MICC Cable Outer Sheath

[Seanw]

Hello,

Under the 17th Edition are you still allowed to use the outer sheath as earth ?

 

[telectrix]

as faras i know, yes, as long as its of sufficient Xsectional area to carry the calculated fault current.

 

[glynnis]

Hello,

Under the 17th Edition are you still allowed to use the outer sheath as earth ?

It's MICC, the outer sheath IS the earth! you cant isolate it from earth due to how it's terminated.

 

[telectrix]

agreed, but i think the op was concerned if you had to have an earth conductor in the cable as well. i've not used micc for years, it always was that the skin was earth then.

 

[IQ Electrical]

It's MICC, the outer sheath IS the earth! you cant isolate it from earth due to how it's terminated.

Yes, as Telectrix said, the OP was checking on the suitability of the sheath as a CPC.

The sheath is very good as a cpc but not always so if also a combined protective bonding conductor,

Table D11 in Guidance Note 1 has 'effective sheath CSA' values for many commonly available MICC types.
2L2.5 for example has a sheath equivalent of 8.2mm.

 

[ian.settle1]

Yes, as Telectrix said, the OP was checking on the suitability of the sheath as a CPC.

The sheath is very good as a cpc but not always so if also a combined protective bonding conductor,

Table D11 in Guidance Note 1 has 'effective sheath CSA' values for many commonly available MICC types.
2L2.5 for example has a sheath equivalent of 8.2mm.

Have seen a chart somewhre which gives the CSA of the sheath similar to the SWA chart

 

[Seanw]

thanks for the quick replies , i only ask as we have to install a 4mm 2C MICC cable and the spec calls for the earth to be used as the shealth. The pm says

Yes I believe that is why we are using 3 core this should be what has been priced because I don’t think 17th edition allows the sheath to be used but may be wrong.

 

[IQ Electrical]

You're welcome Seanw but remember the 'thanks button'

 

[ian.settle1]

thanks for the quick replies , i only ask as we have to install a 4mm 2C MICC cable and the spec calls for the earth to be used as the shealth. The pm says

Don't you mean the sheath is to be used as the earth

 

[Seanw]

yes the spec says earth used as sheath , but he says we need a 3C to use 1 C as earth because the 17th edition does not allow you to use the sheath as earth

Is this correct ?

 

[IQ Electrical]

'He' needs to read BS7671:2008 of course you can use the sheath, I posted the detail of the reference material supporting this!

 

[Guest123]

Physical cross sectional area of MICC/PYRO copper sheath for use as CPC.


2L1 ****** 5.4 mm2
3L1 ****** 6.7mm2

2L1.5 ****** 6.3 mm2
3L1.5 ****** 7.8 mm2
4L1.5 ****** 9.1 mm2


2H1.5 ****** 11 mm2
3H1.5 ****** 12 mm2
4H1.5 ****** 14 mm2


2L2.5 ****** 8.2 mm2
3L2.5 ****** 9.5 mm2
4L2.5 ****** 11 mm2

2H2.5 ****** 13 mm2
3H2.5 ****** 14 mm2
4H2.5 ****** 16 mm2

2L4 ****** 11 mm2
2H4 ****** 16 mm2

2H6 ****** 18 mm2
3H6 ****** 20 mm2

2H10 ****** 24mm2
3H10 ****** 27mm2

2H16 ****** 30mm2
3H16 ****** 34mm2

 

[nick611]

no its not correct,earth sheath is fine as cpc in micc cable

 

[nickblake]

cant use the sheaath as an earth what a numpty the pots come with the earth lead attached and look at lennys post ,how often do you see crossectional earths as good as that not in many twin and earths , 4mm twe 2.5mm cpc 4mm micc 11mm earth i rest my case

 

[murdock1971]

as far as im aware you can use the outer sheath of the cable as long as you use an earth tail pot and not a standard one

 

[IQ Electrical]

as far as im aware you can use the outer sheath of the cable as long as you use an earth tail pot and not a standard one

Absolutely not true, earth pots were introduced for applications where glands were not used but a cpc connection was still required.

Conversely, good cpc continuity can still be achieved with a gland and standard pot.

 

[nickblake]

Absolutely not true, earth pots were introduced for applications where glands were not used but a cpc connection was still required.

Conversely, good cpc continuity can still be achieved with a gland and standard pot.

Spot on ,

 

[Engineer54]

It strikes me, that today's electricians are getting absolutly no training in MICC cables or in it's installation.
Yet install an installation in MICC today, ....and it will last forever, unlike any other form of wiring. Next they'll be calling it a ''speacialist'' wiring system!!! How times change, and as usual money is at the route cause of it!!

 

[Dave_]

It strikes me, that today's electricians are getting absolutly no training in MICC cables or in it's installation.
Yet install an installation in MICC today, ....and it will last forever, unlike any other form of wiring. Next they'll be calling it a ''speacialist'' wiring system!!! How times change, and as usual money is at the route cause of it!!

Couldn't agree with you more! Its a shame we live in such an expensive world.....