Use of sy cable

[polo1]

Peeps,
Your thoughts please on the use of sy cable in a domestic setting.
Came across an installation today where the supply to an immersion element had been run in sy cable. Overcurrent protection correct and circuit is covered by a 30mA rcd.

I think we are going to be doing an EICR in the property in the next few weeks and couldn’t decide how this might be coded.

What do you think?
TIA

 

[DT1991]

No code if installed correctly. IMO

 

[Zdb]

It does not comply with BS7671

 

[Zdb]

Has the braiding been correctly earthed on the SY cable in question?

 

[Dustydazzler]

SY for an immersion heater is a very odd choice of cable

 

[Strima]

C3 for me as not a suitable cable as this is not its intended use. Also as this is near s heat source the plastic coating will become brittle and crack over time.

 

[westward10]

Has the braiding been correctly earthed on the SY cable in question?

If you are going to earth it how can you be sure it is capable of carrying fault current if required.

 

[Zdb]

If you are going to earth it how can you be sure it is capable of carrying fault current if required.

IMO the braiding must be earthed but not used as an earth! I don't know its capability of carrying the fault current as not enough information has been provided.

 

[westward10]

IMO the braiding must be earthed but not used as an earth! I don't know its capability of carrying the fault current as not enough information has been provided.

Why are you earthing it. No it can't be used as a cpc but connecting it to earth leaves the possibility it could be subjected to fault current and if this is the case you must be satisfied it can carry the fault current.

 

[SparkySy]

I went to a farm with all the out buildings wired in SY not so long ago. Apparently done by a full NIC contractor. I didn't bother to argue with the farmer but it was rubbish none of the screens were earthed just cut off and taped up through stuffing glands.
What a waste of time and money when there are much better spec cables that can be used!

 

[StephenRowley]

Posted in error

 

[Dustydazzler]

I went to a farm with all the out buildings wired in SY not so long ago. Apparently done by a full NIC contractor. I didn't bother to argue with the farmer but it was rubbish none of the screens were earthed just cut off and taped up through stuffing glands.
What a waste of time and money when there are much better spec cables that can be used!

You would be amazed by the amount of ‘electricians’ who just cut off the braiding

 

[Zdb]

Why are you earthing it. No it can't be used as a cpc but connecting it to earth leaves the possibility it could be subjected to fault current and if this is the case you must be satisfied it can carry the fault current.

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

 

[davesparks]

Why are you earthing it. No it can't be used as a cpc but connecting it to earth leaves the possibility it could be subjected to fault current and if this is the case you must be satisfied it can carry the fault current.

Not connecting it to earth will lead to capcitively coupled voltages appearing on the braid.

 

[westward10]

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

In which case it would have to carry fault current.

 

[SparkySy]

Which takes you back to proving it can take fault current!

 

[Robson689]

You would be amazed by the amount of ‘electricians’ who just cut off the braiding

When we were taught terminating SY in college we were also always told the braid must be earthed but you must also have a dedicated CPC. The SY glands earth it anyway so don't see how it can be avoided unless plastic CU?

 

[SparkySy]

I've seen it used wrongly with plastic stuffing glands many times before just taped up! That would stop any continuity to earth.

 

[Tim Watkiss]

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!

 

[Tim Watkiss]

When we were taught terminating SY in college we were also always told the braid must be earthed but you must also have a dedicated CPC. The SY glands earth it anyway so don't see how it can be avoided unless plastic CU?

People always just use a 20mm plastic gland to enter the db and don't earth the braiding I installed a circuit in a factory and there were 4 sy circuits all like this on that db and probably hundreds across the factory

 

[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?