This standard applies to a.c. air-break circuit-breakers for operation at 50 Hz or 60 Hz, having a rated voltage not exceeding 440 V (between phases), a rated current not exceeding 125 A and a rated short-circuit capacity not exceeding 25 000 A. As far as possible, it is in line with the requirements contained in IEC 947-2.These circuit-breakers are intended for the protection against overcurrents of wiring installations of buildings and similar applications; they are designed for use by uninstructed people and for not being maintained.This standard also applies to circuit-breakers having more than one rated current, provided that the means for changing from one discrete rating to another is not accessible in normal service and that the rating cannot be changed without the use of a tool.This standard does not apply to:- circuit-breakers intended to protect motors,- circuit-breakers, the current setting of which is adjustable by means accessible to the user.For circuit-breakers having a degree of protection higher than IP20 according to IEC 529, for use in locations where arduous environmental conditions prevail (e.g. excessive humidity, heat or cold or deposition of dust) and in hazardous locations (e.g. where explosions are liable to occur) special constructions may be required.Requirements for circuit-breakers which incorporate residual current tripping devices are to be found in IEC 1009-1, IEC 1009-2-1, and IEC 1009-2-2.A guide for coordination of circuit-breakers with fuses is given in annex D.NOTES1 Circuit-breakers within the scope of this standard are considered as suitable for isolation (see 8.1.3).Special installation precautions (e.g. use of adequate lightning arresters) may be necessary when excessive overvoltages are likely to occur on the supply side (e.g. in the case of supply through overhead lines).2 Circuit-breakers within the scope of this standard may also be used for protection against electric shock, in case of a fault, depending on their tripping characteristics and on the characteristics of the installation.3 The criterion of application for such purposes is dealt with by installation rules.