Current capacity of XLPE SWA

Feb 26, 2006 1 Replies
A

Given that the current carrying capacity of 2.5mm^2 PVC SWA is quoted at =



~23A upto 70=B0C and 2.5mm^2 XLPE SWA is quoted at ~36A upto 90=B0C



I realise that appropriate de-ratings for ambient=20 temperature/grouping/insulation/fixing method need to be taken into=20 account, in this case buried direct with for majority of the run with=20 the final 1m at each end cleated to brick and wooden post respectively,=20 as well as voltage drop over the cable length.



When (if ever) is it appropriate to make use of the XLPE's higher=20 rating, what type of terminals can be judged to handle the maximum 90=B0C= =20 temperature? Do they have to be made from thermosetting rather than=20 thermoplastic material?



How about an adaptable box like=20

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the main breaker terminals of
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in practice is is usual to just treat XLPE as "merely" PVC and use=20 the lower rating?



Also what is an acceptable upper assumption to make for ambient=20 temperature of a shed?


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A

it seems the current capacity of the terminals are a limiting factor at=20

25A, I assume a standard 30A terminal block would not like 90=B0C, so=20 would something like=20
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appropriate?

Or does the temperature problem just transfer (literally) onto the PVC=20 insulated T+E that would be joined at the terminals?

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