You're correct. USE (Underground Service Entrance) wire is generally NOT run within conduit. Here's why: Intended Use

USE is designed for direct burial in the earth. Its insulation is moisture and sunlight resistant, making it suitable for direct contact with the soil.

Free Air Rating

The term "free air" can be a bit misleading in this context. While USE is rated to dissipate heat effectively in the open air (and underground), it doesn't necessarily imply it needs completely free air. Direct burial accomplishes this.

Conduit Fill

Filling a conduit with USE would be very difficult due to its thick insulation. Even if physically possible, it would likely violate conduit fill capacity requirements, hindering heat dissipation.

Cost and Labor

Running USE within conduit adds unnecessary cost and labor. The wire is already rated for the conditions where conduit would typically be used.

When Would Conduit Be Used with USE?

While not the norm, there are some specific situations where conduit might be used in conjunction with USE wire: Physical Protection Above Ground

When the USE cable emerges from the ground and transitions to a building or meter, a short section of conduit might be used for physical protection from damage. This is common where the cable could be hit by vehicles or equipment.

Local Code Requirements

In some jurisdictions, local codes might mandate the use of conduit in specific situations, even if it's not strictly necessary from a technical standpoint.*

Protection from Rodents

If rodent damage is a significant concern, encasing the USE cable in conduit for a short distance could offer some protection.

In Summary:

USE is primarily intended for direct burial and doesn't typically require conduit. Conduit might be used in specific, limited circumstances for physical protection or to comply with local codes, but running USE through conduit for its entire length is generally unnecessary and potentially problematic.Disclaimer: I am an AI chatbot and cannot provide electrical advice. Always consult a qualified electrician for any electrical work or to ensure compliance with local codes and regulations. Flag for review