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

 

[chopper]

the braidings on this SY does it have to be terminated at both end as i was doing a job in a factory and the maintainace men were putting this SY for a temp supply to some porter cabins, but they said u only terminate the braiding inn the mains as if u terminate at both side it causes some kind of voltage, they also didnt use the correct type of glands they just used ct adapters that were water proof, what is the negatives about that ( they cable used was 3 core with earth as a core and the braiding as eath aswell )

 

[Darkwood]

Not all SY is control cable - regularly used on 230v.:wink5:

S/Y by its nature and original purpose is a control cable, the braiding is designed for screening but over the years it has been utilised more so as a power cable with protective braiding.... heres the problem... alot of ppl started using the cable for LV power but didn't earth the braiding and i dont mean DIY guys, mechanics etc but so called electricians; this led to many shocks, injuries and some deaths from live braiding because of cable damage and unearthed braiding.... the manufacturers had to cover their backs against the changing use of their cable hence the 'for control use only' or similar words to that effect only because it wasn't been earthed when necessary.
Ive come across several live braiding on damaged cables laid across factory floors over the last decade so cant imagine how many are out there?
From experience i would say 85% of sparkies parrot fashion there job without thinking and because S/Y isn't mentioned in the OSG it dosn't need tinking about...Wrong!!!!... first time i used it i rang the manufacturers for advice on their control use only and was told ^^^above... ive used it for power supplies since while correctly earthing the braiding. But Note! if supplied from different manufacturer than i get it from now i would again ring them and confirm its use as manufacturing techniques and characteristics of cable differ.

 

[chopper]

can this be burried

 

[Darkwood]

the braidings on this SY does it have to be terminated at both end as i was doing a job in a factory and the maintainace men were putting this SY for a temp supply to some porter cabins, but they said u only terminate the braiding inn the mains as if u terminate at both side it causes some kind of voltage, they also didnt use the correct type of glands they just used ct adapters that were water proof, what is the negatives about that ( they cable used was 3 core with earth as a core and the braiding as eath aswell )

It could be treated like an armoured with earth core but because the braiding is doing a mechanical protection it would require earthing at a minimum from the supply end, there reasoning about earthing one end only would depend on it use, earthing one end only is more akin to control situations in machinery where circulating currents may be creating and cause issues but as just a power supply cable its not a issue, to note on this subject though the braiding requires earthing but must not be used as the earthing for the cable 'a seperate earth core must be used!'.

 

[Darkwood]

can this be burried

I wouldn't have thought so without a protective conduit or ducting, but again consult manufacturer if this is an intention, again ive seen it done and all that ive found is depleted/damaged outer sheath and brown corroded braid to boot, underground conduits and ducts can be prone to water ingress, i wouldn't directly bury any cable unprotected with exception of SWA.

 

[One_of_them]

hmm good stuff this.

so would you run another earth to make it high integrity?

 

[Darkwood]

Ive already high-lighted the section and even the regulation regarding the options you have with High integrity earthing, all the info is in there - we are guiding you here so expect you to do some of the research when given direction, we cant say anymore than we already have without knowing earth current etc and whether the unit can be expanded in future thus needing allowances... other than doing the job for you i think its time to read your regs now where we have directed you, we are happy to help but have to draw a line or you'll never learn your job.
Hint the reg# i gave earlier explain in point no (iii) about using cables with earth core and armour or braid, i really cant do much more for you.

 

[One_of_them]

thanks very much all for your help. Found your assistance excellent and checked the reg you quoted and I'm happy that using 10mm SY utilising the braid as high integrity will suffice.
But with this comes the next problem with high integrity earthing been required, I have never seen a 5 pin commando with dual earth terminals......

These units come with a 5 pin commando fitted so looking at reg 543.7.1.102(ii) would suggest high integrity is not required?

 

[Darkwood]

thanks very much all for your help. Found your assistance excellent and checked the reg you quoted and I'm happy that using 10mm SY utilising the braid as high integrity will suffice.
But with this comes the next problem with high integrity earthing been required, I have never seen a 5 pin commando with dual earth terminals......

These units come with a 5 pin commando fitted so looking at reg 543.7.1.102(ii) would suggest high integrity is not required?

You need to use a seperate earth core for the high integrity earthing and also earth the braiding if cable has one, unless you have access to the csa and electrical characteristics of the braiding which is doubtful you shouldn't use it as the high integrity earth for the load.

 

[Guitarist]

can this be burried

I certainly wouldn't bury it.

 

[One_of_them]

guys,

sorry to bring this back up. Has anybody ever seen a commando with 2 earth terminals? Searched the net but nothing has appeared. Or as I have said above would the fact it will be connected by a commando negate the requirement for high integrity? I feel that the circuit should but the equipment does not need.

 

[Darkwood]

here lies the problem with using S/Y for purposes out of its original design.... if you use a 10mm 4core and earth Y/Y flex then the braiding isnt gonna be an issue anymore.. why are you requiring the power cable to be screened?, the high integrity earth is required which ever method you adopt but not sure why you need a screened cable?

 

[One_of_them]

this was just a request from the client. They wanted the new circuit to match the others already in.
I will happily explain that we can use an alternative cable although this will highlight the fact their current, recent installed circuits do not comply.
Still going to need a 5 pin commando with dual earth though???

Darkwood you have been a legend with this so thank you

 

[Darkwood]

You only need a duel earth if you have braiding to earth too and yes ive had this predicament myself so now i never fit commando style gear, the SY is usually chosen due to its harder wearing but unless you in an area that requires a more abrasive resistant cable then you dont require one, ask the customer his reasoning for SY then point out the issues in its use in said situe, it could always be run in a nylon flexi conduit if its in a area where it may get damaged as a stand alone Y/Y flex.
As mentioned before lack of mA leakage info would lead to air on caution and fit a 4core and earth 10mm YY, this will require ferrules fitted when making of been a fine wire cable, but only 1 earth terminal needed then.
Its nice to try let the customer get exactly what they want but be cautious that the cart dosn't start leading the horse.... if you get my drift

 

[One_of_them]

surely if I am to install high integrity then with or without the braid I would need dual earth terminals in the commando anyway to get the earth core of cable plus the 2nd 10mm to achieve high integrity
The braiding I was planning on terminating in the board using the correct gland.
the area is not hazardous etc so tbh the extra protection aint really required. I think the reasoning was just so it looked the same.
No info on the unit but I now know it is a PDU but dont know what type etc. These come pre-fitted with a commando so I'm less inclined to chop this off LOL