Use of sy cable

[davesparks]

But on the other hand, not earthing it could cause it to become live if damaged?

And if its not up to carrying the fault current then it will melt at some point leaving the remaining parts of the braid live.

 

[westward10]

I really dislike sy cable for anything other than maybe industrial machine wiring, I come across it as a maintenance spark all the time and see mechanically biased engineers installing final circuits using it because "it's easier" but when you correctly earth the braiding it is not easier to install it's as easy to install armoured cable and you cut your fingers on the braiding and does not comply with the regs to boot. The braiding must be earthed or could potentially become live if the cable got bumped or damaged in some way. I would record as c3 if this is not the case, just a very odd cable for domestic use!

Where is it cited SY cable braid must be earthed and how do you confirm it can carry fault current without suffering undue thermal stress.

 

[HappyHippyDad]

Where is it cited SY cable braid must be earthed and how do you confirm it can carry fault current without suffering undue thermal stress.

Well you have to tell us now Westward because we all want to know?

 

[Zdb]

The manufacturer's instructions state that it must be earthed.

Also SY glands are designed so that the braid is earthed.

 

[Bobster]

Simple answer is that it's not recognized by BS7671, I would have thought a C3 would be appropriate.

Dependent on the condition of the SY etc..

 

[cliffed]

Lots of agree & disagreement on this,not the best cable to be used,on whatever.
The braid needs to be earthed,similar to the sheath of a Swa cable.
Doubt very much if the braid will carry the earth fault current,may do over a short time until the mcb,Rcd operates.
This I assume is why it’s not recommended nobody bothers to connect the braid,which really is a no no.

 

[westward10]

Lots of agree & disagreement on this,not the best cable to be used,on whatever.
The braid needs to be earthed,similar to the sheath of a Swa cable.
Doubt very much if the braid will carry the earth fault current,may do over a short time until the mcb,Rcd operates.
This I assume is why it’s not recommended nobody bothers to connect the braid,which really is a no no.

If a circuit is correctly designed fault current should only be for a brief duration nevertheless the braid must be able to withstand this. How are you deciding upon this when you connect it to earth.

 

[Bobster]

Lots of agree & disagreement on this,not the best cable to be used,on whatever.
The braid needs to be earthed,similar to the sheath of a Swa cable.
Doubt very much if the braid will carry the earth fault current,may do over a short time until the mcb,Rcd operates.
This I assume is why it’s not recommended nobody bothers to connect the braid,which really is a no no.

It is designed as a machine control cable. Not for fixed wiring. I belive the confusion arose once manufacturers started producing it with Brown, Blue and GY core colours.

It also, only complies with the German VDE standards, hence not accepted by BS7671.

It's not UV or water resistant. The braiding is a screen, not designed to take fault current.

 

[Ian1981]

The braid is sometimes earthed for screening purposes only, so it doesn’t necessarily need earthing for the reason of fault protection only.
Perhaps should be installed with additional mechanical protection to reduce faults to a minimum.
Irrelevant in this scenario I know.

Only good for control wiring as stated by the manufacturers and should be installed as per manufacturers instructions.

 

[cliffed]

If a circuit is correctly designed fault current should only be for a brief duration nevertheless the braid must be able to withstand this. How are you deciding upon this when you connect it to earth.

I’m not,it’s recommended the braid is connected to earth be it functional or protection,obviously the manufacturers,have tested this to their standards only.

 

[DT1991]

Is NYY-J accepted by BS7671

 

[Bobster]

Is NYY-J accepted by BS7671

Yes, they comply with the following standards: IEC 60502-1, BS EN/IEC 60332-1-2

There are some caveats for them complying if they are to be buried. Mainly they have to be in ducts rather than direct burial.

 

[polo1]

Ok, thanks for the views ( tho we’ve gone a bit off track re earthing the braid). Any other thoughts on Coding & why?

 

[Zdb]

C3 as long as there's nothing wrong with the cable I.e damaged insulation etc.

 

[Dustydazzler]

Just replace the cable with a bit of heat rubber flex

 

[Zdb]

Ok, thanks for the views ( tho we’ve gone a bit off track re earthing the braid). Any other thoughts on Coding & why?