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You've lost power? Maybe the RCD has tripped?

“I've lost half the power to the house, can anyone recommend an electrician?”....... Sound familiar?

So you've lost power to a circuit, half the property or all the property? It sounds like the RCD may have tripped.

What is a RCD?

A RCD (Residual Current Device) is a device that operates by detecting an imbalance between the live and neutral conductors.

When a circuit is healthy, i.e it has no faults, the current flowing in and out of the RCD will be equal. When a fault develops, some of the current will be diverted down the CPC- (Circuit Protective Conductor) or earth causing an imbalance in the live and neutral which will cause the RCD to trip.

How to find your RCD if it has tripped

The RCD shown will be in the consumer unit, and will also have around 8-10 MCBs (Miniature Circuit Breakers) beside it.

Dual rcd consumer unit
Hager dual RCD consumer unit with labels

Alternatively, some consumer units have combined RCDs & MCBs called RCBOs. See the picture below which highlights the difference.

Rcbo consumer unit
Hager RCBO consumer unit with labels

A faulty circuit can be identified by:
  1. Switching off the RCD (usually to the down position, depending on manufacturer).

  2. Switch off all MCB’s

  3. Now one by one reset the MCB’s leaving a few seconds in-between each circuit. When you get to the faulty circuit the RCD will operate (trip).

  4. Once the faulty circuit has been identified, switch off that MCB

  5. Reset the RCD so it’s in the on position (up), this time switch each MCB back on one at a time but skip the circuit that caused the trip last time.

  6. Majority of the power to the house should now be restored.

General MCB sizing

50/45/40 amp will be for cookers, hobs, electric showers or a sub main feed to home offices, sheds, summer houses

32 amp will be for sockets around your home or a sub main feed to a garage or shed, but can also be for cookers, hobs or hot tubs.

20 amp or 16 amp will be for just a few sockets around your home or possibly a feed to a garage, water heaters or electric fires.

10 amp or 6 amp will be for lighting.

This is probably the most common reason we get called out to an RCD tripping:

You have a faulty appliance plugged into a socket circuit. Usually a 16amp, 20amp, 32amp MCB.

A faulty appliance can be tracked down by unplugging all appliances (make sure you unplug the appliance and not just switch the socket switches off).

Once all the appliances are unplugged try to reset the RCD, if it now resets and stays in the upright/on position start plugging appliances back in one by one until the RCD trips again, when the rcd trips it will highlight the faulty appliance.

Common causes are dishwashers, irons, kettles and fridges.

Fridges/freezers can be a bit problematic to identify because the fault may only happen when the motor kicks in and you may not be aware of when that is happening. An appliance engineer would confirm this type of fault.

Lighting circuit fault

You have a faulty light on a lighting circuit (usually a 6 or 10amp MCB).

A faulty light fitting can be identified by;

With the MCB - DOWN / OFF, go around the property, and switch all the light switches in the opposite position.

Reset your RCD, should the RCD work, go around your property switching on all the lights, if the RCD trips when a certain switch is operated that light/lights have a problem.

The RCD trips sporadically?

Water ingress- maybe the outside lights have failed, outside socket letting water in, leaking water pipes, roof issues

Damaged cables- cables screwed through/pinched, DIY gone wrong.

Rodent damage- vermin chewed through the insulation of the cables in the loft, wall, or under suspended floors

Loose connections- incorrectly terminated wiring accessories or junction boxes

Thermal/Fire damage- cables have melted due to the wrong type of cables used or incorrectly installed.

Again this can prove problematic to identify & requires specialist test equipment so you will need to contact an electrician.


If you have to call out an electrician for help

To save time, and to save YOU money, explain what happened.

  • When did it happen?

  • What were you doing?

  • What appliances did you have on?

  • Is there a loose socket?

  • Have you had someone carry out some DIY – such as putting up shelves, or hanging a picture?

  • New carpets- have loose floorboards been screwed down?

  • Have you heard mice around your floors or even in the attic?

  • What time of day?

  • What was the weather like?

Based on the points above, tell the electrician EVERYTHING however insignificant you think it could be as this will help the electrician to trace the fault quicker and resolve the problem sooner.

With over 20 years of experiance Eclipse Electrical can help with your issues. We can identify the issue quickly and get you back up and running in no time

Or call us on 01926 354690

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