Tim Murphy, RCDD
In "Plan cable runs during rough-in to avoid electrical problems" (see "Installer Tips," April 1996, page 50), I was pleased to see that issues such as commercial power and voice and data cabling were addressed, especially using diagrams. The graphic makes it easier for a new installer to understand what is required and how to do the job.
Drawings should be compliant with the 1996 National Electrical Code NFPA 70 and should follow the EIA/TIA-569 standard recommendations. Because installers may take the drawing as gospel, without finding out what the standard is, it might be helpful to list the appropriate standards on the graphic or mention in the text that these are the standards and not just manufacturer`s guidelines.
For example, the EIA/TIA-569, Section 10.4-1 standard on pathway and space separation from electromagnetic energy sources, recommends the following:
Unshielded power lines or electrical equipment in proximity to open or nonmetal pathways. If power is less than 480 volts, 5 inches of separation is required.
Unshielded power lines or electrical equipment in proximity to a grounded metal conduit pathway. If less than 480V, 2.5 inches of separation is required.
Many installers may not know the standard but understand only that some separation is required. However, installers should know the exact criteria and follow these standards. I would like to suggest that when you publish an article, you list the standard covering the topic.
Tim Murphy, RCDD
Apex Communications Inc.
Sunnyvale, CA
Thanks to Tim Murphy for this suggestion. If appropriate, we will try to do this in future articles.--Ed.