By Eileen Harvey
Tray cables can be buried underground, but only if they are specifically designed and rated for direct burial. Not all tray cables are suitable for underground installation, and using the wrong cable type or installation practice can cause premature cable failure, safety hazards or code violations. This article explains when and how tray cables can be buried underground, the necessary ratings and standards, installation best practices and essential compliance considerations.
What Are Tray Cables?
Tray cables are multi-conductor electric cables designed for use in cable trays or raceways or supported by messenger wires. They are commonly used in industrial and commercial settings to carry power, control signals and instrumentation data. They are constructed with durable insulation and jacketing materials to withstand mechanical stress, abrasion, sunlight, moisture, chemicals and temperature extremes.
Because tray cables are listed and tested for harsh environments, they often lower installation costs by eliminating the need for conduit in many cases, especially if the cable has additional protective ratings.
What Does Direct Burial Mean?
Direct burial tray cables are made to withstand exposure to soil and underground conditions without needing additional mechanical protection like conduit or ducting. They can be installed directly in trenches and withstand moisture and water exposure, soil chemicals and abrasives, physical stresses such as crushing or impact from rocks and earth pressure, and temperature variations underground.
To qualify a cable as direct burial, manufacturers apply specialized insulation and jacketing materialsꟷtypically abrasion-resistant PVC, polyethylene or cross-linked polyethylene (XLPE). The cable assembly undergoes rigorous testing to meet industry safety and performance standards.
Identifying Direct Burial Tray Cables
Direct burial tray cables are labeled with markings such as DIRECT BURIAL, DIR BUR and a UL listing specifying direct burial suitability. These markings assure installers and inspectors that the cable complies with National Electrical Code (NEC) and Underwriters Laboratories (UL) requirements for underground installation.
Installation Requirements for Underground Tray Cable Burial
Direct burial tray cables require careful installation to ensure longevity and safety:
Trench Preparation: The cable trench should be free of sharp rocks or debris. Bedding the cable in sand or fine soil provides additional protection from mechanical damage.
Protective Measures: In many installations, warning tapes are buried above the cable path to alert future excavators. Concrete or stone slabs may be used for additional crushing protection in high-traffic areas.
Minimum Burial Depth: Local electrical codes and the NEC specify minimum burial depths, typically from 24 to 42 inches depending on voltage, soil conditions and expected surface loads.
Cable Support and Routing: Cable trays or raceways transition to underground runs must be well supported and routed to prevent damage.
Environmental Considerations: The cable jacket and insulation must withstand moisture, soil contaminants, temperature changes and possibly chemical exposure.
Benefits of Using Direct Burial Tray Cable
Choosing a TCDB cable for underground installation offers several advantages:
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No Conduit Needed in many cases, which can reduce material and labor costs.
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Durability — resists mechanical damage and environmental wear.
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Weather Resistance — performs in wet, dry or direct sunlight conditions.
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Flexibility — approved for both underground and exposed runs.
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Cost Savings — simplifies routing between outdoor and indoor equipment without transitions.
When to Use Conduit or Duct for Underground Cable Protection
If a tray cable is not rated for direct burial, it must be installed in conduit or ducting to provide mechanical and moisture protection before being buried underground. This is mandatory to comply with electrical codes and prevent cable damage.
Common conduit types for underground installations include PVC conduit, rigid metal conduit (RMC) and high-density polyethylene (HDPE) conduit.
Using conduit increases installation cost and complexity but is essential when direct burial cables are unavailable or not suitable.
6 Best Practices for Underground Tray Cable Installation
Even with a direct burial rating, proper installation is key to longterm reliability. Follow these guidelines:
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Prepare the Trench: Excavate to the required depth, ensuring the bottom of the trench is free from sharp stones, roots or debris that could puncture the cable jacket.
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Use Protective Bedding: Lay a 4- to 6-inch bed of sand or screened soil to cushion the cable and protect it from damage.
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Install the Cable: Gently place the tray cable into the trench. Avoid twisting or forcing bends tighter than the manufacturer’s minimum bend radius.
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Backfill Carefully: Cover the cable with another layer of protective bedding before backfilling with native soil.
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Add Warning Tape: Place brightly colored burial warning tape about 12 inches above the cable to alert future excavators of its presence.
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Avoid Waterlogged Areas: While direct burial tray cables are moistureresistant, avoid installing them in areas with persistent standing water whenever possible.
Underground electrical work demands a careful balance of safety, performance, and compliance. Using a direct burial-rated cable like those offered by TKD Kabel ensures safe, code-compliant and long-lasting underground electrical installations.
By following correct installation practices and choosing the right cable for the application, you can reduce risks, save costs and build a more reliable electrical system from the ground up.
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