RCD Types
IEC 60755:2017 classifies RCDs are classified into four types according to their operation in response the presence of DC components and frequencies other than the rated frequency.
Classification according to the presence of DC components and frequencies other than the rated frequency
Cl. 5, Section 10, Part 1, SP 30:2023 describes the four type of residual current devices and their applications with resect to their operation in response the presence of DC components and frequencies other than the rated frequency:
Type AC: Detection of AC residual currents at the mains frequency as per product standards IS 12640-1 (IEC 61008-1), 12640-2 (IEC 61009-1). BANNED IN SEVERAL COUNTRIES.
Type A: Detection of AC residual currents and pulsating DC residual currents at the mains frequency; correct tripping is only guaranteed at 50 Hz – residual current, as per product standards IS 12640-1(IEC 61008-1), 12640-2(IEC 61009-1).
Type F: Detection of AC residual currents and pulsating DC residual currents at the mains frequency and AC residual currents with multiple frequency components; main component is always 50 Hz, as per product standard IEC 62423​
Type B: Detection of AC residual currents and pulsating DC residual currents at the mains frequency, as well as smooth DC residual currents and AC residual currents ≠ mains frequency as per product standard IEC 62423, IS/IEC 60947-2
Applications of Type A RCDs:
Clause 5.2, Section 10, Part 1, SP 30:2023
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Type A RCDs shall be used where the application may create pulsating DC residual current or smooth DC residual current upto 6mA.
Tripping is ensured:
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—for residual pulsating direct currents, and
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—for residual pulsating direct currents superimposed on a smooth direct current of 6mA,
​with or without phase-angle control, independent of polarity, whether suddenly applied or slowly rising.
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Example Applications: Socket-outlets, Dimmers, Lighting
Limitations of Type A RCDs
Annex G, IEC 60364-5-53:2019+AMD1:2020
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—Cannot protect where smooth DC residual currents exceed 6mA (e.g. electrical vehicle supply equipment)
—Cannot protect where composite residual currents may exist (e.g. single-phase variable frequency drives)
—Cannot protect where residual sinusoidal alternating currents up to 1000 Hz may exist (e.g. multi-phase variable frequency drives)
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Because type A RCDs can only protect applications where smooth DC residual currents do not exceed 6mA, they are permitted for socket-outlets (not intended for the connection of inverter driven appliances) because IEC 61140:2016 requires pluggable electrical equipment with a rated input ≤ 4kVA have a maximum smooth superimposed d.c. current component of 6mA.
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If socket-outlets are intended for the connection of single-phase inverter driven appliances, such as washing machines, drills, dishwashers etc., type A RCDs cannot be used, as these appliances create composite residual currents, in the presence of which type A RCDs cannot reliably trip.
Applications of Type F RCDs:
Clause 5.3, Section 10, Part 1, SP 30:2023
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Type F RCDs shall be used for circuits where there is a risk of residual current containing DC components and chopping frequency currents.
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Tripping is ensured:
—as for Type A
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—for composite residual currents which may result from circuits supplied between phase and neutral or phase and earthed middle conductor, as given in IEC 60755:2017, and
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—for residual pulsating direct currents superimposed on smooth direct current of 10mA.
The above specified residual currents may be suddenly applied or slowly rising.
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Example Applications: single-phase inverter driven loads such as washing machines, dishwashers, vacuum cleaners, drills, air conditioners, etc.
Limitations of Type F RCDs
Annex G, IEC 60364-5-53:2019+AMD1:2020
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—Cannot protect where smooth DC residual currents exceed 10mA (e.g. electrical vehicle supply equipment)
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—Cannot protect where residual sinusoidal alternating currents up to 1000 Hz may exist (e.g. multi-phase variable frequency drives)
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Is not suitable for three-phase inverter driven loads such as 3-phase air conditioners, 3-phase variable frequency drives etc.
Applications of Type B RCDs:
Clause 5.4, Section 10, Part 1, SP 30:2023
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Type B RCDs shall be used where there is a risk of DC residual current, residual current containing frequencies higher than 50 Hz
—for residual direct currents which may result from rectifying circuits, i.e.
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—two-pulse bridge connection line to line for two- three- and four-pole devices;
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—three-pulse star connection or six-pulse bridge connection for three- and four-pole devices;
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— for residual smooth direct currents.
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The above specified residual currents may be suddenly applied or slowly increased independently of polarity.
Type B RCCBs are suitable for all applications. We have ready stock of Type B RCDs. Please click here to see our range of Type B RCDs.
Doepke Type B RCD Offering
Doepke produces a variety of type B RCDs. We have ready stock of type B 30mA & 300mA versions. Click here to see our full type B offering.
2P 63A 30mA Type B
4P 40 A 30mA Type B
4P 40A 300mA Type B