SY flex

[One_of_them]

Guys,

I'll be honest ive never had much chance to work with this stuff.

Been asked to run a 32A 3-phase supply for some IT equipment. Looking around it appears somebody has been in previously and ran a similar setup in SY flex 10mm I think. They have used normal glands into the board but I aint opened it up to see if the braid has been terminated. Last time I saw this stuff used was on a production line and the braid was just trimmed off and tapped over.
I know about the correct glands to use but other than this is there anything that I may need to be aware of. Its only a short run to so would have thought 6mm would suffice?

cheers

 

[Darkwood]

I think your misunderstanding the reg's here, if you have a 10mm earth then you comply so having this within your supply cable will suffice but doing so your live conductor will have to match its size (10mm) no need for extra earth... duel earth terminals are normally associated when you loop earth in and out to next point like a ring main, its a mechanical connection in that if an earth terminal is loose on one point it has an alternative connection, the regs you are interested in are for a radial hence the size of cable.
I think your confusion here is that you need a second earth for high integrity earthing but if your cable is big enough hence 10mm 4core and earth it complies, but if you had a smaller cable you may have to run a seperate earth to meet regs so as suggested running a 10mm 4core+E will be adequate.... all on the assumption that earth leakage may exceed 10mA

 

[jonah84]

Hi guys just come across this thread and thought i would share my experience with sy flex with regards to whether the braiding should be earthed or not. Imho i agree it should be earthed but not used as an earth as has been said already. This was the practice we used to adopt when using this type of cable until our local NIC inspector called my boss up on it and asked us why we were earthing the braiding his view was that the braiding would not be able to withstand the fault current so was pointless i still dont agree with this but my boss says he must have a valid point he is an NIC inspector after all
Just thought i would throw another spanner in the works lol its stuff like this that really annoys me i have just come out of my time and it seems there is far to much confusion and conflicting advice out there! Its no wonder you see so many mistakes on site from supposedly qualified electricians!

 

[Rauer]

I would never use the braid of an sy for the earth, however I would always connect it to earth to provent any induced currents

 

[Darkwood]

Hi guys just come across this thread and thought i would share my experience with sy flex with regards to whether the braiding should be earthed or not. Imho i agree it should be earthed but not used as an earth as has been said already. This was the practice we used to adopt when using this type of cable until our local NIC inspector called my boss up on it and asked us why we were earthing the braiding his view was that the braiding would not be able to withstand the fault current so was pointless i still dont agree with this but my boss says he must have a valid point he is an NIC inspector after all
Just thought i would throw another spanner in the works lol its stuff like this that really annoys me i have just come out of my time and it seems there is far to much confusion and conflicting advice out there! Its no wonder you see so many mistakes on site from supposedly qualified electricians!

I can only assume the NIC inspector was under was under the impression the braiding was been used as the earth with respect to been earthed for safety as it is exposed at its termination, also from experience ive have found live braiding on a few occasion when a cable has suffered damage and had this been earth the fuse would have operated but instead posed a high safety issue.

Dont be clouded by the title NIC inspector, ive corrected both Clark of Electrical works and NIC inspectors myself on varying issues over the years, if you see a valid reason for your argument then explain it and see what reasoning they offer, i could agree that the braiding is not designed as the earthing fault path but with all due respect when using it as a tough wear power flex then the braiding should be earthed due to the safety issues that it could present if it wasnt.
On a side note, some SY suppliers do state within ttheir cable bumf' that it should not be used as a power supply cable, its original design was as a screened control cable so caution as to manufactures guidelines before changing its use, i made a call regarding this issue and they specified it can be used as a power flex if correctly glanded and braiding is earthed but not used as the earth (seperate earth core needed).

It would be nice if we could get a representative from one of the major bodies to argue their corner as you say it is down to interpretation and even those at the top get it wrong sometimes as they often are interpreting from an office environment where as on site application of the regs can sometime show flaws and issues not thought of, hence the massive changes in regulations since the 15th and between the 16th and 17th. Just browse any ammendment to any addition and you'll realise how fallable the current reg's are