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Table 4C1

ianlloyd

Just taking Item/row 1 as an example  in Table 4C1 - The way I read it is that for up to 9 cables/circuit, you read the rating factor directly and for 9-11 cables/circuits use 0.5, for 12-15 use 0.45, for 16-19 use 0.41 and for 20+ use 0.38…?

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  • 0

    well yes, but  I'd caution that really by the time you get to bundles that big it is not a great assumption that a single figure applies. Obviously the escape route for heat generated by the  cable in the bundle centre is the limiting factor, and if the bundle is non uniform - perhaps slightly elliptical rather than circular  then the distance from centre to edge is is not the same. You could squeeze a bit more by putting more lightly loaded circuits in the middle.

    In the end the tables are guidance - at some point a measurement is more helpful, and often complex cable routes are such a case.

    Mike

  • 0 in reply to mapj1

    Thanks Mike. Yes, I understand that there are additional heating effects to consider (the Commentary explains in more detail) but I was just wondering about reading the table itself - seems like we are in agreement on that point.

  • 0 in reply to ianlloyd

    well it is not really made clear I agree - I suppose you could plot a curve of the points given to get a more precise, but no more accurate figure for a bundle size not given, but the adjacent value is usually a good starting point.  Personally, I prefer to wrap max indicating temperature stickers into things I expect to run close to the limit, and round bunches of cable are a bad idea anyway -  a 'ribbon' layout on basket is much nicer.if you possibly can or loose to allow free air flow.

    Mike.

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  • 0 in reply to ianlloyd

    well it is not really made clear I agree - I suppose you could plot a curve of the points given to get a more precise, but no more accurate figure for a bundle size not given, but the adjacent value is usually a good starting point.  Personally, I prefer to wrap max indicating temperature stickers into things I expect to run close to the limit, and round bunches of cable are a bad idea anyway -  a 'ribbon' layout on basket is much nicer.if you possibly can or loose to allow free air flow.

    Mike.

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