What is the difference between an RCBO and an RCCB?

An RCBO provides protection against both earth leakage and overcurrent (overload/short-circuit). An RCCB only provides protection against earth leakage and must be used with a separate MCB for overcurrent protection.

What are the standard sensitivity ratings (IΔn) for RCBOs?

The standard values are 10, 30, 100, and 300 milliamperes (mA) as per Table 2.

What is the maximum tripping time allowed for a 30mA RCBO?

For a general purpose Type AC RCBO, the maximum break time at its rated residual current (IΔn = 30mA) is 300 milliseconds (ms) according to Table 3.

Is this standard still active?

No, this 1993 version has been superseded by IS 12640-1:2016, which is an adoption of the international standard IEC 61009-1.

IS 12640 Part 2

: 1993

Residual current operated circuit-breakers with integral overcurrent protection for household and similar uses (RCBOs) - Part 1: General rules

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This standard specifies the requirements for residual current operated circuit-breakers with integral overcurrent protection (RCBOs) for household and similar uses. It covers constructional and operational characteristics, standard ratings, and test procedures to verify performance. The primary purpose is to ensure safety against electric shock from earth faults and protection against overloads and short-circuits.

Specifies general rules for residual current operated circuit-breakers with integral overcurrent protection (RCBOs) intended for household and similar installations.

Quick Reference Values

Standard rated residual operating currents (IΔn)10, 30, 100, 300 mA

Max break time at IΔn for general type300 ms

Non-operating residual current0.5 x IΔn

Standard rated short-circuit capacity (Icn)3000, 4500, 6000, 10000 A

Standard rated currents (In)6, 10, 16, 20, 25, 32, 40 A

Practical Notes

An RCBO combines the functions of an RCCB (earth fault protection) and an MCB (overcurrent protection) in a single compact unit, saving space in distribution boards.

Select a 30mA sensitivity (IΔn) for circuits feeding socket outlets to provide direct-contact shock protection. Use 100mA or 300mA for equipment or fire protection on main incoming lines.

The test button ('T') on the RCBO should be operated every six months to ensure the mechanical tripping mechanism is functioning correctly.