Going Underground: Wire Management in Direct Burial Projects
Chuck Ross
Not all wiring is created equal – after all, some of it has to be buried underground. While this cable might not see the varied weather exposure of unburied, outdoor lines, it faces its own unique challenges. Direct-burial cable doesn’t get the protection conduit offers against pressure and moisture infiltration, so it has to be engineered to withstand those conditions on its own. And the connectors electrical contractors use during installation also require some added design features.
Testing methods ensure direct-burial underground cable is up to its job – these include evaluation for crush resistance and water absorption to learn if products can stand up to soil acidity along with wet, dry and moist conditions. Manufacturers incorporate a number of features to support this performance. These can include:
Direct burial cables with copper conductors generally fall into one of two categories. Underground service entrance (USE) varieties are black and often used to bring power to residences from a utility transformer. Underground feeder cables are gray and sold in rolls that look like non-metallic sheathed cables. These can be used both indoors and outside, as they feature a solid plastic sheath for protection.
Connectors used in direct burial applications require similar care to maintain protection and code compliance. These can include options like heat-shrink splice kits that seal the area around a connection, as well as mechanical connectors that don’t require taping and are prefilled with an oxide inhibiting compound to protect against corrosion.
Testing methods ensure direct-burial underground cable is up to its job – these include evaluation for crush resistance and water absorption to learn if products can stand up to soil acidity along with wet, dry and moist conditions. Manufacturers incorporate a number of features to support this performance. These can include:
- Water-blocking gel injected into the cable to fill all gaps and crevices.
- Water-blocking tape wrapped in the internal wiring for additional moisture/water protection.
- Mylar tape wrapped around internal wires, with an additional aluminum tape wrapped around the mylar for added protection and cable shielding.
Direct burial cables with copper conductors generally fall into one of two categories. Underground service entrance (USE) varieties are black and often used to bring power to residences from a utility transformer. Underground feeder cables are gray and sold in rolls that look like non-metallic sheathed cables. These can be used both indoors and outside, as they feature a solid plastic sheath for protection.
Connectors used in direct burial applications require similar care to maintain protection and code compliance. These can include options like heat-shrink splice kits that seal the area around a connection, as well as mechanical connectors that don’t require taping and are prefilled with an oxide inhibiting compound to protect against corrosion.
Photo courtesy of ILSCO
