How to reset a tripped consumer unit

Glossary · Consumer units and protection

How a trip and a reset work

A circuit breaker or an RCD trips to cut the supply when it detects a fault. The IET says that if one trips, it is likely to be a fault with an appliance connected to the installation, not the installation itself. Faults on the installation can still happen, and they are more likely after DIY such as hanging pictures or shelves.^{[1]IET, Consumer units: safe fuse-box upgrades for modern homes}

The tripped device is the switch that has moved to the off position. Resetting means switching it back on. The device will only stay on if the cause has gone. For the reasons a device trips again and again, see why does my RCD keep tripping.

What you can check yourself

The IET describes a simple fault-finding routine that a householder can do without opening anything.^{[1]IET, Consumer units: safe fuse-box upgrades for modern homes}

1. Unplug every appliance on the affected circuit. Take each plug fully out of the socket. Turning the appliance off at the socket is not enough.
2. Reset the affected circuit breaker or RCD.
3. If it stays on, plug the appliances in one at a time.
4. The appliance that trips it again is the faulty item. Do not use it until it has been repaired.

The IET adds one caution. Resetting a circuit breaker or RCD on a fault repeatedly could damage the device. Keep the number of attempts to a minimum before asking a registered electrician for advice.^{[1]IET, Consumer units: safe fuse-box upgrades for modern homes}

If a lighting circuit tripped, the IET says the cause could be a blown or failed lamp, which is more common with older tungsten lamps. Resetting the device and checking the fittings would then show the lamp was at fault.^{[1]IET, Consumer units: safe fuse-box upgrades for modern homes}

You can also test an RCD by pressing its button marked T or Test. The device should switch off. The IET says to do this every six months and that doing it when the clocks change covers it twice a year.^{[3]IET, BS 7671 FAQs: Consumer Units and Protective Devices}

When to call an engineer

Call a registered electrician if:

• the device will not reset with everything unplugged
• it trips again after you have removed the suspect appliance
• the RCD test button does not switch it off
• you think DIY work may have damaged a cable

The IET says that if the device does not reset with everything unplugged, a registered electrical contractor can test the installation and diagnose the fault.^{[1]IET, Consumer units: safe fuse-box upgrades for modern homes} Electrical Safety First gives the same advice for an RCD that keeps tripping.^{[2]Electrical Safety First, FAQ for electrical safety: your questions answered}

If you notice a burning smell, excessive heat, smoke, or evidence of burning or charring, the IET says the installation should be isolated immediately and without delay, and a registered electrical contractor consulted. It describes the main switch as a way to isolate the whole installation in an emergency.^{[1]IET, Consumer units: safe fuse-box upgrades for modern homes} Do not open the consumer unit. NICEIC says any installation, replacement or repair of a consumer unit needs a registered electrician.^{[4]NICEIC, Consumer units and fuse boxes: installation and replacement}

Martin Day Electricians has an emergency electrician service in Leeds for faults that cannot wait.

Example

Chloe in Kirkstall finds the downstairs sockets dead. At the consumer unit, one switch is in the off position. She unplugs the kettle, toaster, microwave and a heater from the kitchen sockets, then switches the device back on. It stays on.

She plugs the items in one at a time. When the heater goes back in, the device trips. She leaves the heater unplugged and does not use it. Had the switch not stayed on with everything unplugged, she would have called an electrician.

What people get wrong

The most common mistake is switching the device back on again and again until it holds. A device that keeps tripping is reporting a fault. Repeated resetting can damage it and does not remove the cause.

A second mistake is to assume the wiring is at fault. The IET says a trip is more likely to be an appliance, so the one-at-a-time check is worth doing before a call-out.^{[1]IET, Consumer units: safe fuse-box upgrades for modern homes}

The bottom line

To reset a tripped consumer unit, unplug the appliances on that circuit, switch the device back on once, then plug them in one at a time to find the faulty one. Do not open the unit. If it will not reset, trips again, or there is any sign of burning, call a registered electrician.