Section 25/Clearances Between Conductors
NESC Rule 25 establishes minimum clearances between supply conductors and between supply and communication conductors on the same or adjacent structures.
Conductors on the same supporting structure must maintain minimum vertical and horizontal separation based on their voltage levels. Supply conductors of different voltages must maintain clearances per Table 235. Communication conductors must be separated from supply conductors by the communication worker safety zone. At crossings between lines on different structures, the higher-voltage line must be positioned above the lower-voltage line with clearances per Rule 233.
Why this section exists
Conductors that swing too close together in wind or ice conditions can contact each other, causing short circuits, equipment damage, and fire. Conductors at different voltages must be separated to prevent flashover. Communication workers must be protected from accidental contact with supply conductors by maintaining a dedicated safety zone on the pole.
What plan reviewers look for
Plan reviewers check pole framing diagrams for conductor spacing at attachment points. They verify that supply and communication conductors are in the correct zones on the pole (supply above communication). They check that conductors of different voltages maintain the required separation at the pole and at mid-span under maximum sag and swing conditions.
Common violations
Related NESC requirements
Rule 23 covers clearances from ground and structures. Rule 24 covers clearances from structures and surfaces. Table 235 provides specific conductor separation values by voltage.