The NEC (National Electrical Code) doesn't specify a maximum distance that underground conductors can travel before reaching a manhole.However, several factors influence the practical distance between manholes or other access points for underground conductors: Conductor Pulling Limits

Longer distances increase pulling tension during installation. Exceeding the cable's pulling tension rating can damage the insulation and conductor. This is the most common limiting factor. Factors that increase pulling tension include: Cable Weight: Larger conductors are heavier. Conduit Bends: Each bend significantly increases friction. Conduit Size: Too-small conduit increases friction. Conduit Material: Different materials have different friction coefficients.

Voltage Drop

Longer runs of conductors result in greater voltage drop. Voltage drop must be kept within acceptable limits to ensure equipment operates correctly at the load end. This can be mitigated by using larger conductors, but that increases cost and pulling tension.

Accessibility for Maintenance and Repairs

Manholes and handholes provide access for splicing, testing, and repairing cables. Longer distances between access points mean a larger section of cable must be excavated and replaced if there is a fault. This factor often influences the placement of manholes.

Cost

Manholes and handholes are expensive to install. Minimizing their number reduces initial cost. However, this must be balanced against the factors above.*

Local Regulations and Utility Company Standards

Local jurisdictions and utility companies may have their own specific requirements or preferences regarding spacing between manholes.

In summary:

There is no hard and fast "maximum distance" dictated by the NEC alone. Instead, the spacing between manholes is determined by engineering calculations and practical considerations related to pulling tension, voltage drop, accessibility, cost, and applicable local and utility regulations. Engineers will perform cable pulling calculations to determine the maximum pull length based on the conductor size, conduit configuration, and pulling equipment available. Flag for review