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Cable tray systems are structures designed to support cable runs on flat or sloped roofs. Traditionally, facilities chose to bundle cables and assemble them in a way that provides little protection, or run cables through tubular electrical conduit systems, which hinders cable access, impedes ventilation, and may trap moisture inside the enclosure. Cable trays and cable tray supports provide an organized, easy-to-manage solution for rooftop cable networks that can be adjusted to any height or width, routed around walkways and equipment, and configured for proper ventilation and drainage.
If cable trays are not properly designed and installed, incorrect network cabling can lead to maintenance problems, repair costs and even downtime. The following are five common cable tray mistakes to avoid when setting up or retrofitting a network:
1. When you determine the number of cables to meet today's needs, you should also calculate future demand. Communication and electrical pathways are stable components whose expected life far exceeds that of the wiring systems they contain. As systems will still converge and expand with emerging applications, the number of cables you need will definitely increase. Placing a larger cable tray now and then upgrading your network infrastructure later saves more time and cost.
2. Failure to properly install cable trays can lead to safety hazards, from failure to properly secure cables to complete collapse of the tray. "Install various supports, such as support locations for straight sections and fittings, as well as locations for splice joints. Charts are provided for calculating how often expansion joints are needed, as well as methods for properly setting expansion joint gaps, and locations for fixing clamps and expansion rails.
3. There are many different types of cable trays to choose from, from ladders to ventilated troughs, to wire baskets to solid bottoms. Understanding the types of cables and the installation environment will determine the cable tray you want to choose. For example, single-core cables must be installed in ladders or ventilated troughs. Solid-bottom trays are usually only specified where shielding protection may need to be considered. Low-voltage telecommunications cables, control and signal cables are traditionally placed in wire basket cable trays. The weight capacity and cable volume of the tray must be calculated in order to specify the correct tray standard. Trays requiring larger spans will require larger side rail cross-sectional areas. It is crucial that you fully understand all aspects of the installation in order to know which cable tray can do the simple job.
3. As long as they are properly designed, installed and inspected, aluminum and steel cable tray systems are excellent equipment grounding conductors, and these types of cable trays are allowed to be used as equipment grounding conductors when essentially also marked with available cross-sectional area. If cable trays are to be used as reinforcement, bonding jumpers must be placed on both side rails of each tray joint, unless splice plates meet electrical continuity requirements. If tray connections are classified, no bonding jumpers or continuous grounding components are required. It is important to check the grounding of the cable tray system, including the cables within the tray, before energizing cables within the tray and installing cables. This will help eliminate any hazardous situations that occur due to improper bonding.
4. Overfilling cable trays can cause cable performance to deteriorate, become damaged and become a safety hazard. By considering the size, voltage and number of conductors, the need for installing cables within cable trays is outlined in order to develop the correct cable fill rate based on the cross-sectional area of the tray. Where low-voltage communication cables are used, the 40% or 50% rule is usually adopted. Due to safety concerns associated with higher voltages, it becomes more stringent for cables. Generally, the sum of the diameters of all single-core cables should not exceed the width of the cable tray, so cables should be laid in a single layer.
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