If your RCD switch has tripped and won’t stay up, or keeps tripping back down shortly after you reset it, there’s a fault somewhere on one of the circuits it protects. The RCD is doing exactly what it’s designed to do — shutting off power to protect you. Here’s how to figure out what’s causing it.
What does an RCD do?
An RCD (Residual Current Device) monitors the current flowing in and out of a circuit. If it detects even a small imbalance — which can indicate current flowing to earth through something it shouldn’t, like a person or a damaged cable — it trips within milliseconds, cutting the power.
RCDs are there to prevent electrocution. A tripping RCD is a warning, not an inconvenience to override.
Why won’t the RCD stay up?
The most common causes are:
- A faulty appliance. A damaged plug, a kettle or washing machine with a failing element, or any appliance with damaged insulation can cause an RCD to trip. This is by far the most common cause.
- Damaged wiring. A cable that has been nailed through, crushed, or had its insulation worn away will cause a persistent fault.
- Water ingress. An outdoor socket, garden light, or bathroom fitting that has had water get into it will often cause the RCD to trip.
- A deteriorating RCD. Older RCDs can become sensitive over time and trip under normal load. If every appliance has been eliminated as a cause, the device itself may need replacing.
How to identify which circuit is causing the problem
In a modern consumer unit, each circuit has its own breaker or RCBO. In older split-load boards, one RCD may cover several circuits. Here’s a simple process to narrow it down:
- Switch off and unplug everything connected to the circuits the RCD covers.
- Reset the RCD. If it stays up with nothing connected, the fault is in an appliance.
- Plug appliances back in one at a time. When the RCD trips again, the last appliance you plugged in is likely the cause.
- If the RCD trips immediately even with nothing plugged in, the fault is in the fixed wiring — don’t keep resetting it. Call an electrician.
When to call an electrician
- The RCD trips immediately even with all appliances unplugged
- You can’t identify a faulty appliance and the RCD keeps tripping
- The RCD trips in a specific room or after using a specific socket or light
- You can smell burning from any socket, switch or fitting
- The RCD is hot to the touch
Don’t repeatedly force an RCD to stay up if it keeps tripping — the fault hasn’t gone away, you’ve just removed the protection. If you can’t find a faulty appliance as the cause, the problem is in the wiring and needs a qualified electrician to trace and fix it.
We carry out electrical fault finding across Bristol and South Gloucestershire. Get in touch and we’ll get it diagnosed.
