pool installations and is very hard to add afterwards.The demand a dwelling is expected to place on its service, worked out under the Canadian Electrical Code from floor area plus specific loads — range, dryer, water heating, air conditioning, EV charger — each with its own demand factor.
This, not the number of empty breaker spaces, decides whether a service can take a new load.A marking on switches and receptacles certifying them for direct connection to aluminum conductors. Devices marked AL-CU serve a similar purpose on larger terminations.
How accurately a light source renders colour compared with natural light, on a scale to 100. Fixtures at 90+ make a visible difference to how skin, wood and stone look.
A circuit serving one appliance or one location and nothing else. The Code requires them for particular loads — kitchen counter receptacles, bathrooms, laundry, EV chargers.
The boundary between the utility's equipment and yours. In Ontario the utility generally owns everything up to and including the meter; the service entrance, panel and everything beyond are the homeowner's.
It decides who you call, and who pays, when something fails.Two conductors landed under a single breaker terminal that is rated for one. A common defect found during inspections and an easy fix, but a sign the panel has run out of room.
The conductor that gives fault current a deliberate low-resistance path back to the source so a breaker trips. Knob-and-tube systems have none, which is why three-prong receptacles on those circuits are often not truly grounded.
Ontario's electrical regulator. Electrical work in Ontario is notified to the ESA and inspected by the ESA — there is no separate municipal electrical permit.
A licensed contractor files the notification under their own licence number.A conductor set running between a main panel and a sub-panel, as opposed to a branch circuit running from a panel to devices.
An overcurrent device that protects a circuit by melting. Legal and still in service in many owner-occupied Ontario homes. The practical problems are over-fusing and the inability to fit modern protective devices.
A device that cuts power when it detects current leaking to ground, typically within milliseconds. Required near water — bathrooms, kitchens, outdoors, pools.
It protects people. A regular breaker protects wiring.Certification that a recessed light fixture may sit in direct contact with thermal insulation. IC-rated fixtures carry a thermal protective device; non-IC fixtures must be kept clear of insulation by the manufacturer's specified distance.
Any top-floor ceiling under an insulated attic needs IC-rated fixtures.The utility disconnecting the service so work can be done safely at the service entrance. It is scheduled by the utility, not by your electrician, and is usually the longest item in a service upgrade.
Early wiring using porcelain knobs to hold single conductors clear of framing and porcelain tubes where they pass through it. The spacing is functional — the system sheds heat into open air.
The ESA permits it to remain under three specific conditions. It must never be buried in insulation.Equipment that monitors total household current and reduces or interrupts a large load — typically an EV charger — when the rest of the home draws heavily, so the service is never exceeded.
Frequently a far cheaper answer than upgrading a service.The vertical conduit carrying overhead service conductors from the weatherhead down to the meter base. On older homes it is often undersized for a modern service and replaced as part of an upgrade.
The enclosure holding the utility meter. On a service upgrade an indoor meter must be relocated outdoors.
The grounded circuit conductor that carries current back to the source. Under the current Code the neutral is grounded at one location only.
ESA stopped accepting meter-base bonding through the neutral in October 2025.The regulation governing electrical installations in Ontario, based on the Canadian Electrical Code with Ontario-specific amendments. Updated on a regular cycle.
The breaker or fuse that protects a conductor from carrying more current than it is rated for. Fitting a larger fuse to stop nuisance blowing removes the protection entirely.
A short conductor joining existing wiring to a device through a connector rated for the purpose. The standard remedy for aluminum branch wiring — a copper pigtail lets an ordinary device be used safely.
Everything bringing power from the utility connection into the panel: conductors, mast or underground feed, weatherhead and meter base. On older homes it is frequently replaced along with the panel.
The current rating of the supply to a home, in amps — commonly 60, 100 or 200 in Ontario housing. Toronto Hydro caps overhead residential services at 200 amps.
Larger than 200 amps means an underground supply, with the customer paying the civil work.A breaker and panel format made by Federal Pioneer in Canada. There is no Canadian regulatory recall of Stab-Lok panels; two narrow voluntary breaker recalls exist and are routinely misreported as panel recalls.
Schneider Electric still sells Stab-Lok breakers new in Canada.A secondary panel fed from the main panel, used to serve a garage, a basement suite or an outbuilding. Often a better answer than running long individual circuits.
A breaker fitting two circuits into one panel space. Useful, but widespread use of them is a reliable sign the panel has run out of capacity.
The device that switches a home between utility supply and generator, making it physically impossible for both to be connected at once. Required for any permanent generator connection.
The loss of voltage along a long conductor run. Past allowable limits it forces a larger conductor than the breaker rating alone would suggest — common on deep lots and detached garages.
The fitting at the top of a service mast where overhead conductors enter, shaped to keep water out. Replaced along with the mast on most service upgrades.
Grounding connects a system to earth and gives fault current a path back to the source so a breaker trips. Bonding connects conductive parts to each other so there is no voltage difference between them. Around a pool, bonding is what stops a difference in potential between a ladder, the water and the deck — a separate requirement from grounding.
A circuit serving one appliance or one location and nothing else. The Ontario Electrical Safety Code requires dedicated circuits for particular loads — kitchen counter receptacles, bathrooms, laundry and EV chargers among them — so a single heavy appliance cannot trip a circuit shared with half the house.
No. A GFCI detects current leaking to ground and cuts power within milliseconds — it protects people, and is required near water. An AFCI detects the signature of an arcing fault, the kind a conventional breaker ignores, and protects against fires starting inside walls. Some locations require both.
The demand a home is expected to place on its electrical service, worked out under the Canadian Electrical Code from floor area plus specific loads such as a range, dryer, water heating, air conditioning and an EV charger, each with its own demand factor. It — not the number of empty breaker spaces — decides whether a service can take a new load.
It identifies a licensed Electrical Contractor registered with the Electrical Safety Authority. Only a licensed contractor may file notifications and take responsibility for electrical work in Ontario. Ours is ECRA/ESA 7014949. If a contractor cannot give you a licence number, that is a meaningful warning sign.
What the line items on a quote actually represent.
Read more →Who files what, and how the inspection process runs.
Read more →The three conditions, and why insurance decides most rewires.
Read more →Related services: Electrical Inspections · Panel & Service Upgrades · Is This an Electrical Emergency?.
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