Incoming Power Lines
- Determine the type and number of conductors with the incoming service.
- Evaluate the height of the incoming service cables above the ground or grade level.
- Observe potential obstructions, such as tree limbs, in the area.
- Determine if the mast or service head is correctly oriented and properly secured to the structure.
- Count the number of service conductors attached to the weather head. The number of service/entrance conductors determines the voltage of the service.
- A 120-volt, single-phase system consists of two conductors; an ungrounded phase (hot) conductor, and a grounded (neutral) conductor. The 120-volt single-phase service can only supply power to single phase loads (i.e., 120 volt circuits only).
- A 120/240-volt single-phase system consists of three conductors; two ungrounded phase (hot) conductors, and one grounded (neutral) phase conductor. This system will supply both 120-volt loads and 240 single-phase loads to a dwelling.
- The size and material of the individual conductors determine the ampacity of the service conductors (ie., copper or aluminum). More than 95% of modern day services are stranded aluminum conductors.
- Underground or lateral service extends from the transformer to the meter base of the dwelling. An underground service must be at least a #8 copper or #6 aluminum SEC. The cables must be buried a minimum of 24 inches from finished grade to the top of the cable. (Check local requirements for burial depths).
Determine the Ampacity of the Service
Ampacity is determined by the smallest of three components:
- Type and size of the service entrance cable
- Rating of the panel; and
- Size of the main disconnect.
Back To Top
Ensure Overhead Cables are Properly Secured to the Structure
Is the overhead drip loop properly formed? Are wall and/or roof penetrations properly sealed against water and air intrusion?
Locate the main overcurrent protection (panel box). Examine the service cable to determine the service ampacity capability. (Note: The panel box must be located within 5 feet from the point that the SEC enters the dwelling.)