Can we use the armour of an SWA as the CPC???

[Engineer54]

In respect to the above posts,, I never take the earth from a property out to an external area, garage shed etc. even though as you say a good Zs from a TN system is a lot better than a high Zs on a TT.. the taking of one earth potential ( the house) to an external area such as the garage can cause (and I have seen it) a potential diffrence..

my main aim when wireing to out buildings is keeping any fault current/ voltage below 50v and appropreate disconection times. Ive seen lost neutrals on PME systems where outhouse neutrals and earths have become live to the surounding earth... would hate to step out that hot tub bare foot onto tera firma.. but hey thats me.. and I know this argument has been done to death, but ive seen the consequences of taking earths from diffrent areas and felt the potential diffrence!!!! :rolleyes4:

im not starting an argument... its just what i feel,, and as long as we are safe and follow the regs,, then we all win!!

I would just love to hear your argument for leaving a TN-S earth behind, in favour of a crap UK TT Ra value??

I'm not getting into the PME argument here, but i sorely disbelief you've seen a full broken neutral, if you have you are amongst the very few that have!! I have a very good friend that has just retired from your area's DNO, he's been with them and the old Regional leccy boards since leaving school, and retired as a Regional Manager. .....He has only known of 3 such instances in all that time, all were tripped out by there protection relays...

As for the ''hot tub'' senerio, you make allowances/provisions in your earthing arrangements when this is a factor in your installation. The truth is here though, how many hot tubs have you seen in the back yards of housing estates, ...not many i would think. Common as muck mind in Cyprus among the Brits...lol!! Now think about it, ..what do you think would be needed if a house owner foolishly locates a hot tub on his lawn, and not on a substantial base, patio, or Decking??

One last thing, in certain parts of Essex, i would agree with you, using a rod, because in those area's that i know of, i know that i can get better than a TN-S earth, with a couple of rods coupled together. lol!!! Yes, i know Essex very well!! lol!!

 

[ZsElectric]

So you think a rod is better than a TN system earth do you?? .....Then your a fool !!!
The mind just has to boggle at some of the completely daft an ill informed statements such
as this one.

well thanks for your kind remarks I thought this site had a no rudeness policy?
For someone who is supposed to be a "respected member" I am shocked at your attitude as you don't know all the facts the whole system is a TT and maybe I didnt explain all of the details of this situation climb down off your high horse, an apology would be appreciated Mr respected member (snyde)

 

[ZsElectric]

you know what forget it I don't want to associate myself with you or your self congratulatory site at all, what a warm welcome and what a riddiculous waste of my time you have proved this to have been

 

[Edd]

I would just love to hear your argument for leaving a TN-S earth behind, in favour of a crap UK TT Ra value??

I'm not getting into the PME argument here, but i sorely disbelief you've seen a full broken neutral, if you have you are amongst the very few that have!! I have a very good friend that has just retired from your area's DNO, he's been with them and the old Regional leccy boards since leaving school, and retired as a Regional Manager. .....He has only known of 3 such instances in all that time, all were tripped out by there protection relays...

As for the ''hot tub'' senerio, you make allowances/provisions in your earthing arrangements when this is a factor in your installation. The truth is here though, how many hot tubs have you seen in the back yards of housing estates, ...not many i would think. Common as muck mind in Cyprus among the Brits...lol!! Now think about it, ..what do you think would be needed if a house owner foolishly locates a hot tub on his lawn, and not on a substantial base, patio, or Decking??

One last thing, in certain parts of Essex, i would agree with you, using a rod, because in those area's that i know of, i know that i can get better than a TN-S earth, with a couple of rods coupled together. lol!!! Yes, i know Essex very well!! lol!!

Seen it 4 times 1 six months ago in canvey,, seen flexy hoses under a kitchen sink blow apart when they used the shower!! seen the metal frame of a garage sitting at 230v where neutrals have gone down.. and they NEVER trip the RCD.. it only takes one broken neutral to kill someone.. and one is one to many.

I used to contract to the Eastern Electricity Board years ago.. so yep I know the area well... But as Lenny said lets leave it there..
Oh wait just remembered a row of terraced houses in basildon owned by the commision for new town (years ago) about 5 places were complaining of shocks... turned out that the first in the row had lost its neutral!!

I totally agree TN systems are much better and saffer in propertys but IM fully aware of the issues of taking them outside!! as Lenny said this aint the place for this discussion.. But you really do seem to be set in your ways when it comes to TT systems..

Tell the truth im a plumber and im making it all up. yep ive never seen a neutral go down wouldnt know what to look for. I say sod the earths and just tie all neutrals and earths together, then theres no argument.. earth whats that?? all i know its what i dig my garden flower in

 

[Guest123]

you know what forget it I don't want to associate myself with you or your self congratulatory site at all, what a warm welcome and what a riddiculous waste of my time you have proved this to have been

TBH, a first post telling the majority they 'cut corners' & take chances' for an 'easy life' isn't the best way to ingratiate your way on an internet forum.

Whilst some members may have an 'abrasive' way of getting their point across albeit valid, everyone is entitled to their opinions. This is what forums are about, someone makes a post, someone else replies with a different view and so on etc.

It would be a very boring place if everyone agreed with each other.

 

[Engineer54]

Seen it 4 times 1 six months ago in canvey,, seen flexy hoses under a kitchen sink blow apart when they used the shower!! seen the metal frame of a garage sitting at 230v where neutrals have gone down.. and they NEVER trip the RCD.. it only takes one broken neutral to kill someone.. and one is one to many.

I used to contract to the Eastern Electricity Board years ago.. so yep I know the area well... But as Lenny said lets leave it there..
Oh wait just remembered a row of terraced houses in basildon owned by the commision for new town (years ago) about 5 places were complaining of shocks... turned out that the first in the row had lost its neutral!!

I totally agree TN systems are much better and saffer in propertys but IM fully aware of the issues of taking them outside!! as Lenny said this aint the place for this discussion.. But you really do seem to be set in your ways when it comes to TT systems..

Only the crap that the UK calls a TT system!! Nothing wrong with a good TT system at all!!

Oh and by the way, Canvey, Basildon, was well and truly in my friends area, so i'll say no more on that one!! lol!!!

 

[Engineer54]

I recently found an swa used in this way to a garage, personally in such a zone I would never try to use the sheathing and so installed a rod to earth the satellite box, maybe I dont like to cut corners but then I never take chances just for an easy life

Sad as it may be, we are not unfortunately mind readers!! So if i have upset your feelings somewhat i wholeheartedly appologise.

If this was TT system, then surely it would have been prudent to install another rod at the garage anyway, and used the armouring of the SWA cable to link the two rod positions via the MET

The whole point of this particular thread is to dispel the myths, that the armouring of SWA should NOT be used as the circuits CPC. Now if you think otherwise, that's another matter entirely!! lol!!

 

[ZsElectric]

I used poor language when I was mistakenly accused of claiming that people on here cut corners or took chances I would never accuse anyone of that unless I saw it for my own eyes, incidentally as I did today (another story).

What was meant by that was that in this instance was that if I had used the sheathing I would have been cutting a corner and I would have felt that I was taking a risk, due to the way the SWA had been installed and when installing a rod was a better method, there's nothing wrong with a TT system its well within tolerance and as the board has an RCD which trips well within 20ms on the rod why not. I accept your apology for hurting my feelings as I hope you will accept mine for not explaining myself in a fuller and more concise manner.

 

[Guest111]

only on Thursday I got a call to a fault on a concrete mixing plant. turns out the fault was on a motor on an external belt which brings the sand to the mixer. when I went to the motor a discovered that the only earth to the motor was the steel armour. this had rusted away comletely. therefore the motor had no earth. then I felt I better check the rest of the motors. found another the same and one more on its way out. its reasons like this why I don't like using the armour.

Hey Hawk just had a blinder at work,boss opens control panel as there is a puddle below it,rings me and says that there is water coming out of an armoured cable,anyway I go to look and yes he,s right turns out previous spark who installed kit has used a dodgy isolator 40 foot up on a conveyor outside,made me look good though I knew it had to be a high up cable as it had run over 20 foot horizontally.

 

[g-davies]

All the comments were great,every time my boss is sizeing swa for a job,he always asks can the armouring be used as cpc.I will show him these ta

 

[Engineer54]

Here's a link to a site with relavant CSAs for both 70 degree and 90 degree armours:
steel wire armour as the earth conductor
The site has a number of downloads that may be usefull.

All the comments were great,every time my boss is sizeing swa for a job,he always asks can the armouring be used as cpc.I will show him these ta

The table's shown in this link is what you need to show your Boss!!

 

[micknew]

We use Amtech software and have never had the swa armour fail as a suitable earth conductor.
We specialise in domestic and heavy industrial installation work.

 

[Engineer54]

We use Amtech software and have never had the swa armour fail as a suitable earth conductor.
We specialise in domestic and heavy industrial installation work.

That would depend on size and core number, it would also depend if your program automatically undertakes adiabatic equations in it's calculations. But it's not always the case where the SWA will meet the cables requirements of being the CPC...

Where figures work out, that are right on the knuckle so to speak, you may have to look at the length of that cables run....

 

[Jeffmo65]

Hi folks very interesting post which provokes a lot of thought and reading / interpretation . I was once installing cabling for a large banking organisation for some UPS feeds , at that time we had our NICEIC assessment . Particularly he picked up on the fact that we had ran seperate CPC for the majority of the cabling installed , we stated that as a matter of belt and braces we installed these seperate CPC . At the time he informed us that anything less than 10mm2 (SWA) requires seperate CPC , so theoretically the seperate CPC installed by us was not required , but possible good practice .

 

[Engineer54]

Then the NICEIC inspector was clearly WRONG!! The Steel wire armour of the smaller SWA cables are more than adequate to be used as the circuits CPC. It's only after 95mm that you need to check for compliance!!

Things are a bit different if your intending to use the SWA for bonding purposes. As the SWA then needs to meet the copper equivalent of the required minimal bonding conductor size related to that installation...