SY, CY None Compliant????

[HappyHippyDad]

So, I'm out on site the other day and the apprentice is installing some SY cable for a ring final circuit. Anyway, we got chatting and he mentions that this type of cable does not comply with BS7671! I said, "of course it does, it's part of the AM2 and it is one of the 7 cable types of the new 2357 apprenticeship NVQ! So out of curiosity I had a look. To my suprise, it does state in the BS7671, that this type, along with YY, CY are none compliant!! I know that most of this multi-core cable comes with none standard colour cores etc but does any one know an actual reason why it is none compliant? I am genuinely interested.

Cheers

Jay

Could you point me to the page or reg of BS7671 where it says this JS? I'd be interested to read it, thanks.

 

[GEOFF S]

Could you point me to the page or reg of BS7671 where it says this JS? I'd be interested to read it, thanks.

Hi

Im pretty sure its comes down to the braided screen not meeting the relevant requirements for mechanical protection, also probably issues with regard the braid and fault current.

Cheers

 

[shanky887614]

go be honest as long as its used inside and it doesnt require mechanical protection 3c (L,N,E) sy is fine.

to be honest most of it ive used has been in trunking from vsd's to motors with a stuffer out of the trunking then into the motor case

Sent from my SM-G935F using Tapatalk

 

[davesparks]

Could you point me to the page or reg of BS7671 where it says this JS? I'd be interested to read it, thanks.

Somewhere there is a reg which says that heavy duty flex is to be used for installation work, and SY doesn't fall in to that category

 

[Adam W]

.... seen plenty of live un- earthed braid on this stuff over the yrs ...

I've found loads of this at my place, which was installed by the mechanical guys. It gets my goat - why even bother if you're not going to earth the braid? You may as well just use H05.

IMO SY has it's uses, such as where you need something more flexible than SWA but there is a danger of someone going through the cable with anything - if the sheath is earthed contact will be made with that before a live conductor so the protective device should operate.

 

[Flanders]

I thought the brade was for a screen and not designed to carry a fault current thats why is has a seperate cpc within the cable.

 

[Davisonp]

Somewhere there is a reg which says that heavy duty flex is to be used for installation work, and SY doesn't fall in to that category

[h=5]521.9 Use of flexible cables[/h]521.9.1 A flexible cable shall be used for fixed wiring only where the relevant provisions of the Regulations are met. Flexible cables used for fixed wiring shall be of the heavy duty type unless the risk of damage during installation and service, due to impact or other mechanical stresses, is low or has been minimized or protection against mechanical damage is provided.
NOTE : Descriptions of light, normal and heavy duty types are given in BS EN 50565-1.

 

[Adam W]

I thought the brade was for a screen and not designed to carry a fault current thats why is has a seperate cpc within the cable.

You can have a separate CPC within an SWA, but the armour should still be earthed.
Either way the braid of SY flex should be earthed.

 

[davesparks]

I've found loads of this at my place, which was installed by the mechanical guys. It gets my goat - why even bother if you're not going to earth the braid? You may as well just use H05.

IMO SY has it's uses, such as where you need something more flexible than SWA but there is a danger of someone going through the cable with anything - if the sheath is earthed contact will be made with that before a live conductor so the protective device should operate.

But the braid is not rated for the fault current, so it is pretty much the same as installing PVC insulated and sheathed flex as far as any protection goes.

 

[davesparks]

You can have a separate CPC within an SWA, but the armour should still be earthed.
Either way the braid of SY flex should be earthed.

Earthed yes, but it cannot handle fault current so cannot be used to provide any protection such as that provided by SWA, MICC or any bs8436 cable

 

[ruston]

Well , here is an overview from Eland Cables on SY.
It may answer a few of the questions.
SY Cable | Eland Cables

And a manufacturer that says it can be used outdoors if it is protected.
It's all down to researching the product to suit what you need

http://uk.rs-online.com/web/p/sy-cable/0522531/

 

[SheffSimon]

But the braid is not rated for the fault current, so it is pretty much the same as installing PVC insulated and sheathed flex as far as any protection goes.

Thats because its a control cable, not a power cable.

TBH I can't think of a situation where I would spec or accept SY.

 

[Adam W]

Earthed yes, but it cannot handle fault current so cannot be used to provide any protection such as that provided by SWA, MICC or any bs8436 cable

I see. So what would happen if for example you were to go through the earthed braid with a grinder or a chisel or something, and into the live conductor?

 

[davesparks]

I see. So what would happen if for example you were to go through the earthed braid with a grinder or a chisel or something, and into the live conductor?

Subject to a few variables the two likely outcomes are:
1 the braid melts before the ocpd clears the fault
2 the ocpd clears the fault before the braid melts.

Firstly if an rcd is in use then it should clear the fault.
If the fault current is high enough to cause instantaneous operation then scenario 2 is likely.
If the fault current is low enough that the ocpd does not operate instantaneously then situation one could occur.
Both options could easily result in a cloud of vapourised molten metal

 

[LeeH]

Also consider most people just use stuffers and peel back a few strands. So Daves option 1 the most likely.

 

[Midwest]

Used miles of the stuff back in my days in the car factory, for conveyor systems etc. It was specified then, as it provided more of a durable cable than heavy duty flex. Guess approved practises change over time, probably end up with twin & earth being 'discouraged' in due course.

 

[i=p/u]

Seeing quite a bit of everyday and guess what it's never earthed..
most used for em stops and motors.

 

[Spoon]

We sometimes use SY for power between the power dist board and other equipment in the installation. Only when SWA is not needed.
I contacted Eland to see what they thought and below is their response: They responded really quickly which is always great and I have ever had a problem with these people.

Themain issue is that YY and SY cables are being applied incorrectly, for exampleYY cables have been installed as a replacement for Twin & Earth, SY cableshave been used in direct burial applications as a replacement for SWA. Theadvice given is that cables used for compliance with BS 7671 need to complywith a published British Standard, or UK adoption of a CENELEC standard. Thiswill depend on the installation.

With regards not using SY and YY cables in fixedapplications , the reasoning behind this is given within the new onsite wiringguide published by IET is that the SY and YY cables have not been made to aspecific standard.

There have been a number of articles published by BASEC, NICEIC and ACIregarding the use of YY, CY and SY cables, the articles identify that thesecables are not included in BS7671 and are therefore could potentially not be fit for purposeas fixed wiring cables, please find below links:
http://www.basec.org.uk/News/BASEC-News/Be-Cautious-of-Midleading-Claims-Associated-with-YY-and-SY-cables
http://www.aci.org.uk/news/aci-issues-warning-installers-over-cable-claims

 

[westward10]

Just because something is not recognised by BS7671 it does not mean you cannot install with it. The cores of this cable, apart from the cpc may well all have black insulation but they are numbered. For good measure protect it with a type 4 protective device something else which was not recognised but used extensively.

 

[High Tower]

I would always be selective about where i use SY, last time i used it was for temporary lighting within a semi derelict building. all clipped to the ceiling out of harms way.

And when i used to do the very odd few houses i would use YY to connect cookers to the outlet plates. apart from that dont use the stuff.

Tell a lie, used some YY the other day to flex up a couple of UPS's