MK Sentry RCD 100A 30MA 230V DP Type A 2 Module

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Domestic properties with modern equipment and appliances, such as LED lighting, induction hobs, IT equipment and electric vehicle charging equipment. Residual Current Circuit-Breaker (RCCB) without protection against overload BS EN 61008, BS 4293, BS EN 62423.

Industrial installations using uninterruptible power supplies (UPS) and variable speed drive (VSD) frequency inverters for the speed control of motors. The RCD type should not be confused with the different types of circuit-breakers which are manufactured according to their time/current characteristics. Circuit-breakers for overcurrent protection of cables are available in types B, C and D in accordance with BSEN 60898-1. It's quite easy to see how an RCBO with a B Type time-current curve could be mistaken for a Type B RCD. Solar photovoltaic systems incorporate inverters to convert DC to AC for use either within the electrical installation or to be supplied to the National Grid. Some inverters may provide galvanic or electrical separation between the AC mains supply and the DC side of the PV array. Where this is not the case, some manufacturer’s instructions state that Type B RCDs to BS EN 62423 must be used. 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.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? NOTE 1: For RCD Type A, tripping is achieved for residual pulsating direct currents superimposed on a smooth direct 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.

These devices have extended tripping times and a transient resistant feature as standard. For reasons of safety, 30mA devices cannot be supplied with time delay characteristics. Earth Leakage Current (Protective Conductor Current): Electrical appliances, connections and cables allow some current to leak to earth, due to internal or natural capacitance associated with the installation. This current should travel to earth via the PE (protective earth) conductor. If the PE conductor is disconnected or faulty (high resistance), a person touching uninsulated parts of the equipment would be subject to the leakage current, that normally flows through the PE conductor. The regulations set limits for protective conductor currents and methods for connecting the protective conductor to the equipment – see 543.7 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. 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.

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.