NEC Service Entrance Requirements: Complete Installation Guide
Service entrance work requires coordination with the utility and strict code compliance. Here's everything you need to know about NEC Article 230 requirements.
In This Guide
Types of Electrical Services
Understanding service terminology is essential:
Service Drop
Overhead conductors from the utility pole to the point of attachment on the building. Owned and maintained by utility up to the weatherhead.
Service Lateral
Underground conductors from the utility to the meter base. May be utility-owned or customer-owned depending on jurisdiction.
Service Entrance Conductors
Conductors from the point of connection with the utility to the service disconnecting means. Always customer-owned.
Service Equipment
The main disconnect and associated equipment - typically the main breaker panel or disconnect switch.
Service Drop Clearances (230.24)
Overhead service conductors must maintain minimum clearances to protect people and property:
Vertical Clearances from Ground
| Location | Clearance |
|---|---|
| Above finished grade (pedestrian only) | 10 feet |
| Above residential driveways | 12 feet |
| Above commercial/public roads | 18 feet |
| Above roofs (not readily accessible) | 3 feet* |
*Roof clearance increases to 8 feet if roof slope is less than 4:12 and area is readily accessible.
Clearances from Building Openings
Per 230.9, service conductors must maintain 3 feet clearance from windows, doors, porches, balconies, fire escapes, and similar locations. Exception: Conductors above the top of a window don't need the 3-foot clearance.
Point of Attachment (230.26)
The point of attachment for service drops must be:
- Not less than 10 feet above finished grade
- Located to maintain required clearances
- At a structurally suitable point on the building
Service Mast Requirements (230.28)
When a service mast is used:
- Must be adequate strength to support conductors
- Minimum 2" rigid metal conduit (RMC) or 2" intermediate metal conduit (IMC)
- May require guy wires for additional support
- Service head (weatherhead) must be above point of attachment
Drip Loop Required
Service conductors must form a drip loop below the weatherhead to prevent water from entering the service mast. Individual conductors must extend at least 12 inches outside the weatherhead.
Service Entrance Conductors
Minimum Size (230.42)
Service entrance conductors must have ampacity sufficient for the calculated load but not less than:
- 100 amperes for single dwelling units
- 60 amperes for other than single dwelling units (with limitations)
Common Service Sizes
| Service Size | Copper SE Cable | Aluminum SE Cable |
|---|---|---|
| 100A | 4 AWG | 2 AWG |
| 125A | 2 AWG | 1/0 AWG |
| 150A | 1 AWG | 2/0 AWG |
| 200A | 2/0 AWG | 4/0 AWG |
Note: These are typical values using 75°C termination ratings. Always verify with NEC 310.16 and applicable termination ratings.
Disconnecting Means Requirements (230.70-230.82)
Location Requirements
The service disconnecting means must be:
- Installed at a readily accessible location - either outside or inside nearest the point of entrance
- As close as practicable to where service conductors enter the building
- Marked as suitable for use as service equipment
Maximum Number of Disconnects
Per 230.71, the service disconnecting means can consist of up to six switches or circuit breakers mounted in a single enclosure or group of separate enclosures.
Emergency Disconnect (NEC 2020+)
NEC 230.85 requires an emergency disconnect for one- and two-family dwellings. It must be installed outdoors in a readily accessible location and marked "EMERGENCY DISCONNECT."
Working Space (110.26)
Service equipment requires minimum working clearances:
- Width: 30 inches or width of equipment (whichever is greater)
- Depth: 36 inches minimum
- Height: 78 inches (6.5 feet) minimum
Service Grounding Requirements
Service grounding is critical for safety and proper operation:
Key Requirements
- Grounded conductor (neutral) must be bonded to grounding electrode system at service
- Main bonding jumper connects neutral bus to equipment ground
- Grounding electrode conductor connects to grounding electrode system
- All grounding electrodes present must be bonded together
Grounding Electrode System Checklist
- □Metal underground water pipe (if 10+ feet in earth)
- □Concrete-encased electrode (Ufer ground) - if present
- □Ground ring - if present
- □Ground rod(s) - required if above not present
- □All electrodes bonded together
See our NEC Article 250 Grounding Guide for complete grounding requirements.
200 Amp Residential Service
200A is the standard for modern homes. Here's a typical specification:
200A Service Specifications
- Service Entrance Conductors: 4/0 AWG aluminum or 2/0 AWG copper
- Service Mast: 2" RMC or IMC minimum
- Meter Base: 200A rated, utility approved
- Main Panel: 200A rated, 40+ circuits typical
- GEC to Ground Rod: 6 AWG copper maximum
- GEC to Water Pipe: Per Table 250.66 (4 AWG for 4/0 service)
- Main Bonding Jumper: Per Table 250.66
Calculate Service Loads Instantly
Use Ampora's load calculation tool to properly size residential and commercial services per NEC Article 220.