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why can't you get a 3core and earth
Because that would make it a 4 core.
And using the third GY core as a phase conductor was my point. You cannot get a suitable 3 core SY for VSD applications for that reason.
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why can't you get a 3core and earth
it's an exposed conductive part, therefore it must be earthed.
I am not saying yes or no to earthing it, merely where is the guidance. How are you judging its fault current carrying capabilities.This.
And I think it's nuts saying it does not require it. And I just don't care if it's written in a book or not.
If that cable gets damaged that braid is likely to become live.
I am not saying yes or no to earthing it, merely where is the guidance. How are you judging its fault current carrying capabilities.
I never suggested this, my point being if it is required to carry fault current due to cable damage where is the maths to assess its fault current carrying capabilities.I don't think anyone is using the braided screen as an earth cpc. They are just earthing the screen as its a sensible thing to do.
I never suggested this, my point being if it is required to carry fault current due to cable damage where is the maths to assess its fault current carrying capabilities.
I never suggested this, my point being if it is required to carry fault current due to cable damage where is the maths to assess its fault current carrying capabilities.
Their last para is stark : "We therefore urge extreme caution in accepting the use of YY and SY cable types for UK fixed installations, and to contact the BCA on 0208 946 6978 ..."
I never suggested this, my point being if it is required to carry fault current due to cable damage where is the maths to assess its fault current carrying capabilities.
People are quoting it should be earthed in case the cable gets damaged, say by a nail. What happens when the nail causes a short between a line conductor and the braid, fault current flows. So my point is can the braid carry the fault current and sufficient current without any deterioration of the braid to cause disconnection of the circuit. I am not suggesting its use as a cpc, but if it is earthed there is a possibility it may carry current under fault conditions.It would only need to be assessed for fault current carrying capability if used as a cpc surely ?
When earthed it is connected to cpcs whose capability for fault conditions has already been assessed and verified.
That doesn't even warrant a reply.Do you asses this when earthing cable basket?
No, so I don't see the relevance of its ccc especially as it's not a cpc.
Yeah I know you get the drift, interesting you find it acceptable the braid may suffer damage under fault conditions, this is not acceptable and is the point I am trying to make.I understand what you are saying @westward, and this is the very point I have been trying to make, if you wish to use SY then because it falls outside the BS7671 then its down to the installer to confirm if the braiding will be adequate to carry a fault current, the stuff I have used in the past has met this criteria as I have sourced the manufacturing info myself but I cannot say this is the same for every piece of SY out there, but I would say its best to earth than not to, given that even if it does take damage under a L/E fault then it should still trip the OCPD and investigation to why the circuit tripped should see it taken out of service anyway.
It's not really the point whether the braid will suffer damage, but that without earthing it a fault such as a nail penetrating the braid and live conductor will be live.Yeah I know you get the drift, interesting you find it acceptable the braid may suffer damage under fault conditions, this is not acceptable and is the point I am trying to make.
Isn't it, the braid should maintain it's integrity under fault conditions so the circuit disconnects whether the cable is no longer serviceable or not. It seems to be the case for all other circuit configuration unless SY is involved, just earth it job done no thought required.It's not really the point whether the braid will suffer damage, but that without earthing it a fault such as a nail penetrating the braid and live conductor will be live.
Not only that but the braid will be live along the whole length of the installation.
Isn't it, the braid should maintain it's integrity under fault conditions so the circuit disconnects whether the cable is no longer serviceable or not. It seems to be the case for all other circuit configuration unless SY is involved, just earth it job done no thought required.
Whether it is an exposed conductive part is debatable. As a matter of interest how are you assessing the braids ability to carry fault current whilst suffering no thermal stress.Defiantly not. If the braid is an exposed conductive part then it will need to satisfy the regs regarding disconnection time if a fault occurs. This may be earthing it, it may require an rcd. If you can't guarantee the disconnection time then it should not be used.
So you see, lots of thought.
Just ignoring it because you're not sure that it can maintain it's integrity under fault condition would come under the heading 'no thought required'
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