Steel Wire Braided cable

[GMjohn]

The situation - Cables were laid in a customers garden ready for lighting and power installation a few years ago by some other electrician but never finished. We've been called in to finish the job. As a trainee, I've been told by my boss to try and figure it out before work commences, but I have some confusion.

Looking at the lighting cable that's been installed, it looks like sy cable - transparent flexible cable with steel wire braiding. It wasn't connected into the ip junction boxes correctly as they all had water in them. All the cables have water damage to an extent - mould getting inside the ends to various degrees under the sheath and some discolouration/rust on the braiding in places. The cable still tests ok.

Looking at the way the cable was terminated at various boxes, an internal conductor was used for the cpc, and the steel braiding was not earthed. The braiding just had tape around it where the sheath was stripped back inside the junction boxes.

Not sure about the exact cable run. It's a very, very large garden with a stream and bridges, and the cable is buried in places but most of the buried cable seems to be under flagging, concrete or stones around the border.

Quite a few questions and concerns about this. Don't really feel that comfortable with the job, but that may change as I gain more knowledge about it. We're supposed to make the best of the situation, but at the moment I'm not sure it could be done safely and to regs given the stated situation.

Some questions -

1- Is this sy cable ok for use on garden lighting under these conditions instead of swa?

2 - Even though an internal conductor is used for the cpc, does the steel wire braiding also need to be earthed in addition to this, or was the other guy right to just tape it and have no earthing of the braid?

I know swa needs earthing even if an internal conductor is used as the cpc, though I'm not sure why this is the case. Is it purely for shock protection in the event of damage, or does it have anything to do with induced voltages? And does this also apply to the braided armour on this sy cable?
-

I'm also not even sure the guy installed the correct size swa power cable for the length of the ring if it's to be on a 16a breaker like I'd want it to be. At least not according to my quick voltage drop calculation. But he did install swa on that circuit and seems to be terminated and earthed correctly, assuming he used weatherproof glands. Anyway, that's a different post for later.


Any help would be appreciated.

 

[Deleted member 9648]

The situation - Cables were laid in a customers garden ready for lighting and power installation a few years ago by some other electrician but never finished. We've been called in to finish the job. As a trainee, I've been told by my boss to try and figure it out before work commences, but I have some confusion.

Looking at the lighting cable that's been installed, it looks like sy cable - transparent flexible cable with steel wire braiding. It wasn't connected into the ip junction boxes correctly as they all had water in them. All the cables have water damage to an extent - mould getting inside the ends to various degrees under the sheath and some discolouration/rust on the braiding in places. The cable still tests ok.

Looking at the way the cable was terminated at various boxes, an internal conductor was used for the cpc, and the steel braiding was not earthed. The braiding just had tape around it where the sheath was stripped back inside the junction boxes.

Not sure about the exact cable run. It's a very, very large garden with a stream and bridges, and the cable is buried in places but most of the buried cable seems to be under flagging, concrete or stones around the border.

Quite a few questions and concerns about this. Don't really feel that comfortable with the job, but that may change as I gain more knowledge about it. We're supposed to make the best of the situation, but at the moment I'm not sure it could be done safely and to regs given the stated situation.

Some questions -

1- Is this sy cable ok for use on garden lighting under these conditions instead of swa? Probably not buried direct,should be in a duct IMO.However as it's already there a judgement call needs to be made as to whether it is adequate. Is there any warning tape over it?

2 - Even though an internal conductor is used for the cpc, does the steel wire braiding also need to be earthed in addition to this, or was the other guy right to just tape it and have no earthing of the braid?Needs earthing as the braid is a conductive part

I know swa needs earthing even if an internal conductor is used as the cpc, though I'm not sure why this is the case. Is it purely for shock protection in the event of damage, or does it have anything to do with induced voltages? And does this also apply to the braided armour on this sy cable?As stated,the SWA/braid is a conductive part,and therefore requires earthing. A conductive part is defined as a part of the electrical installation capable of carrying current but which would not normally be expected to be live.
-

I'm also not even sure the guy installed the correct size swa power cable for the length of the ring if it's to be on a 16a breaker like I'd want it to be. At least not according to my quick voltage drop calculation. But he did install swa on that circuit and seems to be terminated and earthed correctly, assuming he used weatherproof glands. Anyway, that's a different post for later.


Any help would be appreciated.

.........

 

[Farmelectrics]

Is braided cable correct for this install as it doesn't give the same mechanical protection as swa not 100% sure just asking

 

[Guitarist]

No way that I'd connect SY cable underground unless it's mechanically protected (ducted), is at the correct depth, and has warning tape.
Sounds like it all needs ripping out and redoing.

 

[Spoon]

Have to agree with Guitarist.

Just out of interest: How many light is the cable powering? What wattage are the lights? What size & length is the cable?

 

[Darkwood]

SY is not suitable for this set-up and should not be re-connected

SY is not UV tolerant.
SY braiding is a screen not an armouring and doesn't provide the necessary protection in your case.
SY Braiding requires earthing but should not be used as the earth if used for LV power.
SY suitable glands should be used.

The condition of the cable already reflects its poor installation methods and unsuitability for the job i would be informing your customer its poor quality of work and cannot be re-instated.

 

[Guitarist]

Just out of interest, if your boss has told you to suss this out, be he/she will ultimately make the decision, is there any point us giving our opinions? Surely, as a trainee, you should be learning from the one responsible for your training....

 

[Spoon]

Surely, as a trainee, you should be learning from the one responsible for your training....

But that is logical and we all know that its not about the right or wrong way to do things but 'How much it costs'....

 

[Guitarist]

But that is logical and we all know that its not about the right or wrong way to do things but 'How much it costs'....

Just seems odd to me that any "boss" would take a trainee on a job, then send him away to figure out the job, giving said trainee a few days to ask on an internet forum.
I'd have expected something along the lines of "what do you think", while at the job site, followed by what the boss thinks.

 

[Engineer54]

SY is not suitable for this set-up and should not be re-connected

SY is not UV tolerant.
SY braiding is a screen not an armouring and doesn't provide the necessary protection in your case.
SY Braiding requires earthing but should not be used as the earth if used for LV power.
SY suitable glands should be used.

The condition of the cable already reflects its poor installation methods and unsuitability for the job i would be informing your customer its poor quality of work and cannot be re-instated.

I'm with Darkwood 100% on this one!! But as Spoon quite rightly points out, that it's more about money/costs than any other factor!!

 

[Spoon]

Just seems odd to me that any "boss" would take a trainee on a job, then send him away to figure out the job, giving said trainee a few days to ask on an internet forum.
I'd have expected something along the lines of "what do you think", while at the job site, followed by what the boss thinks.

WOW That is a really radical concept.... Doing the right thing.... I dont think its going to catch on though Guitarist.

 

[GMjohn]

.........
1- Is this sy cable ok for use on garden lighting under these conditions instead of swa? Probably not buried direct, should be in a duct IMO.However as it's already there a judgement call needs to be made as to whether it is adequate. Is there any warning tape over it?

I didn't look that closely at the time. The places it's buried appear to be mostly under flagging and concrete. I think one of the 4 lighting cables may go under grass/soil, but the other 3 don't. I'd have to ask about how they've been buried.

If it's not in ducting, what kind of things would make the judgement call ok to use it? My thinking currently is it would mostly be ok as it is seemingly buried where no digging would take place. But maybe that just illustrates I don't have enough knowledge/experience to make such a judgement call. And the replies so far seem to support that.

Also, when it's clipped direct above the surface, Some of it is within reach of small animals. Is it adequately protected from this? Is this one of the dangers of the braiding being unearthed?

2 - Even though an internal conductor is used for the cpc, does the steel wire braiding also need to be earthed in addition to this, or was the other guy right to just tape it and have no earthing of the braid?Needs earthing as the braid is a conductive part.

I know swa needs earthing even if an internal conductor is used as the cpc, though I'm not sure why this is the case. Is it purely for shock protection in the event of damage, or does it have anything to do with induced voltages? And does this also apply to the braided armour on this sy cable?As stated,the SWA/braid is a conductive part,and therefore requires earthing. A conductive part is defined as a part of the electrical installation capable of carrying current but which would not normally be expected to be live.

I thought it was exposed conductive parts that needed earthing. I wouldn't have considered this exposed as it's got insulation around it. So it needs earthing because it's a conductive part of the installation that could become live under fault conditions. It has no relation to induced voltages, which I was thinking could be possible from my memory of theory a while ago?

To help me try and understand at a deeper level from my current understanding of earthing, what's the likely dangers from this braid not being earthed? if it's buried, what dangerous situations could occur from this, especially if it's not buried in areas where digging would usually take place? It's easy to think of the dangers that can occur from exposed conductive parts not being earthed inside a property or at accessories, but I'm struggling to think of examples in this situation. Is it if it becomes live under fault conditions and then a person or animal cuts through the outer sheath, they get a shock - but then wouldn't the rcd trip and protect them? Is it something else?

 

[GMjohn]

No way that I'd connect SY cable underground unless it's mechanically protected (ducted), is at the correct depth, and has warning tape.
Sounds like it all needs ripping out and redoing.

I don't think ripping out is an option as it's all been landscaped etc. Option is to get anything we can connected and installed so it's safe and to regs, or not at all. At least that's what I'm thinking having never spoken to the customer.

I have no idea if it's ducted. It seems buried in areas where no digging will occur - under flagging and concrete. Only one of the 4 lighting cables could be under soil or a garden, but it may be under the stone pathway. I think the gardener and owners will have knowledge of this, so I'd have to ask.

Have to agree with Guitarist.

Just out of interest: How many light is the cable powering? What wattage are the lights? What size & length is the cable?

The guy installed 4 separate cables, each one between 30-45 meters in length. 1.5mm cable. Actually, it was mostly 2.5mm cable, but a small part of it was 1.5mm, so i've downgraded it all to 1.5 to be on the safe side. These distances include 10m of 16mm swa distribution cable.

One cable has just one light on it at the end. The others have 5 or 6 points on each of them. There were no actual lights, just junction boxes for the lights to run off, so I allowed 100w per light for any calculations I did. Using 6 100w bulbs on the longest cable run of 35m plus 10m distribution cable, I think I calculated voltage drop at 2.6v on the light cable and 0.7v on the distribution cable, (used total design current of 24a when calculating vd of distribution cable), so 3.3v total voltage drop for the lighting cable.

The way the guy's installed the cable is that he's run 10m swa distribution cable from the garage to the back of the house. He's then run 4 sy cables under the patio flagging at back of the house, about 15m. They are cut off here, possibly with damaged ends, but probably enough slack to cut it back. He's then run 4 more sy cables in different directions, another 10-20m each. Either under stone pathways or clipped direct. 2 of the cables have no junction boxes or lights installed. Just cable, with loops where it's to be terminated with an accessory.

I was thinking if it was possible to combine these four circuits into fewer, for switching purposes. So they'd be a 10m distribution cable run, followed by around 15m of the circuit run under the patio, where it would then radiate out 2 or 3 directions, all around another 10-20m each. However, I'm not sure how this changes the voltage drop calculation when a circuit radiates like this. I can make an educated guess, but I've not found confirmation of the right way to do the calculation when a circuit radiates in different directions from one point.

SY is not suitable for this set-up and should not be re-connected

SY is not UV tolerant.
SY braiding is a screen not an armouring and doesn't provide the necessary protection in your case.
SY Braiding requires earthing but should not be used as the earth if used for LV power.
SY suitable glands should be used.

The condition of the cable already reflects its poor installation methods and unsuitability for the job i would be informing your customer its poor quality of work and cannot be re-instated.

It's looking that way based on the posts so far.

Would black insulation tape around the exposed parts of the cable be suitable or adequate to give it uv protection?

If so, and the buried parts turned out to be ducted, an internal conducter used for earthing, and suitable glands were used to connect it to the plastic ip rated boxes so the braid was earthed, would it then be ok to use?

If the buried parts turned out not to be ducted, but buried under concrete or paving, would that be ok?

I assume parts of the cable ends which have had water get into them and mould or discolouration/rust of the braiding has occurred should not be installed. If so, this isn't in every part of the installation. If there was enough spare cable to cut the water damaged ends off, and/or cut out parts of the installation where that damage has occurred and can't be cut back, ending up with a smaller circuit with none of that damage in the cable ends, would that be acceptable?

Just out of interest, if your boss has told you to suss this out, be he/she will ultimately make the decision, is there any point us giving our opinions? Surely, as a trainee, you should be learning from the one responsible for your training....

I will learn from him, but I like to develop a deeper understanding of the underlying knowledge rather than just know what to do. I can only ask him so many questions before I start to feel like I'm pushing my luck and becoming a pain. It also helps to get different viewpoints from other experienced electricians. For all I know, I could be picking up bad habits.

Personally, I like to be able to do prep work when there's an opportunity. I think looking into things ahead of time will help me learn and develop quicker.

I'm with Darkwood 100% on this one!! But as Spoon quite rightly points out, that it's more about money/costs than any other factor!!

Does that mean some electricians in this situation, for cost reasons, would still do the job as is even if the sy cable wasn't installed properly - buried cable with no ducting or poor condition ends or unearthed braiding etc? Wouldn't that be dangerous? Or did I read your post wrong? Makes me curious what my boss will do in that case.

 

[Guitarist]

Does that mean some electricians in this situation, for cost reasons, would still do the job as is even if the sy cable wasn't installed properly - buried cable with no ducting or poor condition ends or unearthed braiding etc? Wouldn't that be dangerous? Or did I read your post wrong? Makes me curious what my boss will do in that case.

You have been given our opinions, and most of us here aren't the "that'll do" brigade.
The only way in which I would use this cable, is if I was running ELV down it.

 

[Darkwood]

As above 230v forget it .... wrapping black tape over it now your really talking cowboy land its not designed 'period' for the use in your situe' i can't comment how the external environmental clear sheath will cope to external influences only the manufacturer can tell you this but its not designed for this set up so stop clutching at straws and get the job done correctly.

 

[Engineer54]

Originally Posted by Engineer54
I'm with Darkwood 100% on this one!! But as Spoon quite rightly points out, that it's more about money/costs than any other factor!!

Does that mean some electricians in this situation, for cost reasons, would still do the job as is even if the sy cable wasn't installed properly - buried cable with no ducting or poor condition ends or unearthed braiding etc? Wouldn't that be dangerous? Or did I read your post wrong? Makes me curious what my boss will do in that case.

I would like to think that qualified and knowledgeable electricians wouldn't entertain using this SY cable in an external environment that you have described. As has been stated, the cable is totally unsuitable for these environmental conditions, especially from the mechanical protection it offers and to it's lack of UV protection!!!

 

[Deleted member 9648]

I thought it was exposed conductive parts that needed earthing. I wouldn't have considered this exposed as it's got insulation around it. So it needs earthing because it's a conductive part of the installation that could become live under fault conditions. It has no relation to induced voltages, which I was thinking could be possible from my memory of theory a while ago?

To help me try and understand at a deeper level from my current understanding of earthing, what's the likely dangers from this braid not being earthed? if it's buried, what dangerous situations could occur from this, especially if it's not buried in areas where digging would usually take place? It's easy to think of the dangers that can occur from exposed conductive parts not being earthed inside a property or at accessories, but I'm struggling to think of examples in this situation. Is it if it becomes live under fault conditions and then a person or animal cuts through the outer sheath, they get a shock - but then wouldn't the rcd trip and protect them? Is it something else?

An exposed conductive part is simply defined as a conductive part which can be touched.....on an SY cable it would be almost impossible to completely remove the possibility of touching the braid or a gland at terminations. Same principle as a flush metal backbox.

 

[davethsparky]

OP

I think you'll find there is a line in the book that requires buried cables to have an earthed metallic screen or armour, that might just be a good reason why you'd have to earth the screen!

 

[Spoon]

I think you'll find there is a line in the book that requires buried cables to have an earthed metallic screen or armour, that might just be a good reason why you'd have to earth the screen!

Do you mean 522.8.10

 

[telectrix]

the main point of earthing the armour/metallic braid/whatever is so that if the cable were to be penetrated by nail/screw.spade/whatever and said penetrating metal object was to contact with the "Live" conductor, it would also be in contact with the earthed shield and therefore cause operation of the OCPD. if it's not earthed you end up with a live armour and tool. not the best scenario.