Underground Wires: Do They Need to Be in a Conduit?

The installation of underground wires is a critical aspect of electrical safety and code compliance. Different jurisdictions have varying regulations, but understanding these rules can help ensure your electrical installations are both safe and legally compliant. This article will explore the necessity of running underground wires in a conduit and highlight best practices to follow.

Grounding Electrodes and Conduits in Chicago

In the jurisdiction of Chicago, the grounding electrode conductor is required to be installed in a metallic conduit, which must be bonded at both ends. Equipment grounds that are not the conduit itself must also be installed inside the conduit. This is a standard practice to enhance both the safety and durability of the installation.

Flexible Liquid Tight Conduits

Flexible liquid tight conduits are commonly used in electrical installations due to their flexibility and ease of use. These conduits often come with fittings that have external lugs to accommodate external grounding bonding conductors. This feature is particularly useful in ensuring that all components are effectively bonded and grounded.

In Crawl Spaces and Basements

Wiring in a crawl space or basement is typically treated similarly to wiring in a basement. On one hand, if the wires can be installed in holes bored through joists, no conduit is necessary. On the other hand, if the wires cannot be properly secured in such a manner, using conduits is recommended for protection.

I personally prefer using conduits to avoid running wiring directly in a crawl space, as the crawl space environment is often damp and can cause corrosion. Using conduits helps to prevent such issues and ensures that the wires are protected from moisture and potential damage.

Protection Against Abrasion

When running power wires underground, it is usually advisable to run them in conduit for protection. However, a large bare copper ground wire can be placed at the bottom of the trench before the soft sand is added for the conduit to rest in. Stripping the jacket off 2 AWG wire for the ground wire can provide better grounding properties than using ground rods alone.

It is crucial to ensure that any “exposed” wiring—meaning any wiring not concealed within a wall—is installed in conduit if it is within normal reach. This includes wires running horizontally between floor/ceiling joists, which do not need to be in conduit. However, wires running vertically between the floor and ceiling must either be inside a wall or in conduit to avoid abrasion.

One exception to this rule is the use of non-metallic wire types, such as “NM” (Romex) wiring, which may be used inside conduit. However, this method is not always recommended, and local authorities should be consulted to confirm the regulations in your area.

Direct Burial and Conduits

Although many types of cable are approved for direct burial, using a conduit can provide additional protection. This is especially important in areas prone to seismic activity.

Rarely is direct burial of wires allowed without conduit. In cases where direct burial is possible, special attention must be paid to the soil type and the need for sand bedding. However, for standard installations, it is often recommended to use conduit to protect the wires from damage and to comply with electrical codes.

For coax and CAT 5/6/7 Ethernet Wiring, direct burial is also possible, but it is recommended to keep these networks separate from electrical wires by at least 8 to 12 inches (30 cm) and if needed, up to 18 inches (46 cm) to avoid interference and improve data transfer rates. In some cases, depth might reach as much as 48 inches (1.22 m).

Conclusion

Proper installation and protection of underground wires are critical for electrical safety and code compliance. Whether you are working in a crawl space, basement, or outdoors, using conduits can significantly enhance the security and longevity of your electrical installations. Always verify the local electrical codes to ensure that your work complies with all regulations in your area.