What is the difference between an RCCB and an MCB?

An RCCB protects against earth leakage current (shock hazard), while an MCB protects against overcurrent (overload and short-circuit). They serve different safety functions.

Which RCCB rating should be used for human safety?

A high-sensitivity RCCB with a rated residual operating current (IΔn) of 30 mA or 10 mA is required for protection against direct contact and electric shock.

Does this standard cover RCCBs with built-in overload protection?

No, this standard is for RCCBs only. Devices with combined residual current and overcurrent protection (RCBOs) are covered by IS 12640.

What is the maximum tripping time for a standard 30mA RCCB?

For a general type RCCB, the maximum break time at its rated tripping current (30mA) is 300 milliseconds (0.3 seconds) as per Table 3.

IS 13947 Part 1

: 1993

Residual current operated circuit-breakers without integral overcurrent protection for household and similar uses (RCCBs) - Part 1: General rules

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This standard covers the general rules and specifications for Residual Current operated Circuit-Breakers (RCCBs) that do not have integral overcurrent protection. It applies to devices for household and similar uses, detailing their classification, operational characteristics, construction, and testing methods to ensure user safety from electric shock.

Specifies general rules for residual current operated circuit-breakers intended for household and similar installations, without integral overcurrent protection (RCCBs).

Quick Reference Values

Human safety sensitivity rating30 mA

Max break time for general type at IΔn300 ms

Minimum insulation resistance2 MΩ

Insulation resistance test voltage500 V DC

Standard dielectric test voltage (for 240/415V systems)2000 V AC

Standard rated currents (In)16, 25, 40, 63 A

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

Practical Notes

A common mistake is assuming an RCCB also protects against overloads or short circuits. This is incorrect; an RCCB only detects earth leakage and must be backed up by an MCB or fuse for overcurrent protection.

The test button ('T') on an RCCB should be operated monthly by the user to ensure the mechanical tripping mechanism is working correctly.

For personnel protection (e.g., in socket circuits, bathrooms), an RCCB with a sensitivity of 30 mA or less is mandatory.