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Fully charged Reason for change
Changes to cartridge fuse standards Changes have been made to the British Standards for the cartridge fuse types generally used in electrical installations. These changes, which affect fuses to BS 88 and BS 1361, have been taken into account by Amendment 1 to BS 7671: 2008 (IET Wiring Regulations 17th Edition) and have a number of implications for electrical designers, installers and persons carrying out inspection and testing. Table 1 – Types of fuses affected by the changes
General description of fuse type
Withdrawn standard
Replacement standard (see notes)
Fuses for use by authorised persons (mainly for industrial application)
BS 88-2.2: 1988
BS 88-2: 2010 system E (bolted)
Fuses of compact dimensions for use in 240/415 V a.c. industrial and commercial electrical installations
BS 88-6: 1988
BS 88-2: 2010 system G (clip in)
Fuses for a.c. circuits in domestic and similar premises
BS 1361: 1971(1986)
BS 88-3: 2010 system C
Notes: 1) BS 88-2: 2010 is dual numbered BS HD 60269-2: 2010 2) BS 88-3: 2010 is dual numbered BS HD 60269-3: 2010
Table 2 – Maximum Zs for fuses for industrial/commercial purposes, for 0.4 s disconnection time with U0 of 230 V (see Regulation 411.4.6) Fuses to BS 88-2.2 and BS 88-6 (Both standards withdrawn, and no longer recognised by BS 7671)
Fuses to BS 88-2: 2010 Fuse systems E (bolted) and G (clip in) (Recognised by BS 7671: 2008 (2011))
Rated current (A)
Maximum Zs (ohms)
Rated current (A)
Maximum Zs (ohms)
6
8.52
6
8.21
10
5.11
10
4.89
16
2.70
16
2.56
20
1.77
20
1.77
25
1.44
25
1.35
32
1.04
32
1.04
Note: This table is based on information given in Table 41.2 of BS 7671: 2008 and Table 41.2 of BS 7671: 2008 (2011)
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Winter 2011-12 NICEIC Connections
60_62_technical 5.fuses.FINAL.indd Sec1:60
The changes to British Standards for cartridge fuses are a result of a restructuring and simplification of international standard IEC-60269, Low-voltage fuses, to aid the selection and replacement of such fuses. The technical content of the updated IEC 60269 was used by the European Standardisation body CENELEC to produce a European harmonised document. Consequently the UK was obliged to make the necessary changes to its British Standards for cartridge fuses to maintain technical alignment with the harmonised document. The British Standards that were affected needed to be withdrawn by 1 March 2010 and replaced accordingly. Fuse types and British Standards affected Table 1 lists the types of fuses affected by the changes, together with the numbers of the associated British Standards that have been withdrawn and those that replace them.. Implications for designers, installers and inspectors The changes to the above fuse British Standards have been taken into account in the requirements of BS 7671: 2008 by Amendment 1, which came into effect in January 2012. This has had an effect on a number of the values of maximum of earth fault loop impedance (Zs) for fuses given in Tables 41.2 and 41.4 of BS 7671 for disconnection times of 0.4 s and 5 s at a nominal voltage (U0) of 230 V. Tables 2 to 5 of this article show the changes. Also affected are some values of maximum of Zs for fuses in reduced low voltage systems (U0 of 55 V and U0 of 63.5 V), as given in Table 41.6 of BS 7671. Table 6 of this article shows the changes. The term ‘BS 88 series’ now covers fuses to BS 88-1, -2 and -3. Appendix 1 (list of British Standards) of BS 7671: 2008 (as amended) refers. In the Schedule of Circuit Details accompanying each Electrical Installation Certificate or Electrical Installation Condition Report (or their domestic equivalents, where applicable), the type and rating of any fuses used for overcurrent protection will, as always, need to be accurately recorded. For example, a cartridge fuse recorded as a BS 88-2 would not clearly identify the fuse as a type E (bolted) or a type G (clip-in) device. Therefore, one solution to overcome this would be to insert ‘BS 88-2(E)’ into the data-entry box on the schedule, where the fuse is of the bolted type. The rated currents of some of the fuses in Tables 41.2, 41.4 and 41.6 of BS 7671 have been adjusted. For example, the closest replacement fuse for a 15 A fuse to BS 1361 would be a 16 A fuse to BS 88-3 system C. See the tables
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20/1/12 10:07:31