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energizedelec

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iv been asked to install a supply to a house and im a bit rusty. can someone please walk me through the cable calculations?

supply is a protected by a 100a bs1361 fuse, cable will be swa installed direct in ground, cable length around 40 mtr.

thanks
 
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Amp David

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Mentor
Arms
Firstly you'll be required to not rely on that 1361 cut out fuse for protection of the supply, so decide on what size you will require.
 
E

energizedelec

  • Thread Starter Thread Starter
  • #3
100a circuit beaker, 25mm SWA ?
 
E

energizedelec

  • Thread Starter Thread Starter
  • #8
ok so after applying diversity Ib = 91.5A and In=100A
so from table 4d4a multi-core armored 70'c refrence method D you get 99A for 25mm cable.

then volts drop mv/a/m = 1.75

so...
1.75 x 91.5A x 40 mtr /1000 to convert to volts = 6.405v

now if it was a final circuit not for lighting this would be ok (as it doesnt exceed 11.5v 5%). but its for a distribution circuit so if i was to then have other circuits running of it the volts drop would increase how do i account for this??
 
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