RCD Tripping

Newcastle Electrician

Let’s get started… RCD Help Guide: The 5 steps to fix your RCD.

1. Find out what power outlets / lights are affected. Check the switchboard to ensure that it is actually the RCD that has tripped and not a circuit breaker.

2. UNPLUG ALL affected appliances from socket outlets and if lights are affected by the RCD tripping off, turn off all light switches as well.

Check list: Remember you must “UNPLUG” all appliances like dishwashers, any gas cooktops or hot water units with 240v plug tops for ignition,  outdoor power points etc.

Once that is done, turn on the RCD by firmly pushing the switch up.  You might have to flick it on, off and on again to reset it properly.  Also check that the test button is not stuck in as it will prevent the RCD from resetting.

4. If power and  lights appear to be on,  go about restoring by ‘plugging in and turning on’ to see if there was any particular appliance or light that was tripping your RCD.

5.  If you can not find the problem call the RCD fault specialist Chris on 0403 261 256

RCDs: Newcastle Electrician advise on everything an electrician should know

Electricians do the best they can every day they go to work – and we want to leave a job safer than when we found it. But what if despite our best efforts, we actually made things worse without realising it? In this article, Paul Meenan seeks to answer this question!

Quick history

Historically, two basic types of earth-leakage circuit-breaker (ELCB) were recognised by BS 7671: what we know to be a current-operated type or residual current device (RCD) and the even older voltage-operated type. Today, only the current-operated type is recognised and used.

So, if we look back in time before the 17th Edition came out in 2008 (BS 7671:2008), the 16th Edition and previous editions, the more experienced (older) sparks will remember when ELCB devices were referred to by one of the following terms:

  • protection against indirect contact – now called fault protection
  • supplementary protection against direct contact – now called basic protection
  • protection against fire and thermal effects, and
  • additional protection.

In fact, when we adopted current operated devices (RCDs) to BS 4293, the trip times were much quicker than modern devices, although they may not comply with BS EN standards. BS 4293 was withdrawn in 2000 and manufacturing of these devices should have ceased in 2005. The device was replaced by BS EN 61008.

One of the negatives in using the older mechanical devices were that they could seize up. Modern devices are either electronic or electromagnetic.

What is an RCD?

They are devices installed within an electrical system unit to provide protection to the wiring, fixed appliances and persons using the installation. Protection is achieved by constantly monitoring the electric current flowing through one or more circuits that an RCD is used to protect. If it detects electricity flowing down an unintentional path, such as via a person or faulty appliance down to earth, then the RCD will switch off the circuit very quickly, reducing the risk or death, injury or fire.

Device monitors the ingoing and outgoing current flow and trips when an imbalance occurs.Device monitors the ingoing and outgoing current flow and trips when an imbalance occurs.

The device monitors the ingoing and outgoing current flow and trips when an imbalance occurs as illustrated above.

RCDs are defined by three main characteristics:

  • the rating in amps
  • the rated residual operating current of the protective device in amps, known as the IΔn (pronounced ‘I delta N’), and
  • the instantaneous trip that occurs or an intentional time delay to permit discrimination*. Such devices are called ‘S’ or Special/Selective.

*Note: the term ‘discrimination’ is proposed to be replaced by ‘selectivity’ in the upcoming 18th Edition of BS 7671 (BS 7671:2018).

We find ourselves now using the term ‘RCD’ to cover a range of devices found within an electrical installation. They include:

  • residual current device – RCD found in older devices to BS 4293
  • residual circuit current breakers – RCCB to BS EN 61008
  • residual current breaker with overload – RCBO to BS EN 61009 found in consumer units
  • circuit breaker with RCD fitted – CBR larger industrial application
  • SRCD – socket outlet incorporating an RCD to BS 7288
  • FCURCD – fused spur with RCD integrated, and
  • PRCD – a device that contains a portable RCD within the plug.

As can be seen above, RCDs have merged into other many different products and protective devices although the principles of protection remain the same.

Most domestic electricians use and are familiar with, RCD main switches for circuits or RCBOs in today’s world.

So what’s the concern?

Once we’ve got through the vast array of different manufacturer-branded devices we are left believing we are fully compliant with the regulations! Well, maybe not …

As we all know the MCBs we use come in differing ‘types’– by this, I mean Type B (domestic use), C (commercial installations) or D (industrial large loads). The information on these ‘types’ is found in Appendix 3 of BS 7671 and is formally known as ‘time/current characteristics of overcurrent protective devices’.

That’s first principles I hear you say: I use a Type B or C MCB all the time, I’ll stick with them!

So far so good, we all know this well by now.

However, if you look at Chapter 13 of BS 7671 you will find that it contains copious warnings about external influences on an installation to help you ensure that what you do does not make an installation unsafe or compromised. Regulations 132.5, 132.7, 132.11, 133.3, 133.4 and Appendix 5 are a must-read for any electrician; more importantly, there is no reason not to comply fully with Chapter 13 Fundamental Principles.

Appendix 5 External Influences contains lots of items that can affect an electrical installation.

So, do you think with all the onslaught of modern technology and the drive for smart homes, we are adequately considering and taking all precautions required in terms of our methods of protection?

The issue at hand – what do I need to know?

With all the modern technology that is now installed into domestic installations, would you ever have thought that DC current could be a real issue for you?

Within an installation today it is not rare to find the following:

  • switch mode power supplies – found in all electronic devices to convert AC to DC
  • solar PV panels
  • electric vehicle charging
  • USB socket outlets and
  • smart home and data networks.

All of these have one thing in common: DC current and voltage.

DC has a tendency to leak to earth. When it does, it immediately becomes an AM7 external influence under the categories in Appendix 5. If this does happen, your RCD, in whatever form you use, will NOT perform to the requirements of the standard it is made to. In a nutshell, it becomes less safe –the greater the DC current the bigger the effect.

So what if I told you your RCD was a Type AC or a Type A or F? Confused? Don’t be: there is another use for the term ‘type’– it applies to the RCD device itself and its performance. They are known as Type AC, A, B, F, and more recently a B+ has turned up on the market.

AC: this device ensures tripping for residual AC currents whether sudden or rising; this is standard in most domestic installations. The marking for this is shown below.

A: this device ensures tripping for all types of AC currents and pulsating DC currents that may appear within an installation. The marking for this is shown below.

F: this device ensures tripping for all types of AC currents and pulsating DC currents that may appear within an installation. It also ensures no unwanted tripping and detection of high-frequency faults up to 1KHz. The markings for this are shown below.

B: this device ensures tripping for residual AC currents, pulsating DC currents and smooth DC currents, whether applied suddenly or rising. The markings for this are shown below.

B+: this device ensures tripping for residual AC currents, pulsating DC currents and smooth DC currents, whether applied suddenly or rising. It also ensures no unwanted tripping and detection of high frequency faults up to 20 kHz. The markings for this are shown below.

Hopefully, this article goes a way to addressing questions that you may have had on RCDs or at least set you on a path to gaining a better understanding.