Meter tails

[ianphilip007]

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

 

[IQ Electrical]

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.

 

[ianphilip007]

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.

 

[IQ Electrical]

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.

 

[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?

 

[Swicade]

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

 

[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?

 

[ianphilip007]

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.

 

[ianphilip007]

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.

 

[Plonker 3]

A main switch in a DB?

 

[IQ Electrical]

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.

Check post #4

 

[Jimmy Boy]

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]

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.

 

[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

 

[ianphilip007]

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.