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.
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?
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
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.
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.
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.
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
The reason for using the SY is that the part derelict building has SWA's, Conduits, T&E running everywhere. so SY stood out like a sore thumb in contrast to all the dead circuits that were still in. and yes i used the correct glands.
The reason for using the SY is that the part derelict building has SWA's, Conduits, T&E running everywhere. so SY stood out like a sore thumb in contrast to all the dead circuits that were still in. and yes i used the correct glands.
On a job recently the aircon guys used SY everywhere, at every accessory they had just used stuffing glands. They were not happy bunnies when it come to snagging and I made them change all the stuffing glands for XT/CXT glands with banjos and fly leads where necessary:hurray:
On a job recently the aircon guys used SY everywhere, at every accessory they had just used stuffing glands. They were not happy bunnies when it come to snagging and I made them change all the stuffing glands for XT/CXT glands with banjos and fly leads where necessary:hurray:
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