SY Flex query

[Dean Williams]

Hi Folks
I'm testing a factory where a lot of circuits are wired in SY flex. The metal glands have not been fitted, just normal pvc compression glands and the metal braid on the flex has not been earthed.
The problem is, between the unearthed braid and the earth terminal in the DB, im getting between 24-50v only when the cable is energised.
Is this the copper cores inducing an EMF in the braid? if it is, then i thought that the live and neutral within the flex would cancel out the emf produced.
If its not this, can someone please explain??

Thanks

 

[johnboy6083]

If you carry out an Ir test between the braid, and each core in turn, and ensure that the braid is insulated from any external influences, then that is the conclusion that i can come too.

 

[Dean Williams]

IR was fine. all readings >200 meg ohms.
from what ive read on the net, a current cannot be induced into the armour of a multicore cable, so what are the readings im getting. its not just one one DB, its on them all.

 

[jamie-spark]

Hi Folks
I'm testing a factory where a lot of circuits are wired in SY flex. The metal glands have not been fitted, just normal pvc compression glands and the metal braid on the flex has not been earthed.
The problem is, between the unearthed braid and the earth terminal in the DB, im getting between 24-50v only when the cable is energised.
Is this the copper cores inducing an EMF in the braid? if it is, then i thought that the live and neutral within the flex would cancel out the emf produced.
If its not this, can someone please explain??

Thanks

Dean you are correct there is a emf being picked up. i had the same thing in a section of unearthed steel conduit. Think you will have to code 2 this as its uneathed and the braiding is classed as an exposed condutive part. With ref to GN8

 

[Dean Williams]

Thanks Jamie
i think there will be a lot of code 2s.
if there was a prize for the most SY flex circuits in a single factory...europackaging would win it hands down (and all of them have unearthed braiding!)

 

[mogga]

the use is comoignin more and more specialy for smaller circuits 6mm and less probably down to cost and flexability against SWA its a bum of a stuff to terminate correctly if you dont have the correct glands iv seen the cores brought through split in braiding with the braiding wrapped together then terminated to earth bar wrapped in pvc tape Not ideal but better than situation you have got there
the other thing iv seen with it is cores not coloured just going by the numbers printed on it looks dodgy as hell all black cores

 

[Dean Williams]

thats what theyve got here. all black cores

 

[johnboy6083]

after reading this, i clamped braidingfrom sa pump cable that was fed by a VSD. i got 6-12A fluctuating, This was tied to earth too! i reckon i would get some high voltages if the braiding and the cable armour was isolated from earth.

 

[Dean Williams]

i managed to get 50v

 

[nickblake]

i always keep some cw20s on my van these work well with the braid , but obviousley better with the correct glands when i install the cables with black cores i either sleeve then on the smaller cables or use a cable tie with L and N and coloured coded too found them on ebay

 

[netblindpaul]

Nothing wrong with all black cores, all black cores = a.c. Power, which is what you are looking at.
Please refer to BS EN 60204-1 which is the machinery "equivalent" of BS 7671.
The requirement for colour coding depends on the application.
Under 60204 there is no need to colour code.