My RCD keeps tripping — what to do, step by step

Your RCD has tripped and you have lost power to part of the house. Before anything else: your RCD has not broken. It has done exactly what it is designed to do — it detected something wrong and cut the power to protect you. Take a breath. This guide walks you through the process calmly, one step at a time.

What it means when your RCD trips

An RCD — Residual Current Device — constantly monitors the flow of electricity through a circuit. Under normal conditions, the current flowing out along the live conductor and returning along the neutral conductor is equal. The instant any current leaks elsewhere — through a faulty appliance, through damaged cable insulation, or through water — the RCD detects the imbalance and cuts the power in approximately 30 milliseconds.

That is fast enough, in most cases, to prevent a fatal electric shock. The RCD tripping is not a malfunction. It is a success. The device has protected you.

What the trip is telling you is that at the moment it operated, something caused current to leak to earth on the circuit it protects. Your task now is to find out whether that fault is still present — or whether it was a transient event, such as a brief moisture contact or a momentary spike, that has already resolved itself.

Two scenarios: clean trip vs. live fault

Before you attempt a reset, it helps to understand which situation you are in. The approach — and the outcome — is different for each.

Scenario A — clean trip

The cause has already gone. Perhaps an appliance briefly developed a fault and then recovered. Perhaps a power surge triggered the device. Perhaps moisture briefly contacted a circuit and has since dried. In this case, the RCD will reset and hold when you try it. Power is restored. You should still investigate what caused the trip — because if it happens again, the cause is still there — but you are not in immediate danger.

Scenario B — live fault

The fault is still present. The RCD will trip again immediately when you try to reset it — sometimes before the switch even reaches the fully on position. This is the RCD continuing to protect you. Do not force the switch or hold it in position. There is a fault that needs to be identified and isolated before power can be safely restored to that circuit.

Step 1 — How to attempt a reset correctly

The RCD switch is on your consumer unit — the grey or white plastic box (also called the fuse box or distribution board) that houses all your circuit switches. This is typically in a hallway, under the stairs, in a utility cupboard, in a garage, or in a meter cupboard.

The RCD is the larger switch on the unit, usually labelled “RCD”. When it has tripped, it will be in the down position or in a middle position between on and off. The smaller switches arranged beside or below it are MCBs (Miniature Circuit Breakers), which protect individual circuits.

Step 2 — If it will not stay up: the MCB isolation method

The RCD is tripping instantly because it is still detecting leakage current somewhere on the circuits it protects. To find out where, you need to remove those circuits from the equation one by one, then identify which one is the cause.

Step 3 — Switching MCBs back on to find the faulty circuit

The RCD is holding with all MCBs off. Now you need to identify which circuit is carrying the fault.

Step 4 — The appliance unplugging process

You have identified the faulty circuit. Now unplug every appliance on that circuit — check every socket in the rooms fed by that circuit and remove all plugs from the sockets.

Step 5 — Hardwired appliances you cannot simply unplug

Some appliances are permanently wired to the circuit and cannot be unplugged from a socket. These include boilers, electric hobs, ovens, cooker hoods, extractor fans, and storage heaters. If the RCD trips even after you have unplugged every socket appliance on the circuit, a hardwired appliance may be the source of the fault.

Hardwired appliances must be isolated at the consumer unit — by switching off the dedicated MCB for that appliance — rather than unplugged from a socket. This process, and how to approach testing a circuit that serves both socket outlets and hardwired loads, is covered in detail in our guide to isolating hardwired appliances during fault-finding.

If you are not confident identifying which MCB serves which hardwired appliance, or if you are not sure how to proceed safely, stop here and call us. Working near live wiring without certainty about what is and is not isolated is not safe.

When to stop and call a professional

Most RCD trips caused by faulty appliances can be resolved using the steps above. But there are situations where you should stop and call a qualified electrician rather than continue investigating yourself.

• The RCD trips with every MCB switched off. The fault is on the main incomer or within the consumer unit itself. This is not something a homeowner should investigate. Call us.
• You cannot identify the faulty appliance even after unplugging everything accessible on the circuit. The fault may be in the fixed wiring, a junction box, or a hardwired appliance. It requires test equipment to locate.
• There has been a flood, a water leak, or a burning smell. Water in a consumer unit or near wiring is an emergency. Do not restore power. Call us, or if there is any risk of immediate danger, call your distribution network operator (DNO) who can isolate the supply at the meter. If you are in the Bristol area, our emergency electrician service is available for exactly this.
• The RCD trips with all appliances unplugged and all MCBs on. The fault is in the fixed wiring of the circuit rather than in any appliance. This requires cable fault location and repair by a qualified electrician.
• You are unsure at any point. There is no shame in stopping. The purpose of this guide is to help you restore power safely in straightforward cases. If the situation is not straightforward, calling a qualified electrician is the right call.

A different problem: intermittent tripping

Everything above assumes your RCD has tripped and will not reset, or trips immediately on reset. But some homeowners have a different problem: the RCD trips occasionally, apparently at random, and resets fine when they try — but then trips again days or weeks later.

Intermittent tripping is a separate problem with a different set of causes and a different diagnostic approach. Appliances with marginal insulation faults that only manifest under certain conditions (temperature, loading, moisture level) can cause this. So can high leakage current from a combination of individually acceptable appliances all running at the same time.

If your RCD trips repeatedly but always resets, rather than refusing to stay up, see our dedicated guide to intermittent RCD tripping — the approach is different and the article covers it in detail.