A residual current circuit breaker (RCCB) is selected on the basis of two numbers and one letter. The rated current is the load the device can carry. The letter is the type, and it determines which shapes of residual current the device can detect. The decisive parameter is the rated residual operating current, written IΔn, which is frequently carried over from a previous project without re-verification.
The CJL1-63 from C&J Electrical sits in the 63 A frame, where most single-phase and small three-phase final circuits land. This article examines what the residual setting controls, where 30 mA is applied and where 300 mA belongs, how AC, A and B types differ, and what else has to be verified.
What the residual setting controls
An RCCB compares the current going out through the live conductor with the current coming back through the neutral. In a healthy circuit the two are equal, so the difference is zero and the device does not operate. When current leaks to earth, through damaged insulation, a wet joint or a person, part of the outgoing current does not return. That difference is the residual current, and when it reaches the set threshold the device opens the live and the neutral conductors.
Nothing about the mechanism is adjustable in service. What is decided at specification time is the threshold: the rated residual operating current, IΔn. On the CJL1-63 it is offered in the fixed steps 10, 30, 100 and 300 mA, and the choice follows the purpose of the circuit rather than the size of the load.
30 mA or 300 mA
These two values are not alternatives to each other. They answer different questions, and a circuit can require both.
Additional protection against electric shock on socket-outlet circuits, wet areas, outdoor circuits and portable equipment.
Higher-level leakage protection for sub-distribution boards and installations whose normal leakage current makes a lower setting impractical.
Protection aimed at reducing the fire risk from a persistent earth fault. Commonly placed at the incoming end of a distribution.
A high-sensitivity setting for special locations or circuits where the design calls for enhanced protection.
Where both a 30 mA and a 300 mA RCCB are installed in the same path, the 30 mA RCCB sits on the final circuit and operates first; the 300 mA RCCB sits upstream and provides back-up and fire-risk protection.
AC type, A type and B type
A higher type does not inherently provide superior protection. The relevant question is what the connected equipment can produce. The CJL1-63 series is available in AC, A and B types, so the same frame and the same dimensions cover both a conventional circuit and one with power electronics.
Poles and rated current
Two further numbers sit alongside the type. The number of poles follows the system: a 2-pole device (1P+N) for a single-phase 230 V circuit, and a 4-pole device (3P+N) for a three-phase 400 V circuit. Neutral switching matters here, because a residual current can flow through a neutral that is still connected, so the device opens the neutral as well as the live conductors.
The rated current is the load the device is designed to carry continuously. On the CJL1-63 it runs from 16 A to 63 A in the usual steps. The rating should be at least equal to the circuit design current, and it has to be coordinated with the upstream overcurrent device on the same busbar.
Functions Not Covered by an RCCB
An RCCB without integral overcurrent protection does not open on overload and does not open on short circuit. It responds to residual current only. It should be noted that an RCCB does not replace earthing, insulation or overcurrent protection; it limits the time a residual current is allowed to flow. On a final circuit it is used together with a miniature circuit breaker (MCB).
Where both functions are wanted in one device, the answer is an RCBO, which adds overload and short-circuit protection to a similar body.
The CJL1-63 series
The CJL1-63 is an RCCB supplied by Zhejiang C&J Electrical Holding Co., Ltd. It is declared to IEC 61008-1 and IEC 61008-2-1, and is offered in 2-pole and 4-pole versions with a rated current from 16 A to 63 A.
Key data of the CJL1-63 series:
| Item | CJL1-63 Specification |
|---|---|
| Type | Residual current circuit breaker (RCCB) |
| Standard | IEC 61008-1 / IEC 61008-2-1 |
| No. of poles | 2P (1P+N) · 4P (3P+N) |
| Rated current In | 16, 20, 25, 32, 40, 50, 63 A |
| Rated voltage Ue | 230 V AC (2P) / 400 V AC (4P), 50/60 Hz |
| Rated residual current IΔn | 10, 30, 100, 300 mA |
| Residual current type | AC type · A type · B type |
| Short-circuit current Inc | 6,000 A |
| Module width | 36 mm (2P) |
| Mounting | 35 mm DIN rail |
| Terminal capacity | up to 25 mm² · 2.5-4 N·m |
| Endurance | 4,000 cycles |
| Housing | flame-retardant PA66 |
Note: Confirm the rated residual operating current, the type, the pole configuration and the rated current against the earthing system, the connected equipment and the applicable installation rules before ordering.
Applications
- Socket-outlet: 30 mA RCCB + MCB
- Wet areas/Outdoor: 30 mA RCCB required
- Sub-distribution: 100 mA or 300 mA RCCB
- Fire-risk: 300 mA at incoming end
- Power electronics: A type or B type
- OEM/Panel-builder: 16A-63A, SKD supply
About C&J Electrical
Zhejiang C&J Electrical Holding Co., Ltd. manufactures low-voltage electrical products, mainly circuit breakers and related protection devices. The company supports OEM brand customization and can ship products as SKD kits for local assembly.
Post time: Oct-15-2026