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

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Requirement for a transient resistance feature < 3 kA and short 10 ms time delay. **Note: Type A transient resistant RCDs only meet EN 61008/9 for general UK 50Hz residual currents. High frequency current components can saturate the RCD, preventing detection of 50Hz residual currents. These are installed to protect circuits where equipment with electronic components are installed such as

Residual Current Devices (RCDs) are safety switching devices. They are designed to provide safety for three types of protection; these are: For single phase inverters used in motor speed control, the characteristics of the equipment will determine if Type A, F or B is required, to meet Regulation 531.3.3 For 3 phase inverters which do not incorporate isolating transformers, Type B RCDs must be used to meet the requirements of Regulation 531.3.3 For additional information. Type AC RCDs are in clause 531.3.3 of BS7671 2018, because they are still in EN 60364-5-53 2015. The UK have just adopted this line from the EN standard.What I would say is look at the article as a whole, as it makes it quite clear that 531.3.3 refers to 4 Types of RCD, and the points to consider when selecting RCDs for circuits containing various items of equipment. It also makes the point about consulting the manufacturer of the equipment for advice. The revised RCD guidance in 531.3.3 is precise. The appropriate Type of RCD must be selected, based on the characteristics of the residual current and the equipment that is likely to be connected to the RCD protected circuit. The initial verification required under 641.1 and 301.1 (ii), covers the requirements for the verification that electrical equipment (any appliance supplied or connected, as part of the existing fixtures and fittings) is compatible with other electrical equipment such as RCDs installed to provide additional protection e.g. for a domestic installation, document the appliance RCD requirements with the justification for the consumer unit specification.

NOTE 1: For RCD Type A, tripping is achieved for residual pulsating direct currents superimposed on a smooth directii) RCD Type A: RCD tripping on alternating sinusoidal residual current and on residual pulsating direct current, suddenly applied or smoothly increasing. 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. Where electric vehicle charging equipment is likely to create a residual DC fault current, manufacturers may provide the correct type of RCD within the charging equipment. However, problems could arise if the charging equipment is installed downstream of an existing Type AC RCD, which could be blinded by the residual DC fault current. In some types of DC charging equipment, the AC input side is galvanically isolated from the DC output which, hence, provides electrical separation. This means that faults on the DC output side, connected to the vehicle, would not be detected by an RCD on the input side of the circuit. What are the hazards and problems? I agree with you on that one, as electricians we have very little control over what will eventually be connected to an installation that we have installed. Type AC RCDs (General Type), which are most commonly installed in dwellings, are designed to be used for alternating sinusoidal residual current to protect equipment which is resistive, capacitive or inductive and without any electronic components.

Domestic properties with modern equipment and appliances, such as LED lighting, induction hobs, IT equipment and electric vehicle charging equipment. The method of installation requires 30mA RCD protection – e.g. Regulation 415.1 & 522.6.202. Dedicated circuit feeding an immersion heater, conventional oven or cooker, with resistance heating elements. You might ask "Why are Type AC RCDs still referred to in the 18th Edition of BS7671, when most installations should be using Type A devices as a minimum requirement?" The term general purpose relating to Type AC devices should not be taken out of context i.e. it is the most basic RCD, suitable for detecting a simple full sine wave residual current at 50Hz. Type AC RCDs subjected to pulsed waveforms will not trip within the safe limits, required for 30mA protection. Appliances containing diodes, produce pulsed residual currents – see Fig 1. Diodes became so common in domestic equipment some years ago, that many countries banned the "general use" of Type AC RCDs e.g. From 1985, VOE Regulations specified the use of Type A RCDs in all domestic installations as a minimum requirement.The method of installation relating to protective earthing will depend on the operational leakage current (protective conductor current) – see 543.7. The use of a 30mA RCD may be required for several reasons; cable installation, location / application area for the pump etc. Take note of 531.3.2 Operational leakage current (protective conductor current) for the circuit should not exceed 30% of the RCD sensitivity.

The fault current (If) contains mixed frequency components between 10Hz (minimum motor frequency) and 1kHz (maximum inverter switching frequency) ***. An RCD monitors the earth leakage current in a circuit. It is constructed from coils of wire wound around a ferrite toroid core, one for each live conductor of the circuit protected. When a current imbalance between live conductors is detected, a voltage will be induced in the tripping coil which will disconnect the electrical supply to the protected circuit (see Figure 1). 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? All types of electrical installations could be affected, it depends on the equipment which has been installed. Examples include:Type A RCDs are not designed to detect smooth dc residual currents. They will still trip within safe limits with < 6 mA smooth dc superimposed on a 50Hz pulsed residual current.