Main earth Conductor using Armour

11 Feb 2007
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United Kingdom
Quick Earthing Question

From MET to CU you use 16mm Earth, that is understood.

Today I saw the following:

MET was wired to Earthing teminals of a 100A Switch fuse using 16mm Earth

Switch fuse to CU (located 15m away) was ran in 2 core 16mm SWA cable

The armour of the SWA was then connected to the CU via a banjo and 16mm earth cable to the earth terminal of the DB.

My point is the main earthing from MET to CU is reliant on the armour of the SWA. no separate earth exists.

Your thoughts would be appreciated as to the rights and wrongs of this if any.
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Apart from wondering if the 16mm² is adequately protected, I don't see anything particularly wrong with the setup.
16mm² PVC steel wire armour complies with the requirements for table 54.7 for CPC sizing, 16mm² XPLE doesn't comply with 54.7 for CPC sizing but if you number crunch the adiabatic then you will probably find it is fine.

Some info on sizing of the armour for SWA here (16th edn): //

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