SWA armour supply to outbuilding, what CSA cable? and Reference Method?

[dinger809]

What fire are you predicting here? 6mm SWA has a ccc of 49A single phase clipped direct at an ambient temperature of 30c which is well above the nominal current of the circuit.

Ok, bad turn of phrase, I wasn't saying this would start a fire. The point I was trying to make is that if you do a calculation according to the BYB stick to what it says, dintbthen second guess it. That is your safety net. If you stay with that, then nothing should go wrong and if it does, you can always say, I followed BS 7671 to the letter and you are fully covered.

 

[Dave OCD]

that will look smart nailed on his £50/roll wallpaper.

Do they use that round your way on the outside of houses Tel ??

 

[Sparky_marky2]

At 30m the volt drop would exceed the permitted maximum though..(going by the book)....though in practice we all know 6.0mm would be perfectly OK.

I know right this is what i've been taught from sparks i've worked with on site, "6mm does that job" but now im doing the jobs on my own i find myself questioning what I've learnt a lot more....

 

[Sparky_marky2]

yeah, but OP has used 40A for his Ib. in practice 25 - 30A would be more realistic.

Do recommend dropping the MCB size? I had thought about 32A

 

[Sparky_marky2]

40A through 6.0mm SWA is well within it's capacity. that's why i said 10.0mm was overkill.

Thanks for the reply Telectrix always appreciate your input

 

[Richard Burns]

Do recommend dropping the MCB size? I had thought about 32A

I do not think dropping the MCB size is the intent it is mainly using the expected design current for the calculation rather than the maximum current the MCB can take.