Cable Length

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 Question by Bruce Harry posted 18 Feb 2004
 Cable Length
I am curious as to what you think is the quickest and more accurate method of calculating the average and total amount of horizontal cabling required for a project? I have heard of several different methods, from as measuring each run to get an average to measuring just the shortest and longest to get the average. Have any studies been done that show a correlation between average cable length and the overall dimensions of a given floor, the number of closets, etc.
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 Answer by Dmitri Abaimov posted 18 Feb 2004
Dear Bruce,

I've found it not very accurate to use the overall dimensions for estimating amount of cable. This may pretty much give you a rough estimate, something like do I need a box or a pallet?
This may suffice in some situations, but in a competitive bid I prefer to break the floor on several zones, grouping outlets into zones based on their average distance from the IDF. Then you would measure the longest and the shortest length to that zone, find the average and add twice the ceiling height to accommodate for up-down drop. Then you would multiply this zone-average length on the number of drop per zone, and at the end sum all the zones that belong to the same IDF. That would give you total length per IDF.
Do not also forget to round up amount of cable needed due to 1000 feet packaging: you can only pull a limited amount of full cable runs from a single box, which leaves you with up to 5-10% waste per box.

If you have multiple IDFs, last step would obviously be to sum all the IDFs for the total project cable length.

Good luck!

Sincerely,
Dmitri Abaimov, RCDD

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