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 Question by Marc Cushman posted 09 May 2006
I was very recently added to the decision-process for the cabling/computer portion in the construction of a new facility. One of the contractors asked me about the conduit that is already IN the foundation, he wanted to know if the 1" pvc will be sufficient for the CAT6 that will be used for all voice and data run to each office. Each "drop" will have 2 voice and 2 data cables. I have tried to search EIA and TIA websites but cannot seem to find the actual standard. The maximum distance to the farthest office is approx 175', +/-5'. I saw in a few other quesitons you answered that it cannot exceed 90', was that for any conduit, or outside only? Thank you in advance.
 Answer by Dmitri Abaimov posted 09 May 2006
Dear Marc,

the 90' rule actually comes from the TIA/EIA-569-B standard and it is applied to INSIDE conduits. The standard is, however, not a code. That is: it is designed to guide you in your efforts to build a system that would perform at its best. If the real life circumstances go against the standard, you can deviate from the standard to work around the obstacle. You should obviously recognize the fact that if you deviate too far the system may not work at all, but the point is: it is up to the designer of the system to decide if the standard requirements can be met. Unlike the code compliance whereby deviations may cost the customer penalties, delays and potential insurance problems.

So with that said, if the 1" conduits are THE ONLY way to deliver the cable to where it needs to be, then the 1" conduits are THE way to deliver the cables. Then your problem will be to calculate how many cables can you pull through a 1" conduit, and I can tell you that it is not going to be too many. Use this conduit fill capacity table and lower the amount of cables to about half of the original amount for longer conduit runs. Obviously consider if the conduits have bends, how sharp those are and whether or not there are already cables or other possible obstacles inside the conduits. In extreme cases you may need to abandon some of the conduits, so be prepared.

Dmitri Abaimov, RCDD

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