An RCD (Residual Current Device) is a common safety device in domestic electrical supplies. It has a small reset button, often red or yellow, and is labelled RCD, RCCB, or RCBO. 

An RCD measures the current in the circuits it controls. If there is an imbalance, it assumes some current has leaked out, causing a danger, and shuts off the power immediately.

RCD (Consumer Unit) FAQ

  • How do I reset an RCD?
    1. Check Lever Position: If the lever is DOWN, the RCD is off.
    2. Reset: Push the lever UP to reset. If needed, push it fully down before pushing it back up. 
  • What if the RCD won't reset?
    1. Switch all fuses (MCBs and RCDs) to the off position excluding the main red switch
    2. Switch on the RCD(s)
    3. Then one by one turn on each fuse (MCB)
    4. Once you attempt to switch the affected fuse back on, this will once again trip out the RCD
    5. Leave the affected fuse switched off, then switch all other fuses (MCBs and RCDs) into the ‘on’ position
    6. You should now have power to all circuits excluding the affected one
    7. If the sockets circuit is the affected circuit, please follow the next set of instructions
  • How to reset an RCD (faulty appliance)
    1. Unplug all appliances from sockets (ensure they are unplugged rather than just switched off as the RCD can still detect a faulty appliance when the socket is switched off)
    2. Ensure all items are unplugged including washing machine, fridge, etc and cooker/shower (only the cooker and shower) switched off at isolation switch
    3. Reset the RCD by switching it back to the ‘on’ position
    4. Plug the accessories back in, one at a time
    5. The RCD may trip again when the faulty appliance that was causing it to trip is plugged back in. Leave this item unplugged and reset the RCD again, it will now stay on
    6. The accessory that is causing the RCD to trip is faulty and will either need to be repaired or replaced
  • How to isolate circuit in the case of water on electrics

    In most circumstances the affected electrical circuit will be the lighting circuit so this is the example used, but this will work for any other circuit e.g. cooker, shower and sockets. 

    • All fuses (MCBs) will be identified. This will be found either written or a picture equivalent underneath the individual fuse
    • Find the affected lighting circuit. This could be split into upstairs and downstairs lighting or could be one lighting circuit for both
    • Switch this fuse into the ‘off’ position – this circuit will now be isolated and de-energised
    • Call RBH to request an electrician visit to check the electrics.