Your questions answered: How to specify cable cleats
Understand how IEC compliance can mitigate short-circuit disasters and future-proof electrical infrastructure
A KPMG International survey recently found that 78% of surveyed engineering and construction companies believe building project risks are increasing. Clients are challenging engineers to complete projects at an unprecedented pace to realize the return on investment, and the need for infrastructure development in remote and complex environments is increasing. A study by the G20-backed Global Infrastructure Hub and Oxford Economics estimates that $3.7 trillion will be invested in infrastructure every year to meet global demand. It’s no wonder engineering and construction firms are constantly pushing the competitive edge.
To maintain an advantage, it’s paramount to stay at the forefront of safety compliance and best practices. A fundamental move: Specify cable cleats because they assist with electrical system protection. To ensure long-term integrity of electrical infrastructure, follow cable cleat installation standards according to the International Electrotechnical Commission 61914:2015, the most robust standards established globally.
Questions not answered during the live event “How to specify cable cleats” on Aug. 22, 2019, are answered here.
Q: Do you have any cleats that work with 3-phase conductors and a neutral conductor?
Panduit: Yes, our strap cleats can be used to bundle the trefoil 3-phase conductors and the neutral, total of 4 conductors. The same short circuit calculations would apply as if it was a standard trefoil.
Q: Do cable bus manufacturers follow a similar process to mitigate the possibility of cable damage within the cable bus?
Panduit: When we have this situation, the cables are cleated but not attached to the bus duct.
Q: Are cable cleats are applicable for dwelling complexes? Small or large?
Panduit: Cable cleats are applicable anywhere power is distributed with conductors routed in cable tray. Using cleats ensures that the occupants are protected from the impact of the electromechanical forces during a short circuit event. Additionally, anywhere local, regional or country codes require the containment of cable during a short circuit fault, cable cleats designed and tested to IEC 61914:2015 support compliance with those standards.
Q: There are many different cable support systems in the market. Do you offer different mounting options for your cleats?
Panduit: Yes, absolutely! Panduit currently has approximately 10 different attachment brackets for our cleats that support approximately 70% of the cable tray market. Additionally, we are constantly adding custom brackets to support customer requirements for their tray. Custom brackets are always available upon request.
Q: Can you please summarize the pros and cons of a power distribution strategy using cable tray (with cleats), compared with routing cables in conduit, which seems to be more prevalent in North American markets?
Panduit: Conduit is expensive and long runs are an issue. Large cables are difficult to pull into a conduit and they require pull boxes at regular intervals. Cables in a tray are much easier to install and cheaper. I have been on sites with runs longer than 2.5 kilometers and that would be a lot of conduit. Most of the cable we will be cleating is above 150mm sq going through to 1500mm sq, normally in trefoil, which due to size and installation requirements is not suitable for a conduit installation.
Q: How do rigidity of cleats installation accommodate for temperature change?
Panduit: There are a handful of considerations at play here. First, material must also be taken into consideration. Cable Trays are made from aluminum, galvanized steel, stainless steel or fiberglass, conductors of aluminum or copper and construction of armored or unarmored material such as aluminum or steel. All these materials have very specific thermal expansion coefficients based on their properties.
The cable tray that the cleats are installed to typically has thermal expansion joints between sections. If more relief is required, Panduit clip brackets, which are used to attach the aluminum and stainless steel trefoil cleats to the rung, do accommodate for some thermal expansion relief.
Additionally, when pulling and setting the cables into the cleats it’s a best practice to build in some “side-to-side” or “S-shaped” slack between cleats to permit expansion and contraction. Doing this at the expansion joints of the tray sections is particularly beneficial. Another technique to compensate for thermal expansion is to install the cleats on the cables, but leave sections unsecured to the tray.
The Cigre Technical Brochure TB669 offers excellent guidance on this topic and your cable cleat manufacturer, like Panduit, should have an engineering support team that can provide guidance on thermal expansion compensation during installation.
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