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hi all

The regulations re meter tails and double insulation seem very unclear. Now a meter tail is insulated and sheathed to my mind and does not include reinforced insulation, no double square marking. i might be missing something here but why would a small amount of exsposed inner core present any danger. the tails are not double insulated, and fault protection is being provided by the main fuse, and the tails are enclosed in the C.U.enclosure. as i said i might be missing something
 
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hi all

The regulations re meter tails and double insulation seem very unclear. Now a meter tail is insulated and sheathed to my mind and does not include reinforced insulation, no double square marking. i might be missing something here but why would a small amount of exsposed inner core present any danger. the tails are not double insulated, and fault protection is being provided by the main fuse, and the tails are enclosed in the C.U.enclosure. as i said i might be missing something
You're absolutely correct, 'meter tails' are not double insulated but everyone refers to them as that.
'Exposed inner core' is fine in an enclosure etc. but the regulations make no distinction between 'meter tails' and sub-circuit wiring when it comes to insulation requirements.
 
  • Thread Starter Thread Starter
  • #3
yes completely understand the need for the sheath outside the enclosure. just dont understand why 1 or 2mm of exsposed inner core at the main switch which is in an enclosure, is such a big problem. have my elecsa assessment shortly and its one of the things they advise to look out for. I just like to know why rather that just knowing thats what you do.
 
yes completely understand the need for the sheath outside the enclosure. just dont understand why 1 or 2mm of exsposed inner core at the main switch which is in an enclosure, is such a big problem. have my elecsa assessment shortly and its one of the things they advise to look out for. I just like to know why rather that just knowing thats what you do.
Do you mean exposed copper or insulated inner core?

If exposed copper then there really shouldn't be any need for any.
Exposed insulated inner core is just good practice to keep it to a minimum but you'd still be compliant removing the outer sheath completely within the enclosure or containment.
 
P

Plonker 3

hi all

The regulations re meter tails and double insulation seem very unclear. Now a meter tail is insulated and sheathed to my mind and does not include reinforced insulation, no double square marking. i might be missing something here but why would a small amount of exsposed inner core present any danger. the tails are not double insulated, and fault protection is being provided by the main fuse, and the tails are enclosed in the C.U.enclosure. as i said i might be missing something
If we were allowed single sheathed cable outside a enclosure there would be no need for us to wire in twin and earth would there?
 
S

Swicade

I would take the '1-2mm inner core' regulation as meaning the copper core personaly
 
P

Plonker 3

So you mean either copper with a little sticking out of a terminal or a little of the inner sheath sticking outside a enclosure, which is it?
 
  • Thread Starter Thread Starter
  • #8
If we were allowed single sheathed cable outside a enclosure there would be no need for us to wire in twin and earth would there?
i did state that the exsposed inner core, or inner insulation on the tails would be enclosed within the C.U. in both of my previous posts.
 
  • Thread Starter Thread Starter
  • #9
So you mean either copper with a little sticking out of a terminal or a little of the inner sheath sticking outside a enclosure, which is it?
neither, i am taliking about the inner insulation being exsposed at the main switch. no bare copper anywhere and no inner sheath outside any enclosure.
 

Jimmy Boy

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Arms
Seems the same as any PVC/PVC cable to me, inner for insulation, outer for mechanical protection, once in enclosure outer mechanical becomes irrelevant, my pet hate is seeing ANY copper on tails in to a MS or RCD it's bloody dangerous and poor workmanship, the terminals are recessed up to a point to prevent the pinkys getting zapped but leaving copper exposed is unforgivable..Treat it as you would the bus bar...Deadly !
J
 

darkwood

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Most switches, mcb's meters etc are designed to BS standards and are usually what we call finger safe with the clamp recessed a little, the exposed copper should be within the clamp only with the (inner) sheath butting up the the clamp face, where clamps are too large to be finger safe they usually come with a clip or screw on guard, if the termination is within an enclosure then their are no reg's regarding the extent of the outer sheath of a double sheathed cable is stripped but good practice is enough to identify the colour of the inner sheath without the need to remove cable from clamp.
If the double sheath isn't enclosed when terminated (meter) then the outersheath needs to butt up to the clamp or the recess provided in design as the outer sheath provides environmental protection for the inner insulation sleeve from common chemicals and moisture aswell as added mechanical protection. The inner sheath dosn't usually have the same environmental resistance hence in double sheathed cables it common to find the inner sheath softer and more easily damaged. Where cables are single sheathed it tends to provide a both environmental and insulation resistance but without the added mechanical resistance.
Hope this clears it up a bit.
 
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P

Plonker 3

Seems the same as any PVC/PVC cable to me, inner for insulation, outer for mechanical protection, once in enclosure outer mechanical becomes irrelevant, my pet hate is seeing ANY copper on tails in to a MS or RCD it's bloody dangerous and poor workmanship, the terminals are recessed up to a point to prevent the pinkys getting zapped but leaving copper exposed is unforgivable..Treat it as you would the bus bar...Deadly !
J
I don't know still can't beat the old C50 DBs :p
 
  • Thread Starter Thread Starter
  • #15
if the termination is within an enclosure then their are no reg's regarding the extent of the outer sheath of a double sheathed cable is stripped but good practice is enough to identify the colour of the inner sheath without the need to remove cable from clamp.

Read more: http://www.electriciansforums.net/e...al-forum/60831-meter-tails.html#ixzz21AHlDbde

this is my understanding too and makes a whole lot of sense. just baffles me as to why Elecsa deem exsposed inner insulation on main tails at C.U. main switch to be a problem. there is no regulation to back it up.
 

darkwood

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if the termination is within an enclosure then their are no reg's regarding the extent of the outer sheath of a double sheathed cable is stripped but good practice is enough to identify the colour of the inner sheath without the need to remove cable from clamp.

Read more: http://www.electriciansforums.net/e...al-forum/60831-meter-tails.html#ixzz21AHlDbde

this is my understanding too and makes a whole lot of sense. just baffles me as to why Elecsa deem exsposed inner insulation on main tails at C.U. main switch to be a problem. there is no regulation to back it up.
You got their no# so express your understanding of the regs and query their position, after all if your supply to a DB is an swa armoured then its only single insulated at termination... should we be all heat-shrinking a outer sheath on it all.... i doubt it-- the regs are complex and interpretation can be wrong by the very people you expect to understand it so as i said ring them to confirm as either you have misinterpreted what you have been told or the guy who told you this is himself a bit confused.
Are you sure they didnt mean the CU position but the tails entering the Henley block or meter and not within the CU as you suggest now that would make sense. Many a time ive seen a 40plus post thread debate an area then it turns out the OP had made a misinterpretation rather than the story we have been lead to believe.
 
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1

1shortcircuit

if the termination is within an enclosure then their are no reg's regarding the extent of the outer sheath of a double sheathed cable is stripped but good practice is enough to identify the colour of the inner sheath without the need to remove cable from clamp.

Read more: http://www.electriciansforums.net/e...al-forum/60831-meter-tails.html#ixzz21AHlDbde

this is my understanding too and makes a whole lot of sense. just baffles me as to why Elecsa deem exsposed inner insulation on main tails at C.U. main switch to be a problem. there is no regulation to back it up.
Identification of the conductor at point of termination means that there is no need to see the colour of the inner insulation (brown/blue tape or l/N tape). Also, the big L/N on each terminal should be enough of a give away to work out which is which ;)
 

darkwood

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1short.. he was responding to my post and in response to yours, there is no regulation stated that the outer sheath of a 2 sheath cables cannot be stripped back in any way when within an enclosure whether it be a dist board or other enclosure, the OP has been told the exposed inner sheath is an issue and in agreement with the OP we dont believe this to be the case, and when termination into a Dist' board is made - identification is only neccesary when wiring in singles, 2 differing colour codes present and when not doing so may lead to confusion so exposing 20mm of inner sheath negates the need to waste ID tags on the tails as its visually clear that polarity(confirmed with a test) and inner sheath colour coding are correct.
I always have and will continue to reveal a section of inner sheathing to present the sheath colour code when terminated within an enclosure, this thread is looking for a regulation against doing it not for a solution to identifying the cable if outer sheath is left fully on.
 

JD6400

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I am with you Darkwood , and personally would go as far as saying that it is bad practise not to leave 10 - 20mm of inner sheath exposed when terminating inside a enclosure if not identifying the cable with L/N or coloured tape .
 

darkwood

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It beggars the question on how we are allowed single sheathed cables if what the OP was told was the case.
 

Jimmy Boy

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I've just ordered some double Blu/Blu Brn/Brn tails so no mistaking them lol.
J
 
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