Residual current circuit breakers (RCCB): Which type is suitable for our electrical installation - type AC, type A or type F ?

28.09.2021

It often happens that when looking at the product catalog of a large manufacturer of electrical equipment, we get lost in the variety of products and the accompanying specifications. No matter how good we are in a given field, the constant development of technology, changes in standards and requirements in the implementation of electrical installations… keep us alert.

One of the common questions when building the electrical installation of a building - residential, office, warehouse… is the choice of the appropriate type of residual current circuit breakers.

The RCCB measure the difference in current intensity between the phase and neutral conductors. Therefore, if there is a leakage current that can damage the human body, the RCCB operates within a few milliseconds and prevents damage. In accordance with the wiring requirements of the international standard IEC 60364, a RCCB must be provided with an operating leakage current lower than 30mA, in the following cases:

  • for contact outputs with rated current lower than 32A, regardless of their location - in corridor, bedroom, office, etc.
  • for all electrical circuits in wet rooms - bathrooms, laundry rooms, swimming pools…
  • in the case of mobile equipment for outdoor use which has a rated current lower than 32A - caravans, campers, temporary structures…
  • for lighting circuits in individual homes with TT and TN (TN-C or TN-S) earthing systems (TT - there is independent earthing in the building, there is no connection between earth and zero; TN-C - zero is earthed in the building or TN -S - the ground is zero at the transformer);
  • for supply chains on work sites, recreational craft, traveling fairs…

What are the types of residual current circuit breakers and in what cases are installed?

There are three types of residual current devices - type AC, type A and type F:

RCCB type AC is designed to detect residual sinusoidal currents:

  • incandescent lighting fixtures, electric heaters and water heaters;
  • microwave ovens and small household electrical applications
LDG ltd

In some cases, the expected fault current may contain a pulsating form of direct current. This is due to the fact that the fault current flows through a rectifier. In these cases we should use RCCB type A:

  • computers and circuits in which devices with switching power supplies can be connected;
  • induction hobs, washing machines, dryers;
  • machines with nonlinear elements (diodes, capacitors, rectifiers) - motors, production machines and photovoltaics 1P.
LDG ltd

The operation of the fault current protection may be affected by certain electrical and electromagnetic interference (e.g. lightning). This can lead to a "wrong shutdown". Type F RCCB is recommended in the following cases:

  • for loads generating high frequency interference - air conditioners, powerful IT equipment, pumps and motors with frequency regulator;
  • for critical loads requiring continuity of work - IT halls, hospitals, refrigeration rooms, etc.
  • in electromagnetic media - with increased risk of lightning, redundant networks or at risk of transient currents, etc.
LDG ltd

You can see the fault current protections offered by us at LDG on our website here:

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