D.I. tails entry to c/u.

[Soulsurfer]

Hey all, regarding the entry of d.i. meter tails into a consumer unit I was called to a recent job to quote for a few alterations and people have just moved in, informed me just before they bought that new consumer unit had been fitted etc.. all looks o.k. but meter tails and main earth have been brought in through a 32mm compression gland / rubber packed, and all t & e's through opened knockout and just grommet strip on top of casing. I am doing a new unit on another job soon and local dno are saying just a standard plastic gland is fine ! I'm thinking what's the point of say Wiska sprint metal glands made for Amendment 3 or intumescent sealants if the dno is saying don't need to ? Those glands aren't cheap and customers want cheap as possible of late !

Rather not leave my work open to problems if not maintaining non-combustible ratings, any opinions ?

 

[Simonslimline]

The OP obviously means insulated and sheathed.....

Too fast as usual.

 

[netblindpaul]

The OP obviously means insulated and sheathed.....

Insulated and sheathed on the other hand!

So why STATE double insulated then?

Sheathing is not classed as insulation in the cable standard.

Get the terms right, get the Engineering right, then it all works.

 

[Leesparkykent]

So why STATE double insulated then?

Sheathing is not classed as insulation in the cable standard.

Get the terms right, get the Engineering right, then it all works.

Its a common mistake made by a few sparks but im sure most knew what the op meant.

 

[Soulsurfer]

Locally & throughout apprenticeship 25 years ago always been referred to as DI tails as in insulated brown / blue eg. 16mm copper then grey sleeve sheath over top, didn't mean double insulated eg class 2 like a DVD player flex ! All wholesalers refer as DI tails even the DNO. obviously someone's a bit pedantic !

 

[netblindpaul]

Its a common mistake made by a few sparks but im sure most knew what the op meant.

Why make assumptions, get facts right and all goes well, make assumptions and things go wrong.
This is one of the major issues with communications these days, people are too lax with FACTS.
Get facts right and the rest falls into place, things are not ambiguous any more.
Ask NASA about Mars Landers, and you'll see what I mean.

It is this exact lackadaisical attitude that is the reason for Amd3 metal CU's and the proliferation of Electrical Trainee, and the general de-skilling of industry, trades and other previously skilled positions.

I HATE it, I HATE the lax attitude, the pathetic grammar, and incompetent descriptions of "stuff" that leads to confusion and ultimately enhances the downward spiral of Engineering.

 

[Darkwood]

The problem is the correct terms and those used out in the real world are 2 different things, most wholesalers will know exactly what you mean by asking for double insulated but say "can I have an insulated and sheathed cable" and you have added 10mins to your visit in trying to explain it.

We all know what the OP meant .. Potato Potarto

Just to add the sheath usually gives the exact same insulating properties with added environmental protection, when manufacturing cables insulation isn't usually sacrificed when giving added properties within the standard cables so using the term Double Insulated isn't wrong.

 

[netblindpaul]

The problem is the correct terms and those used out in the real world are 2 different things, most wholesalers will know exactly what you mean by asking for double insulated but say "can I have an insulated and sheathed cable" and you have added 10mins to your visit in trying to explain it.

We all know what the OP meant .. Potato Potarto

Just to add the sheath usually gives the exact same insulating properties with added environmental protection, when manufacturing cables insulation isn't usually sacrificed when giving added properties within the standard cables so using the term Double Insulated isn't wrong.

I will have to disagree with you DW.
The sheathing does not offer any insulating properties as defined in the British Standard for the wire, thus it is totally wrong to describe it as double insulated, it is insulated and sheathed.
The sheathing ONLY provides mechanical protection according to the cable/wire standard, thus it is simply wrong to describe it as double insulated, like it or not.

 

[Leesparkykent]

Why make assumptions, get facts right and all goes well, make assumptions and things go wrong.
This is one of the major issues with communications these days, people are too lax with FACTS.
Get facts right and the rest falls into place, things are not ambiguous any more.
Ask NASA about Mars Landers, and you'll see what I mean.

It is this exact lackadaisical attitude that is the reason for Amd3 metal CU's and the proliferation of Electrical Trainee, and the general de-skilling of industry, trades and other previously skilled positions.

I HATE it, I HATE the lax attitude, the pathetic grammar, and incompetent descriptions of "stuff" that leads to confusion and ultimately enhances the downward spiral of Engineering.

Cool....

 

[Darkwood]

I will have to disagree with you DW.
The sheathing does not offer any insulating properties as defined in the British Standard for the wire, thus it is totally wrong to describe it as double insulated, it is insulated and sheathed.
The sheathing ONLY provides mechanical protection according to the cable/wire standard, thus it is simply wrong to describe it as double insulated, like it or not.

Sheathing provides environmental protection of which mechanical is one of them, as is insulation, UV tolerance, chemical resistance etc etc and like I said 'insulation' or the 'technical term' - dielectric strength of most common cable sheaths is normally equal or better than the actual insulation, the reason it isn't called an isulation is based on the fact it carries other designed properties for its intended use, I commonly use Lapp, Igus and other specialist cabling in my control/power systems where environmental influences and/or constant flexing is crucial to selecting the correct cable.

Within the BS7671, I agree with you as it treats the outer layer as a sheath for environmental protection but if it offers the same level of insulation then it cannot be defined as incorrect to say double insulation if that is all you require as a quality of the sheath. As long as you know Insulation of the sheath is one of several traits and not its sole purpose then it isn't incorrect to say it, if the wiring standards say it only provides mechanical protection then I would be interested in a link as I deem this as misleading and incorrect.

If however the OP or any member claimed the outer sheath was specifically there 'only!' for one particular trait of a sheath designed for environmental protection with disregard to its full purpose then yes, agree, it would be time to correct them.

 

[stevethesparks]

In my 44 years in the game I have only ever heard them described as d/ins tails, I have never heard them referred to as insulated and sheathed tails. Right or wrong, maybe its a locality thing? Not bothered anyway.

 

[davesparks]

If you look in the section of bs7671 which covers double insulation as a protective mature it says that an insulated and sheathed cable may be considered to provide equivalent protection to double or reinforced insulation if certain conditions are met. So the regulations are clearly making the distinction that insulated and sheathed is not the same as double insulated.

 

[netblindpaul]

OK, first we need to realise that cable standards are in a state of flux at the moment, due to the Construction Products Directive, there is further cable harmonisation across the EEA.

The "cable" we are discussing here is 6181Y to BS6004.

A typical reliable quality suppliers link here:
Draka 6181Y PVC Insulated and Sheathed Wiring Cable
Now if you look at this page, it confirms the cable complies with BS6004, & that there is another kind of “similar” sheathed cable.
6242Y, commonly known as “twin & earth”.

Now there is a clue to the lack of “double insulation” in the wire code.
e.g. 6181Y, NOT, 6181YY.
The single Y denoting a single layer of PVC insulation.

Now if you look here, the cable is described in the British Standard as “PVC Insulated & PVC sheathed”.
BS 6004:2012 - Electric cables. PVC insulated and PVC sheathed cables for voltages up to and including 300/500 V, for electric power and lighting

As has already been suggested BS7671 does draw a distinction between double insulation & insulation & sheathing.

Whilst the sheathing is PVC, and may well be made of the same material as the insulation, and it may offer insulating properties, as far as BS6004 which is the product standard remember, does not call for the sheathing to have any dielectric properties what so ever.

The sheath does not have to undergo any, electrical testing for the cable to meet the requirements of the standard, ergo, it cannot be relied upon as insulation.

The next thing is, looking at the flat twin pvc insulated & sheathed cable with bare cpc.
Now if we stick this in trunking then we can use the bare cpc as a current carrying conductor, because it is insulated by the pvc outer sheathing, as that is the same standard of material ised to sheath the 6181Y.
No we can’t because it is not insulated.

If you look at the description on the Draka site for the twin & cpc, it even states that the cpc is uninsulated, if the sheath was insulation then it would not state that.

I obviously can’t publish the whole of BS6004 as its copyright, and, it also refers to dozens of other standards for testing and material properties.

However, just a quick couple of crops from BS6004 for you:
>>>
1 Scope
This British Standard specifies requirements and test methods for the construction and performance of cables that:
a) have a polyvinyl chloride (PVC) insulation of rated voltage 300/500 V;
b) are intended for electric power and lighting.
The types of cable included in this British Standard are:
• PVC insulated, PVC sheathed cable 300/500 V, single-core 6181Y, flat-twin 6192Y and 3-core 6193Y (see Table 3);
• PVC insulated, PVC sheathed cable with circuit protective conductor, 300/500 V, single-core 6241Y, flat-twin 6242Y and 3-core 6243Y (see Table 4);
• PVC insulated, PVC sheathed cable with or without circuit protective conductor, 300/500 V, single-core 6192Y, 6241Y and flat-twin 6242Y (alternative conductor versions) (see Table 5);
• ordinary duty low temperature PVC insulated, PVC sheathed flexible cable, 300/500 V, flat-twin 3192A, circular-twin 3182A, 3-core 3183A, 4-core 3184A and 5-core 3185A (see Table 6).
<<<

>>>
7 Insulation
7.1 Type of insulation
The insulation shall be one of the following types, in accordance with Table 3 to Table 6:
• TI 1 as specified in BS EN 50363-3;
• TI 4 as specified in BS EN 50363-3.
7.2 Application
The insulation shall be applied by an extrusion process to form a compact and homogeneous layer.
NOTE 1 The insulation can be applied in a single layer, or in a number of cohesive layers.
Where more than one layer is used, all testing specified in this British Standard shall be carried out on the complete insulation as though it were a single layer of the declared insulation type (see 7.1).
NOTE 2 Insulation applied in more than one layer does not conform to the
definition of ‘‘double insulation’’ given, for instance, in BS 7671.
When the application is tested by removing the insulation from the conductor, there shall be no damage to the insulation itself or the conductor.
<<<

>>>
10 Sheath
10.1 Type of sheath
The sheath shall be an extruded layer of PVC of one of the following types, in accordance with Table 3 to Table 6:
• Type 6 as specified in BS 7655-4.2.
• Type 10 as specified in BS 7655-4.2.
10.2 Application
The sheath shall be applied by an extrusion process.
NOTE The sheath can be applied in a single layer or in a number of cohesive layers.
Where more than one layer is used, all testing specified in this British Standard shall be carried out on the complete sheath as though it were a single layer of the declared sheath type (see 10.1).
When the sheath is removed, there shall be no damage to the core insulation when visually checked.
<<<

The title of BS 7655-4.2 is:
BS 7655-4.2:2000 Specification for insulating and sheathing materials for cables. PVC sheathing compounds. General application. General application

So you can see again that the product standard for the sheathing makes a distinction, specifically that it is sheathing compound, not insulation.

 

[jimmy mustard]

 

[Darkwood]

@Netblindpaul

I think you're not seeing what I was saying, yes I know the various standards albeit vaguely governing the cable construction and the fact that the insulation and the sheath are 2 different components of the cable and technically it is incorrect to call tails double insulated.

What I did correct you on was the highlighted points that you said 'The sheath doesn't offer any insulation properties' - regarding the cable under discussion this was an incorrect statement to make as it does, had we been discussing unsheathed MICC then you may have been correct but your statement was a sweeping one thus not true.
I also highlighted the fact that you said 'the sheath ONLY provides mechanical protection', where it can be agreed all sheaths do give some degree of mechanical protection whether that is low or high is another issue but again you statement is incorrect as mechanical properties of a sheath is one of many recognised attributes/properties the sheath may possess and it should be refered to as environmental protection as oppose to singling out one of its properties.

You pulled someone on a technicality of which 'YES' you are correct, but at ground level my argument was the cable under discussion and what the guy/girl behind the counter of the wholesalers understands is the same if its asked for as double insulated and I pointed out that it does give an equal degree of insulation properties so technically it cannot be incorrect to refer to it as having 2 layers insulation although like you did yourself they would be pulling out a single attribute and using as a sweeping statement.

I was just amused you pulled someone for been technically incorrect than did the same yourself twice in a reply to me as I pointed out

I am not generally disagreeing with you but was just expressing the BS7671 treats the sheath as Environmental protection and to say its is only for mechanical protection is like the point you were trying to bring across, technically incorrect.

 

[SP4RKI]

So what does OP mean??