Proteus 63 AMP 2 POLE 30 mA 2 MODULE RCD 63/2/30T

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All types of electrical installations could be affected, it depends on the equipment which has been installed. Examples include: Assuming an AC Type RCD will suit every installation is incorrect and RCDs shall be selected according to the equipment which is likely to be used within the installation. Type AC RCDs shall only be selected where it can be assured that there is not and will not be any residual DC fault current on the circuit. BS EN 62423:2012+A11:2021 Type F and type B residual current operated circuit-breakers with and without integral overcurrent protection for household and similar uses. The early style Residual Current Devices (RCDs) were highly effective protective devices but they have proven to be less reliable in modern buildings as a consequence of DC leakage and DC fault currents caused by electronic equipment. Subsequently, new types of RCD have been developed.

Residual Current Devices (RCDs) are safety switching devices. They are designed to provide safety for three types of protection; these are: NOTE 1: For RCD Type A, tripping is achieved for residual pulsating direct currents superimposed on a smooth direct Table 4 Maximum values of break time for Type A RCD extracted from BS EN 61008-1:2012+A2:23-1:2012+A11:2015 A Type S RCD is a sinusoidal residual current device incorporating a time delay. It can be installed upstream from a Type AC RCD to provide selectivity. A time-delayed RCD cannot be used for additional protection because it will not operate within the required time of 40 mS. RCDs work by monitoring the flow of current in a circuit's live conductors and, if the flow of current is imbalanced due to an earth leakage current of a set nominal value, the device will trip to cut off the supply to the circuit. Whilst RCDs have a nominal tripping current (IΔn), they may trip below the nominal value; for instance, a 30 mA RCD is required to trip at a current between 18 mA to 28 mA.

NOTE 4: For guidance on the correct use of RCDs for household and similar use, see PD IEC/TR 62350. In new installations, it is common practice to install a consumer unit which was supplied with RCDs already connected. These are likely to be Type AC which could be ineffective due to the residual DC fault current created by types of electrical equipment. Many installers, either because of habit or a misunderstanding of the limitations for an AC Type RCD, often assume they are suitable for all installations, but this is incorrect.

It was noted that those testing RCDs in the field would find it difficult to carry out the variety of tests permitted and may not know which of the available tests would be applicable to a given make or type of RCD. There is no longer a requirement to perform a test using a test current equal to or higher than five times the rated residual current. What is an alternating current test?For those that decide to continue to carry out all of the tests previously required, it is important to consider what the benefits really are and if the lifespan of the RCD be reduced, possibly to the point where it may not work when required. RCD testing issues Modern appliances are becoming increasingly more sophisticated, featuring microprocessor technology with an emphasis on energy reduction. This has led manufacturers to incorporate energy-saving measures, such as speed control, which by the nature of its operation has an element of DC residual fault current. Which types of installation could be affected? Further information on RCD operating and non-operating times can be found in the relevant product standards. Type A and Type AC RCCBs and RCBOs are manufactured to BS EN 61008 and BS EN 61009 respectively, whereas Type F and Type B RCCBs and RCBOs are manufactured to BS EN 62423.

NOTE 5: Some typical fault currents in circuits comprising semiconductors are given in Annex A53, Figure A53.1.” What are the effects of DC residual fault current on RCDs?

The requirements for testing RCDs have been simplified, a single test is all that is required to show compliance with the minimum requirement laid out in BS 7671:2018+A2:2022. Regardless of RCD type, the test is carried out using an alternating test current, applied at the RCD’s rated residual operating current I Δn, the maximum disconnection time is expected to be less than 300ms for a general non-delay type RCD. For S type time-delayed RCDs, the operating time should be 130 - 500 ms. Other kinds of RCD testing may be useful for fault finding purposes. NOTE 3: For RCD Type B, tripping is achieved for residual pulsating direct currents superimposed on a smooth direct current up to 0.4 times the rated residual current (IΔn) or 10 mA, whichever is the highest value.

The advent of new technologies has created different challenges for the electrical designer and installer. Some modern equipment can create DC residual fault current. Such items include, variable-speed drives, LED lighting, washing machines, dishwashers and tumble dryers.

Residual Current Device is a generic term used for describing devices which incorporate residual current protection in accordance with one of the standards below: In existing electrical installations, Type AC RCDs have been installed for many years and are effective for equipment which is resistive, capacitive or inductive and fitted with minimal electronic components. This used to be the case for most installations when lighting was of the tungsten type, and the electrical appliances or equipment did not contain any electronic equipment. In a healthy circuit, the vector sum of the currents flowing in all live conductors should be nominally zero. When a fault occurs on a circuit causing a current to flow to earth, this creates an imbalance and trips the device. What is DC residual/fault current? Recently introduced in the BS 7671:2018, Regulation 531.3.3 states that different types of RCD exist and the appropriate type shall be selected according to the connected equipment. For further information on the different RCD Types and the selection process, see IET Wiring Matters article (Issue 77 September 2019), ‘Which RCD Type?’