Why your circuit breaker or GFCI keeps tripping, and what to do safely

What’s in the breaker panel

The breaker panel (or consumer unit, or fuse box) is the box of switches usually near the entrance of the home. In Spain, for example, the Low Voltage Electrical Regulation (ITC-BT-25) requires homes to have at least:

1. A main breaker of at least 25 A, protecting the whole home against overloads and short circuits.
2. One or more residual current devices covering every circuit, with a sensitivity of 30 mA at most.
3. A breaker for each circuit: 10 A for lighting, 16 A for general outlets, 25 A for the stove and oven, 20 A for the washing machine, dishwasher and water heater, 16 A for the bathroom and kitchen, and 25 A for heating or air conditioning if there is any.

In other countries the names and amps differ, but the idea is the same: one breaker per area of the home and a device that watches for leaking current. In the U.S., the CPSC recommends GFCIs in kitchens, bathrooms and other places where the risk of shock is higher; they can be built into the outlet or into a breaker in the panel. Some homes also have AFCIs: according to the Consumer Product Safety Commission (CPSC), these are special breakers that detect the sparking (arcing) of a damaged wire or connection, which could overheat unnoticed and start a fire.

Why a circuit breaker trips

It trips for one of two reasons:

• Overload: you’ve switched on more appliances at once than that circuit can take. The sum is the same as for a power strip: amps × voltage = watts it can take. A 15 A circuit at 120 V takes 15 × 120 = 1,800 W. If you have a kettle (2,000 W) on it, it trips on its own; a toaster (950 W) plus a space heater (1,500 W) add up to 2,450 W: it trips. A 16 A circuit at 230 V takes 16 × 230 = 3,680 W.
• Short circuit: a damaged wire or appliance lets the current flow where it shouldn’t, with nothing to hold it back. Then it trips instantly, as soon as you plug in or switch on that appliance.

You can add up what you have plugged in with the power strip calculator: it works for a circuit too, using its breaker’s amps as the limit.

Why a GFCI or RCD trips

A GFCI compares the current going out to the appliances with the current coming back. If they don’t match, some of it is leaking: through an appliance’s casing, through water or through a person. The CPSC explains that a GFCI cuts the power with a difference of just 0.006 amps, “faster than a blink of an eye”, before the current can affect your heartbeat. According to the CPSC, ground faults most often come from damaged or defective equipment whose live parts are no longer properly protected.

So it isn’t a fault in the GFCI: it’s doing its job. Common causes are a broken or damp appliance, or water where it shouldn’t be (an outdoor outlet in the rain, a leak into a junction box).

What you can do, step by step

1. See which one has gone off: the main switch, the GFCI/RCD, or a circuit breaker.
2. If it was a breaker: switch off or unplug what you were using in that area and switch it back on. Then turn appliances on one at a time, not all the big ones together.
3. If it was the GFCI/RCD: unplug the appliances in the area where you were when it tripped and reset it. If it trips again when you plug in one particular appliance, that appliance is the problem: stop using it and have it checked.
4. Do it with dry hands and not barefoot on a wet floor.

What you should never do

• Fit a bigger breaker or fuse to stop it tripping. The CPSC explains that the wrong size fuse lets too much current through and the wiring overheats, which is a fire hazard. The breaker is chosen for that circuit’s wiring.
• Hold the switch on, bypass the GFCI/RCD or leave it off “because it keeps tripping”.
• Open the panel cover or touch wires. That’s a job for an electrician.

Test your GFCI

The test button (marked T or Test) checks that the GFCI cuts the power. The CPSC recommends testing them at least once a month, after a power cut and as the manufacturer says: when you press the button, a lamp plugged into it should go out; then you reset it. If it doesn’t cut the power, it needs replacing, and the CPSC says a qualified electrician should do it. It warns they can fail without showing any sign.

The CPSC also advises switching each breaker off and on three times at least once a year so they don’t seize up, turning off the fridge, freezer and air conditioner first, because their motors can be damaged by repeated power cuts.

When to call an electrician

• The breaker or GFCI trips again with nothing plugged in, or won’t stay on.
• It trips often even though you don’t have many appliances on.
• An outlet or switch is warm: according to the CPSC, it may be a loose connection that could start a fire. Stop using it until it’s checked.
• An appliance has given you a shock: the CPSC treats this as a sign of an extremely hazardous fault. Don’t touch it and switch off its circuit at the panel.
• The GFCI doesn’t cut the power when you press its test button.

To see how much each appliance draws before switching several on at once, read watts, kWh, volts and amps and use the electricity usage calculator.