European style cable G and B

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jes25

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Gentleman, I am working in overseas environment where the NEC is used for reference only. I have been asked to asses some of the grounding and bonding. One of the primary wiring methods is using European style armoured cable such as that produced by Gulf Cable & Electrical INd. Co. This cable has insulated copper conductors surrounded by stranded steel armour and covered with a PVC jacket. There is no EGC inside the cable. I was wondering if anyone could help me on the intended use and proper termination of this armour as I am unfamliar with the cable and any associated standards. Is the armour acceptable to be used as an EGC such as EMT is in the US? Is it only to be bonded on one end to clear faults in the cable and an external EGC routed with the cable? Is it permitted to cut some of the armour strands if used as an EGC?

Any help at all would be greatly appreciated. Any links or leads to any standards would be fantastic.
 
You are describing cable known as SWA, for Steel Wire Armoured. It's widely used in many circumstances where mechanical protection is required, and it's a lot quicker to install than conduit. Panelboards in commercials or industrials will almost universally be fed from the main board using SWA. It can be used outdoors and underground directly. Available in a number of sizes (measured in sq mm) and in up to seven cores, though larger cables typically only available as three or four core. You can parallel them as required.

Heres a link to a UK supplier with pictures. If you click on the part number you get to the accessories needed to terminate this cable. It's essentially a clamp that clamps down 360 degrees on the armour.

Yes, it is armouring will always be earthed (you're in Europe now!), and is usually the ECC, unless there is some reason not to. For example computer rooms usually use an extra core for earth, but even then the armour is still earthed, it's just not the earth conductor for the load.

There are tables in the back of the wiring regs giving charts for length versus resistance etc so you can select the correct cable for the job. Unless something has changed recently, the rated load is the rated load, no need to do the NEC 80% continuous de-rate thing.
 
Thank you for the reply. Let me first say I actually am not in Europe. I am on an American installation in the middle east. There is a lot of temporary style work. It is common practice to not use the brass glands and just twist up about 1/4 of the Armour strands and use them for the EGC. I take it I am correct in saying this is unacceptable to use only part of the armour at the termination.

I have noticed several panels with feeders installed with no EGC and the armour trimmed off, rendering the panel unbonded to the system neutral. In other words using a gnd rod and the surrounding dirt as the only fault current path. In the USA this is of course unacceptable and a shock hazard. However most of the main breakers here have 300 ma GFP protection. This leads to my next Q: Do Eurpoean Grounding or Earthing systems rely on dirt as the fault current path and assume the 300 ma GFP will open the circuit in a fault situation?.........or ...........am I just seeing improper installs by incompentent or untrained individuals? I think the latter.

and 1 other thing. Whats up with the single core armoured wire. Would that not cause magnetic heating, like it would if you installed 1 wire in a steel conduit?


Thanks agian for any help?
 
jes25 said:
It is common practice to not use the brass glands and just twist up about 1/4 of the Armour strands and use them for the EGC. I take it I am correct in saying this is unacceptable to use only part of the armour at the termination.
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It's bad, you are correct, terrible installation practice.

jes25 said:
Do Eurpoean Grounding or Earthing systems rely on dirt as the fault current path and assume the 300 ma GFP will open the circuit in a fault situation?.........or ...........am I just seeing improper installs by incompentent or untrained individuals? I think the latter.
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No they dont, and correct. Well, amost. European installation practice is pretty much the same as American practice, ie using the TN-C-S earthing style. Sounds like what you have there is a TT system, which is a permitted (but rare) scheme, but does need RCDs as the fault current wont trip breakers under earth fault conditions. It's permissible, but ugly. Also 300mA RCDs wont save anyone's lfe.

As an aside, if there are any 110V transformers there (fitted with yellow C17 sockets) then there is a real danger if they are not earthed properly - no time to explain now, but if they come up, mention it.

jes25 said:
Whats up with the single core armoured wire. Would that not cause magnetic heating, like it would if you installed 1 wire in a steel conduit?
Click to expand...

Yes, you are correct, but in reality you would never install SWA in conduit. It's usually done using standoffs on tray or off Unistrut. Generally folks install multiple three or four core cables in parallel rather than use big singles.
 
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Thanks again for the help. What do the acronyms stand for? RCD, TT T-N-CS?

Yes agreed 300ma RCD (aka GFI in the US) wont save anyones life.

Thanks again.
 
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