Protection for >3m tails

[SJD]

I'm familiar with current regulations for protection of meter tails over a certain (e.g. 3m) length, but what about a periodic inspection of a fairly old installation?

The installation in question has a Henley block, then an old isolator - looks to be perhaps 40+ years old, with no fuse - feeding a distribution board in a remote part of the house (in addition to an old fuse board close by the meter, also from the Henley block). The isolator looks in good condition otherwise. The distribution circuit is 10mm2 twin & earth, and maybe 15m or so long.

If this was acceptable practice at the time, does it need more than a C3 code now on an EICR for missing protection of long tails?

 

[telectrix]

could be a potential danger if 10mm tails are protected only by the DNO fuse of 80A or 100A, in which case it's a code C2. if the tails show no sign of overheating, then you might give it a C3. your call, mate. personally, i'd quote for a 50A fused (or MCB) isolator. they're not a huge cost.

 

[SJD]

Thanks Tel. Actually I don't know the fuse size in the DNOs fuse carrier, and will only find out later, if I end up replacing the isolator (or the other fuse board). However, your post made me realize that because the tails are only 10mm T&E, probably it needs a C2 for that anyway with the mix of installation methods applicable. I'd still be interested in comments that suppose if the tails were larger, e.g. 16mm T&E clipped direct with an 80A DNO fuse, was that once OK and thus only need a C3?

 

[telectrix]

suppose if the tails were larger, e.g. 16mm T&E clipped direct with an 80A DNO fuse, was that once OK and thus only need a C3?



AGREE.

 

[Flanders]

Re: Protection for >3m tails

Due to the fuse board being remote there should be a local fuse adjacent the Henley Block anyway but due to size of cable I would C2 it and also add no RCD protection on cable as a C3

- - - Updated - - -

Due to the fuse board being remote there should be a local fuse adjacent the Henley Block anyway but due to size of cable I would C2 it and also add no RCD protection on cable as a C3

 

[telectrix]

it's a C2 and 1/2, IMO. LOL.

 

[Guest55]

i thought the max length of tails was a dno , therefore an ESQCR , regulation.
you could argue it falls out of the remit of a inspection to bs7671.
if all other aspects of the tails are ok ( correct size , adequately supported / protected )
exactly which reg do you code against ?
mention it in the report , but without code.

 

[telectrix]

i thought the max length of tails was a dno , therefore an ESQCR , regulation.
you could argue it falls out of the remit of a inspection to bs7671.
if all other aspects of the tails are ok ( correct size , adequately supported / protected )
exactly which reg do you code against ?
mention it in the report , but without code.

i agree up to a point, as regards the DNO and ESQCR comment, but you still have 10mm tails protected by an over sized fuse, which, IMO, warrants a code, even if only a C3,

 

[Guest55]

i agree up to a point, as regards the DNO and ESQCR comment, but you still have 10mm tails protected by an over sized fuse, which, IMO, warrants a code, even if only a C3,

good call , didnt notice the tails only 10mm , my bad.

 

[richy3333]

Code 2 and a code 3 for no additional protection with it being T&E - presuming it's in a wall etc?

 

[telectrix]

Code 2 and a code 3 for no additional protection with it being T&E - presuming it's in a wall etc?

never presume. look what happened to the titanic.

 

[SJD]

Thanks for the additional replies.

To sum up, if I’ve understood correctly, for tails over the length permitted by the DNO (typically 3m), suggested EICR code:

	Cable not mechanically protected, e.g. T&E in walls	Cable is mechanically protected, e.g. SWA
Conductor size too small for DNO fuse rating, taking account of installation method(s)	C2 – needs fuse/MCB C3 – recommend RCD	C2 – needs fuse/MCB
Conductor size OK for DNO fuse rating, taking account of installation method(s)	C3 – recommend RCD	No code – though does not meet ESQCR

This always assumes you know the actual DNO fuse size, e.g. a 100A carrier will often have a lower rated fuse fitted, which might not be easily checked.

 

[Guest55]

i'd go along with that ^^^

 

[telectrix]

not 100% happy with the C2's. if the cable is, say, 16mm on a 100A DNO fuse, and has been in situ for years without any signs of damage, i'd lean more towards a C3.

 

[SJD]

I'm inclined to agree, if 16mm2 cable CCC can be as high as 94A for reference method E, it is not that far short of the 100A. The trouble with having just three codes to choose from, with something marginal, I find it can be difficult to decide which code.

A different example I’ve come across a few times recently is small amounts of visible (exposed) live cable or terminals on the suppliers equipment, e.g. on the fuse carrier or meter tails, trying to decide if it should be a C1 rather than C2.