Horrible thought

[David E]

Have just had a look at the end of the 3 core swa cable that has just been buried and spotted although it is for a single phase installation, the cores are brown, black and grey isn't this 3 phase cable? I know I should have checked, but as usual didn't. Have I got a big problem?????

David

 

[plugwash]

whilst you can get brown/blue/green+yellow 3 core SWA its rare and expensive

just make the cores appropriately with tape or sleeving.

there is some controvisy on which way round to do neutral and earth so marking this up is far more important than under the old codes.

 

[Adam_151]

Thats the way 3 core SWA is coloured, just sheeve the ends accordingly

use brown for live
use grey for neutral and sheeve it blue
use black for earth and sheeve it green/yellow, as you would on bare t+e earth stand.

There is an arguement (that I agree with), that it should be the black used for the neutral, however NICEIC have started to create a de-facto standard of grey for neutral, and in the absense of any other group having an opposing standard, its probably best you go along with it, standards should be allowed to develop

 

[David E]

Phew. A great weight has been lifted!!!!!! It has been one of those days. Digger cut through a live 10mm SWA cable - blew the REC fuse , leak in the bathroom.....

Just a thought when I was looking around the forum for what to do with blown fuse, noticed (but already knew) that removing the seals and crimps shouldn't be done, looked in the outside meter cabinet to see that the paper seals were missing then realized the reason was the numerous snails in the cabinet had eaten them!!! I have noticed before that snails do eat paper but I recon this is a good excuse to give if you get questioned as to the location of the paper seals. Just make sure you remove the paper completely and chuck in a few snails - not that I would ever dream that any one would do this of course!!!

David

 

[plugwash]

since outside meter boxes can be opened by anyone with a meter box key (which really aren't hard to get and you could probablly do it wihout one anyway) its going to be pretty damn hard to prove who broke the seals anyway

meter boxes are really only designed to keep out kids drunks animals etc not and adult with presence of mind and a toolbox

really if you blow a service fuse you should call the rec/dno but if you have a spare its less hassle for everyone including them if you just replace it.

 

[BenStiller]

whats all this about paper?

 

[Adam_151]

Isn't there something wrong here?

10mm SWA cable, whats it going to have on the end of it, probably a 50A, B or C breaker, shouldn't there be enough descrimination between this and a HRC service fuse (esp. if its a 100A one)

Unless its just connected through a switch fuse to the tails?, then its understandable

 

[plugwash]

i can imagine discrimination between say a 45A hrc and a 60A service fuse wouldn't exactly be brilliant

otoh if that 10mm cable was on a mcb then it seriously sounds like you have a serious earth fault loop impedance issue.

 

[David E]

The 10mm swa is a spur from after our isolator that supplies our private water pumping system (no mains water here!!).

 

[ban-all-sheds]

Could you describe in more detail the sequence of things you have, (or post a photo), e.g.

service head--meter--isolation switch--cu-- etc?

It sounds as if you're saying that this SWA is connected after the isolation switch and before the CU - if so this is a Bad Thing™...

 

[David E]

It feeds another cu

 

[HDRW]

It feeds another cu

Yes, but it sounds like it's protected only by the service fuse. Apart from the annoyance when it blows it, as just happened, the service fuse may be rated way above the cable, which is a very Bad Thing indeed!

Remember that a fuse (or CU/MCBs) only protects what is beyond it - a fault before it (digging through it is an excellent example) won't blow/trip anything at the far end.

Cheers,

Howard

 

[David E]

See what you mean. Given the length of the cable - 50m and the diameter 10mm, the max current would be around 48A. So 50A breaker should protect the cable before it reaches the CU and also, not that I'm going to do it again, should it br dug up it will not blow the main fuse!!!!!. Am I thinking along the right lines?

David

 

[ban-all-sheds]

No no no!

10mm dia 3-core SWA will be tiny - 1.5mm², which has a rating of 21A.

 

[David E]

Yes, yes, yes.

It's 10mm 3 core SWA cable overall diameter about 3/4".