RCD Keeps Tripping? 7 Common Reasons Why

An RCD (Residual Current Device) is designed to trip when it detects current leaking to earth — it's saving lives every time it does. But an RCD that trips repeatedly, or trips for no obvious reason, is telling you something is wrong. Here are the seven most common causes and what you should do about each.

What Is an RCD and Why Does It Trip?

An RCD monitors the current flowing through the active and neutral conductors. If those two values differ by as little as 30 milliamps — meaning current is finding another path (through a person or to earth) — the device trips the circuit in milliseconds. That speed is what makes it effective at preventing electrocution.

7 Common Reasons Your RCD Keeps Tripping

1. Faulty Household Appliance

This is the most common cause. A worn power cord, damaged internal wiring, or a failing motor in a washing machine, dishwasher, or kettle can cause small amounts of current to leak to the casing. Test by unplugging all appliances on the tripped circuit one at a time — when the RCD stops tripping, you've found the culprit.

2. Moisture or Water Ingress

Water and electricity don't mix. Rain getting into an outdoor power point, condensation inside a light fitting, or a leaking pipe above the ceiling can all cause leakage current. RCDs protecting bathroom and external circuits are especially prone to moisture-related trips.

3. Deteriorated or Damaged Wiring

Old wiring with cracked insulation, or cables damaged by pests, DIY renovations, or corrosion, can develop earth leakage over time. This is a serious issue that requires a licensed electrician to locate and repair.

4. Earth Leakage from Multiple Small Loads

Every piece of electrical equipment has a small, normal amount of leakage current to earth. In a property with many appliances on a single RCD, these small amounts can add up and approach the 30mA trip threshold. The solution is usually to redistribute loads across additional RCDs.

5. Nuisance Tripping (RCD Sensitivity)

Older RCDs can become overly sensitive with age and trip below the 30mA threshold. If the device has been in service for many years and trips even with the board disconnected from the property wiring, the RCD itself may need replacement.

6. Wiring Installation Errors

A neutral conductor connected to earth downstream of an RCD will cause it to trip immediately or intermittently. This type of wiring error is usually the result of unlicensed electrical work and must be corrected by a licensed electrician.

7. Overloaded Circuit

While RCDs primarily protect against earth leakage (not overload), some combined RCBO units offer both functions. If your device is an RCBO, heavy loads — such as multiple high-draw appliances on one circuit — can cause tripping even without a leakage fault.

When an RCD Trips During a Safety Inspection

During a mandatory electrical safety check, our technicians test RCDs as part of the inspection. We verify trip time, trip current, and the condition of the device itself. If an RCD is found to be faulty or missing from circuits that require protection, we'll note this in the report so it can be rectified.