RCD fault finding guide.

What to do if your RCD trips.

It can be very inconvenient when an RCD trips, but it is an indication that a circuit in your property has a fault. The most common problem that causes an RCD to trip is faulty appliances, but there can be other underlying causes. If an RCD trips to the ‘OFF’ position you can follow these steps:

1. Try resetting the RCD

Toggle the RCD switch back to the ‘ON’ position. Some older RCDs trip to a mid position and require the switch to be pushed down and then up to reset the device. If the problem with the circuit was a temporary one, then this may be the solution.

2. Isolate the circuits

If this does not work, and the RCD immediately (or after a short period of time) trips again to the ‘OFF’ position:

• Switch all the MCBs that the RCD is protecting to the ‘OFF’ position.
• Reset the RCD as described above.
• Switch the MCBs to the ‘ON’ position, one at a time.

When the RCD trips again, you will be able to identify which circuit has the fault. You can then call an electrician and explain the problem.

3. Locate the faulty appliance

It is also possible to try and locate the faulty appliance. You do this by unplugging everything in your property, resetting the RCD to ‘ON’, and then plugging back in each appliance one at a time. If the RCD trips after plugging in and switching on a particular appliance, then you have found your fault. If this does not resolve the problem, you should call an electrician for help.

This is an example of an RCD that trips to a mid-position, which requires the toggle switch to be pushed down, then all the way up to reset the device.

Remember, electricity is extremely dangerous and all problems need to be taken seriously and never ignored. If you are unsure, it is always best to call a professional electrician. We are a trusted, local NICEIC approved electrician offering a wide range of domestic and commercial electrical services for our customers.

Consumer units with RCDs

Modern domestic consumer units (fuse boxes) are usually fitted with one or more RCDs (residual current devices). If yours doesn’t contain any RCDs / RCBOs, or has limited protection to some circuits, you should definitely consider upgrading your consumer unit to one that does.

An RCD / RCBO plays an important part in electrical safety. Its purpose is to protect you from a potentially fatal electric shock, and your property from electrical fires. It does this by constantly monitoring the electric circuits in your property for leaking current caused by earth faults within plugged-in appliances, permanently connected appliances, light fittings, and the fixed wiring. It is an extremely sensitive piece of equipment and can detect even the tiniest current leakage of more than 30mA. If an RCD / RCBO detects an earth leakage fault it will automatically cut off the electricity to the circuit or group of circuits with the fault.