A Half-Dozen Mysteries Answered
Now let's take a moment to consider some commonly asked questions - a few of which are lifted from CTI materials - surrounding the use of cable trays.
Can a metal cable tray be classified as a cabling "raceway"?
No. Even though the National Electrical Code (NEC) defines a raceway as an enclosed channel of metal expressly designed for holding wires, this exception is made because a cable tray is an "open" structural system.
Can mechanical utility piping or tubing containing compressed air be installed in a cable tray with cabling?
No, NEC section 300.8 does not permit this; only electrical cabling.
I recently noticed that a cable tray was used for some low-voltage cabling and there was no indication of the tray being grounded. Is this a NEC violation?
Actually, low energy systems may not be required to be grounded for shock and arcing. However, it is a good idea to shield for noise, electromagnetic interference (EMI) and lightning protection. A good free reference for cable tray installations can be found in the National Electrical Manufacturers Association (NEMA) VE-2 document (www.nema.org/stds/ve2.cfm).
Do you need to provide cable ties with cabling in a cable tray?
Yes, you need to tie them down to maintain spacing and separate cable-type groups. You will see some indications of not having to tie down in horizontal cable trays, but in other cable type groups it may be necessary. It is a good practice to keep all cabling secured in the tray and properly separated.
Are cable trays UL-Listed?
Metal cable trays are not required to be listed because they are support systems. However, there are UL-Listed trays and you should be careful to comply with what your AHJ requires. Remember the cautions elsewhere in this article on modifying UL-Listed cable trays.
Can a person walk on an installed cable tray system?
No, walking on cable trays is not permitted.
Bob Dolph has served in various technical management and advisory positions in the security industry for 30+ years. To share tips and installation questions, E-mail Bob at [email protected]. Check out his Tech Shack blog.
Tech Talk Tool Tip
Feeling Software’s Omnipresence 3D video surveillance platform transforms standard two-dimensional CAD facility drawings and converts them into a three-dimensional landscape. Courtesy Feeling Software
This month I want to share a software tool I recently discovered. The company is Feeling Software and it has a new, exciting system called the Omnipresence 3D surveillance platform. The company will take your standard two-dimensional CAD facility drawings and convert them to a three-dimensional landscape.
Wow, 3D! Now you can use this software design and implementation software package to set up CCTV in a 3D environment. With this system security operators can follow suspects not only through a particular floor area, but up and down stairs as well. The system really shines when you are applying CCTV to large areas such as a college campus or municipality. It will even allow guards to track suspicious movement, camera to camera, throughout the facility. This product is definitely worth a serious look if you want to propose something your competition is not.