Derating buried armoured cable


Old 07-27-14, 10:44 AM
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Derating buried armoured cable


Having moved into a house I have an armoured buried cable out to the shed which I plan to use as a workshop. I wanted to check that I have the correct fuse(breaker) rating as the current 40A rating sounded too high. I found the manufacturers specs for the cable which state a current rating of 32A, so the current rating is much too high.

I know that cable in insulating has to be derated, so I thought that buried cable does as well, but my local Part P electrician just gave me a blank look.

Anyone got any info...pointers..hints..rumours?

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Old 07-27-14, 10:52 AM
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Most armored cable isn't rated for direct burial. What kind do you have? Why armored cable in the first place? Normally you would use UF direct burial cable or PVC conduit with individual conductors. You failed to fill out your profile. Please add your location so we can better help you.
Old 07-27-14, 11:06 AM
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Part P electricians are found in the UK.

I'm not familiar with a bury-able armored cable either.
Old 07-27-14, 11:13 AM
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Hi. Thanks for the response. I am in the UK.

The cable is SWA 3 core and is the standard method of laying cable in the garden in the UK.

I will find a UK forum for members more familiar with UK wiring practice. Thanks for your responses.
Old 07-27-14, 02:27 PM
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The only metal sheathed cable I am aware of that can be direct buried is PVC jacketed MC cable. It can also be installed in poured concrete. I know nothing about any SWA 3 core cables, whatever they are.
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