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Wednesday, 12 December 2012

IET Code of Practice - some useful advice

There has been much criticism of the latest edition of the Code of Practice recently including on this blog. However trawling through Edition 4, I came across some useful information that throws some light on an issue that has been puzzling me for some time. This is to do with cable rating and fuses.

The prime purpose of the fuse in the plug is to protect the cable attached to the appliance. For example, where the cable rating is 6 Amp, we need to make sure that the fuse fitted is either 3 Amp ar 5 Amp. Clearly a 13 Amp fuse is not going to protect this cable.

Having said this, my colleagues and I have come across a number of appliances where the fuse in the plug is 13 Amp, but the cable is only rated at 10 Amp or sometimes only 6 Amp. The marking on the cable on a travel kettle that was purchased recently had 3 x 0.75 marked on it, indicating that it had 3 conductors, each of 6 Amp current carrying capacity.  This was a newly purchased appliance and not one where the cable had been changed by someone.

This has puzzled me as I wasn't sure how such an appliance could have meet the Low Voltage Directive.

In Edition 4, Note 2 regarding Table 6.1 says "Where a manufacturers' flex is less than 2 m in length, has a csa of 0.75 mm2 and is fitted with a non-rewirable plug, it may be rated at 10A and be fused to 13A, in accordance with BS 1363 Table 2 Note C.

In summary, this is a very useful bit of information that helped to clear a mystery for me. If I find any more useful practical information like this in Edition 4 of the COP, I will post this on this blog.

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