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

Product Information

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 Some equipment will have DC leakage current by the nature of design, other equipment may produce DC currents during fault conditions, dictated by the construction of the equipment.

RCDs are far more sensitive than circuit-breakers. The sensitivity being rated in milliamps (mA) as opposed to amps (A). Different Types of RCDIn 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? Type A RCDs are used for alternating sinusoidal residual current and for residual pulsating direct current up to 6 mA. Appliances used in domestic, agricultural and commercial premises, including certain types of washing machine, induction hobs, LED lighting, pumps etc. can produce residual currents that are not compatible with type AC RCDs. The general safety guidance given in the 17th Edition for RCDs, is no longer appropriate for many appliances and loads connected in these installations. Consequently the 18th Edition Wiring Regulations have been updated to align with the existing Electrical Safety Standards already adopted in other countries.

Residual Current Circuit-Breaker (RCCB) without protection against overload BS EN 61008, BS 4293, BS EN 62423. In the UK, residual current protection has been installed with little consideration for the nature of appliances and loads connected downstream of the RCD, this can affect the operation of the RCD.NOTE 4: For guidance on the correct use of RCDs for household and similar use, see PD IEC/TR 62350. e) for residual smooth direct currents, whether suddenly applied or slowly increased, independent of Fault Protection. Any tripping current dependent on the resistance of the earth path. (Regulations 411.4.204; 411.5.1; 531.2). It should be noted that the residual DC leakage current can vary with motor speed and cable length.

ii) RCD Type A: RCD tripping on alternating sinusoidal residual current and on residual pulsating direct current, suddenly applied or smoothly increasing. Residual Current: A fault current that flows to earth, due to an insulation failure within an electrical installation i.e. the difference between the current flowing into and out of system via the live conductors. 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. Industrial installations using uninterruptible power supplies (UPS) and variable speed drive (VSD) frequency inverters for the speed control of motors. 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.There are many different RCD types available, each being suitable for different equipment types, as identified in Regulation 531.3.3 of BS 7671:2018. 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. Temporary installations for structures, amusement devices and booths at fairgrounds, amusement parks and circuses, and