Hep with chalet installation

[bbbbbb]

right, there is a 2-core 4mm swa leading from the CU in the house to a chalet 5m away. The chalet has two circuits, lighting on a 6amp breaker and two socket radials on a 16 amp breaker.

is it okay to use the steel sheathing from the swa as the earth?

should be on a 20 amp breaker at the house right?

 

[Zeespark]

What are earthing arrangements like on both the house and chalet side of the installation, TT? TNS?

AndyGuiness Drink

 

[binky]

Nothing wrong with using armour as earth, if not common practice anymore. 4mm will take 32A - check your OSG or big red book, allowing for volt drop of course.

 

[bigclive]

4mm will take 32A - check your OSG or big red book, allowing for volt drop of course.

Are you sure about that? We were just contemplating downrating a circuit breaker from 32A to 20A on the basis that part of a job has a short (8m) length of 4mm four core SWA leading from the main DB to an isolator where it jumps up to 6mm for the rest of the run. I was under the impression that 4mm is only rated up to about 28A, but if it's fine for 32A then that would save changing that breaker. I'm going to have to check that up now.

Of course I could change that section of cable, but it's a fairly low priority area of the job.

 

[Andy™]

4mm SWA is rated 41A method E, 37A method D

 

[binky]

25A MCBs are also available in certaim makes. But if you don't trust my figures look them up in the big red book as Andy has.

 

[jl-heating]

what about earthing the swa in the house and not terminating in the chalet board.

then tt the chalet ?

 

[binky]

No mention of water-pipes, so debatable as per exported earth posts.

 

[bigclive]

4mm SWA is rated 41A method E, 37A method D

Now that you mention it, and more importantly now I've gone and had a look it does appear that the 4mm is adequate for the application. It's method C and the rating for 4mm 4-core does exceed 32A. (42A on the chart I just consulted.) That means that all I need to do to that part of the job is improve the earthing by popping some earth bolts through the frying pans on the existing glands and giving it a test.

For some reason I thought 4mm was rated 28A. My apologies to Binky for doubting him.