Spanish Regulation will soon evolve and will ask for type A RCD to be used for the protection of all circuits requiring RCD protection.
Until this revision of the Spanish Administration, the local regulation did not prescribe the type of RCD to be used.
This new decision generalizes the use of type A RCDs.
Why and where type A RCDs?
Type A RCD fits the need of protection of circuits containing common loads or loads including rectifiers powered by single phase supply (e.g. power supplies, chargers).
Type A RCD ensures protection in the event of an insulation failure or an hazardous leakage current for residual current waveforms:
- of pure AC residual current as does an RCD of type AC.
- additionally type A RCD also trips on residual currents with the shape of a half wave rectified current and which may contain a maximum of 6mA of DC component (see Fig. 1).
Type A RCD symbol as marked on the device:
The type and sensitivity of an RCD must be adapted to the needs of the circuit to be protected, and the loads connected.
A non-exhaustive list of loads for which type A is suitable is: general purpose power sockets, lighting circuits (incandescent, LED, dimmers etc.), class II consumer electronics (hair dryer, TV, flat screens, etc.), electric heater, water heater, class I domestic appliances (induction cooking, electric cooking plates, etc.), single phase UPS or single phase photovoltaic systems with DC component less than 6mA, single-phase machines with diodes, capacitors and rectifiers, machine tools, EV charging circuit with DC component less than 6mA.
Type A RCD is not suitable for installations where DC components superior to 6mA may circulate (typically 3 phase installation with power converters, PV systems with battery or EV charging spots with no declaration regarding the DC component of less than 6mA) nor for applications where mixed frequencies may be generated and seen by the RCD.
Some applications may require high level of service continuity, in this case SE type A-SI RCD are the solution.
Sites exposed to thunderstorms, circuits with single phase power converters, single phase UPS, circuits or site exposed to switching transients are experiencing harsher environment in terms of transient events (also called electromagnetic perturbations). We strongly recommend the use of super immunized (SI) RCD, type A-SI as it is our most suitable device for improving service continuity.
Get the RCD guide.
About the author
Maria Vallet, Senior Application Architect
Maria received a Ph.D. degree in electrical engineering from the Grenoble Institute of Technology, France, in 2009. After a two-year adventure in a startup developing low power wind turbine generation systems, she joined Schneider Electric in 2011. Since then, she worked in several technical roles related to the electrical distribution applications and protection. Currently, she is working as an expert in Electrical Distribution Applications and protection with RCDs in the Energy Management division of Schneider Electric.
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