What you will know after this guide

  • The four concepts
  • Breaker, fuse, GFCI and AFCI
  • Reset a breaker
  • Replace a fuse

The four concepts

  • Voltage, in volts: electrical potential that drives current.
  • Current, in amperes: electrical flow in a circuit.
  • Power, in watts: voltage × current for a simple load.
  • Energy, in kWh: power used over time.

A circuit rating is not a target for continuous use.

Breaker, fuse, GFCI and AFCI

A breaker or fuse mainly protects conductors from overcurrent. A GFCI detects leakage to ground. An AFCI detects certain dangerous arcing. They are not interchangeable and must match the panel, circuit and local requirements.

Reset a breaker

1. Note what was operating and unplug loads on the circuit.

2. Stand to the side with dry hands, dry floor and an intact panel with no odour, heat, water, sound or smoke.

3. Move the handle fully OFF, then ON once.

4. Reconnect loads gradually.

5. If it trips again, leave it OFF and call a professional.

Replace a fuse

Never increase amperage, alter the base or use a substitute object. Identify the cause, turn off loads and use only the type, voltage, class and amperage allowed by the panel and local rules. A damaged, hot, corroded or unknown fuse holder belongs to an electrician.

Select the correct rating

The protective-device rating depends on conductors, temperature, load, circuit type and panel; it is not chosen based on the appliance that trips it. Oversized protection can let conductors overheat before opening.

Stop immediately

Water in the panel, arcing marks, buzzing, odour, heat, corrosion, missing cover, exposed conductor, exploding fuse or repeated trips: do not open or touch; have it made safe. DIY and inspection rules vary by province.

Verified references