So your electrics have cut out, the lights are off and none of your appliances are working. First thing you check is the consumer unit and you can see the RCD has tripped, how can you restore power?
First it’s important to understand what an RCD is doing for you. An RCD (sometimes labelled as an RCBO or RCCB) is a Residual Current Device which measures amps going down the circuit and compares it to amps returning. If there is more than a difference of 30mA then the RCD recognises that electricity is being lost somewhere and shuts off the supply. This is primarily to protect you from electric shock (30mA being a reasonably survivable shock as opposed to hundreds of Amps).
RCDs usually trip because of a fault in the wiring (or appliances) which causes electricity to leak from the live cables to the earth cable or to some other path to earth (i.e. a human being). This can help us diagnose what might be going wrong, here are some simple steps that most electricians do before further, in-depth, investigation;
1. Did you plug something in when the RCD tripped? Did you start the washing machine or did the fridge kick in? If so, it is more than likely the appliance which is faulty and needs repairing or replacing. Unplug the suspect appliance and reset the RCD, if the power remains on then you can be fairly certain it is the appliance which is causing the tip.
2. Did you turn on a light when the RCD tripped? Sometimes when an old halogen or tungsten bulb fails it can trip an RCD. It’s usually nothing to worry about however if it happens regularly then you may want to have an electrician come around and check the lighting wiring. In this case, switch all the power off at the consumer unit and replace the bulb. If the lighting was to blame, it should now be working.
3. If the RCD tripped out of the blue then you may need to do a little more investigating. Switch off all the circuit breakers except for the main switch and the RCD. Now switch each circuit on in turn until the RCD trips again. At the point the RCD trips you will know which circuit is to blame because it will be the last one you turned on. You have narrowed it down to which circuit, now you can narrow it down further.
4. If the fault occurred on a socket circuit then unplug everything on that circuit and switch all the circuit breakers and RCD on. If the RCD doesn’t trip then plug the appliances back in one by one until it trips and identifies which appliance is to blame. If the RCD trips before plug anything back in then it’s definitely time to call an electrician.
5. If the faulty circuit is a lighting circuit then this can be trickier to identify. It usually means one bulb has blown. Again, if in doubt call an electrician.
6. Sometimes it may be that the RCD itself is to blame. An electrician can run tests through the RCD to see if it is broken or oversensitive. Only a qualified electrician should be testing or replacing an RCD.
As always, if you are in any doubt then call an electrician to investigate and repair the fault. DO NOT remove the front cover to your consumer unit or expose any cables from any of the switches/sockets/lighting points.
For any electrical fault or repairs call Nick on 07526 566 902 or email info@nick-electrician.com. We also offer 24hr emergency call-outs in Bury St Edmunds and surrounding areas.