Circuit breakers
Modular circuit breakers provide automatic protection for electrical panel feeders against overloads and short…
A circuit breaker is a modular protective device that automatically interrupts the current in the event of an overload or short circuit in a low-voltage electrical circuit. It differs from a disconnector in its ability to interrupt insulation faults without manual intervention. Modular DIN-rail circuit breakers cover ratings from 1 to 63 A with B, C or D tripping curves, in compliance with IEC 60898-1 and NF C 15-100.
Tripping curves and selection according to the protected load
Curve B, C and D: which tripping curve for which circuit
The choice of tripping curve directly determines the circuit breaker's sensitivity to transient inrush currents. Curve B suits resistive circuits and lighting, where start-up overcurrents remain limited. Curve C is preferred for mixed residential and tertiary circuits with slightly inductive loads. Curve D is required for motor outgoing circuits and equipment with high inrush current. Our installation experience confirms that a poorly matched curve leads to nuisance tripping or, conversely, insufficient protection.
Rating ranges and breaking capacity matched to each installation
Common ratings range from 1 A to 63 A, covering most protection needs for panel outgoing circuits. Breaking capacity varies by range and brand, with values suited to residential, tertiary and industrial contexts. In the field, we find that industrial installations frequently need higher breaking capacities, sometimes supplemented by large-rating circuit breakers outside modular standards.
Available versions and integration into electrical panels
Combined residual current circuit breakers for integrated protection
Some ranges offer combined residual current versions that bring overload, short-circuit and insulation-fault protection together in a single module. This type of residual current circuit breaker reduces panel space and simplifies wiring. Our standard practice favours this solution for wet-room outgoing circuits and outdoor circuits where residual current protection is mandatory under NF C 15-100.
Materials and construction of modular housings
The self-extinguishing polyamide housing provides mechanical strength and resistance to internal electrical arcing. Silver contacts ensure optimum electrical conductivity and endurance to switching operations. Our commissioning tests show that these materials retain their characteristics over the device's rated service life, even in panels subject to thermal variations.
Typical applications and differentiation from neighbouring switching devices
Modular circuit breakers protect panel outgoing circuits in three main areas: individual and multi-occupancy housing, tertiary office and retail premises, and light industrial installations. Unlike the disconnector, which only provides visible isolation and maintenance safety, the circuit breaker provides automatic tripping on fault. This fundamental distinction guides the choice between the two functions in a distribution scheme. Feedback from installers confirms that this confusion remains common in renovation work, where replacing a disconnector with a circuit breaker significantly improves personal safety.
Frequently asked questions
Which tripping curve should be chosen for an LED lighting circuit?
Curve B generally suits LED lighting circuits, as these loads have a low transient inrush current at start-up. A curve C would risk delaying protection in the event of a fault on this type of resistive circuit.
Can a circuit breaker replace a residual current device in a panel?
No, unless it is a combined residual current circuit breaker that integrates both functions. A standard circuit breaker protects against overloads and short circuits but does not detect earth leakage currents.
Which standard applies specifically to modular circuit breakers for buildings?
IEC 60898-1 defines the construction rules, tests and characteristics of circuit breakers for the protection of domestic and similar installations. It is supplemented by NF C 15-100 for application in France.
Why does a single-phase motor require a curve D?
Starting a single-phase motor generates a high inrush current for a few tens of milliseconds. Curve D tolerates this transient without nuisance tripping, whereas curves B or C would break the circuit every time it starts.