Article 230 Services



This article describes requirements for service conductors and equipment for control and protection of services. Figure 230.1 describes where in Article 230 different parts of the service are described.

I. General


Number of Services

A building normally can have only one service. If more than one is permitted as a result of the exceptions provided, then a directory of all services must be placed at each service. For the purposes of Section 230.40, Exception 2, underground conductors sized at least 1/0 are considered one service if they are connected at the supply but not at the load. More than one service is permitted as follows:

(A) Special Conditions

(1) Fire pumps if required.

(2) Emergency systems.

(3) Legally required standby systems.

(4) Optional standby systems.

(5) Parallel power production systems.

(6) Systems designed to connect to multiple sources of supply for enhanced reliability.

(B) Special Occupancies

(1) In multiple-occupancy buildings where there is no room for each tenant to have access to the service equipment, with permission, more than one set of service conductors can be tapped from one service drop or service lateral.

(2) If a single building is too large then with special permission, more than one service may be installed.

(C) Capacity Requirements

(1) If the capacity requirements are larger than 2000 amperes at 600 volts or less.

(2) If a single-phase installation were larger than the utility would normally serve through one service.

(3) With special permission.

(D) Different Characteristics

More than one service is permitted if there are different rate schedules, voltages, phases, frequencies or uses.

(E) Identification

If a building is supplied by more than one service, feeder, or set of branch circuits, a permanent directory or plaque has to be installed at the disconnect location.


One Building or Other Structure Not to Be Supplied through Another

Service conductors cannot pass through another building.


Conductors Considered Outside of Building

If conductors have a cover of at least 50 mm (2 in.) of concrete under a building or are installed in a raceway encased in at least 50 mm (2 in.) of concrete or are installed in a vault as per Article 450 Part III, or installed in concrete and under at least 450 mm (18 inches) of earth under a building they are treated as being outside the building.


Other Conductors in Raceway or Cable


Raceway Seal


Clearance from Building Openings

If installed as open conductors or multiconductor cable without an outer jacket, clearance of at least 900 mm (3 ft.) is required from operable windows, doors, porches, fire escapes, stairs, ladders, balconies, and the like. There is an exception for conductors above the top level of a window. Overhead service conductors are not permitted underneath openings through which materials can be moved or obstructing these openings. Vertical clearances under certain conditions are to be maintained in accordance with Section 230.24(B).


Vegetation as Support Not Permitted


II. Overhead ServiceDrop Conductors


Insulation or Covering

Insulation or covering is required on individual conductors.


Size and Rating

Conductors should have the capacity required for the load in accordance with Article 220 and have enough mechanical strength. The minimum size should be 8 AWG copper or 6 AWG aluminum or copper-clad aluminum. Grounded conductors shall be as required in Section 250.24(B). There is an exception.



Service-drop conductors must not be accessible and comply with the following:

(A) 2.5 m (8 ft.) vertical clearance maintained above the roof with 900 mm (3 ft.) from the edge of the roof is generally the clearance required above roofs with a nominal voltage of 600 V except where the service drop is attached to the side of the building. This is reduced to 900 mm (3 ft.) with a voltage of 300 V and a roof slope of 100 mm (4 in.) in 300 mm (12 in.) or more. It is also reduced to 450 mm (18 in.) above the overhanging portion with a nominal voltage of 300 V if only up to 1.8 m (6 ft.) of service drop conductors, 1.2 m (4 ft.) horizontally, pass over the roof and the conductors end on a support or raceway. Where there is traffic above a roof surface use requirements of Section 230.24(B).

(B) The clearances above the ground vary for conductors with a nominal voltage of 600 V. They are:

3.0 m (10 ft.): voltage of 150 V to ground, service entrance to buildings accessible to pedestrians.

3.7 m (12 ft.): over residential property and no truck traffic commercial areas with voltage to ground not in excess of 300.

4.5 m (15 ft.): at areas listed in 3.7 m (12 ft.) classification when the voltage exceeds 300 V to ground.

5.5 m (18 ft.): over public streets. Private property is included if traveled with commercial vehicles.

(C) Refer to Section 230.9 for clearances from building openings.

(D) Refer to Section 680.8 for clearances from swimming pools.


Point of Attachment

A minimum clearance of 3.0 m (10 ft.) is required. Compliance with 230.9 and 230.24 is required.


Means of Attachment


Service Masts as Support


Supports over Buildings


III. Underground ServiceLateral Conductors



Generally, they are insulated with the voltage determining the insulation. There are some exceptions for grounded conductors of bare wire and aluminum or copper-clad aluminum cable assemblies.


Size and Rating

The conductors must be large enough to carry the load in accordance with Article 220. No smaller than 8 AWG for copper and 6 AWG for aluminum or copper-clad aluminum. An exception is made where the service supplies only a single load on a single branch circuit. The grounded conductor must not be sized less than required in Section 250.24(B).


Protection against Damage


Spliced Conductors


IV. Service-Entrance Conductors


Number of Service-Entrance Conductor Sets

Generally, a service drop or lateral can only supply one set of service conductors. However, one set of service conductors can supply each occupancy or a group of occupancies in a multiple- occupancy building. A second exception for separate enclosures is noted. A third exception is noted for single family or a separate structure. There are two additional exceptions.


Insulation of Service-Entrance Conductors

Generally, if the conductors are on or enter a building, they should be insulated. Exceptions are made for grounded conductors of bare copper wire and aluminum, copper-clad aluminum cable assemblies in special cases, copper for direct burial where the copper is all right for the soil, and aluminum or copper-clad aluminum part of an assembly rated for direct burial.


Minimum Size and Rating

(A) General. The ampacity of the conductors is to be either the sum of the noncontinuous load and 125% of the continuous load or the sum of the noncontinuous and continuous loads if the overcurrent devices are rated for operation at 100% of their rating. The loads are calculated in accordance with Article 220. The ratings are determined in accordance with Section 310.15. For busways use the listing or rating of the busway.

(B) Ungrounded Conductors. Use at least the rating of the disconnecting means as specified in Section 230.79(A) through (D).

(C) Grounded Conductors. Size in accordance with Section 250.24(B).


Wiring Methods for 600 Volts, Nominal, or Less

Only the following methods are permitted: Open wiring on insulators; type IGS cable; rigid metal conduit; intermediate metal conduit; EMT; ENT; service entrance cables; wireways; busways; auxiliary gutters; rigid NMC; cablebus; MC cable; mineral-insulated, metal-sheathed cable; flexible metal conduit or liquidtight flexible metal conduit with certain restrictions; or liquidtight flexible nonmetallic conduit.


Cable Trays

To support cables, a cable tray system may be used.


Spliced Conductors


Protection against DamageUnderground


Protection of Open Conductors and Cables against DamageAbove Ground


Mounting Supports


Individual Conductors Entering Buildings or Other Structures


Raceways to Drain


Overhead Service Locations

Connections to the service drop conductors have to be made raintight with a raintight head or with a gooseneck. The heads or goosenecks must be above the point where the conductors are attached to the building and must be securely attached. Drip loops must be constructed to prevent entrance of moisture. There are other requirements.


Service Conductor with the Higher Voltage to Ground


V. Service EquipmentGeneral


Service EquipmentEnclosed or Guarded

Energized parts must be enclosed so that no one can make accidental contact or guarded. If energized parts are not enclosed then they must be guarded as noted in 110.18 and 110.27. If the energized parts are guarded in accordance with 110.27(A)(1), then there has to be a provision for locking or sealing the doors.



Service equipment must be marked for use as service equipment.

VI. Service EquipmentDisconnecting Means



There must be a way to disconnect all conductors in the building from the service-entrance conductors. The disconnect must be readily accessible either outside the building or inside the building nearest the point of entrance of the service conductors. It must have proper markings and be suitable for its use. Service disconnects cannot be installed in bathrooms. If a remote control device is used to actuate the service disconnect then the service disconnect must still be at a readily accessible location. The service disconnecting means must be suitable for the conditions where it is installed. Refer to Articles 500 through 517 for hazardous locations.


Maximum Number of Disconnects

The provision for disconnecting each service (Section 230.2) or the service entrance conductors (Section 230.40, Exception Nos. 1, 3, 4, or 5) can consist of no more than six switches or six circuit breakers or combinations. Single-pole units can be used for multiwire circuits, one pole for each ungrounded conductor. They must be tied together as a multipole disconnect and will then be counted as one disconnect. An exception is made for the control circuit of a ground-fault protection system, power monitoring equipment, transient voltage surge suppression, or power-operable service disconnecting means.


Grouping of Disconnects

All disconnects are to be grouped together. There is an exception for a disconnect used for a water pump for fire protection. If there are additional services as permitted in 230.2 for emergency systems, legally required standby or operational standby systems, or fire pumps, then the disconnecting means must be installed away from the normal service disconnecting means so that the possibility of interrupting the services at the same time is reduced. Where multiple occupancies are present, each occupant must have access to his or her own disconnect. There is an exception to this latter requirement for certain management conditions.


Simultaneous Openings of Poles


Disconnection of Grounded Conductor


Manually or Power Operable




Rating of Disconnect

In general, the service disconnect must be sized to carry the calculated load. There are special cases where a minimum size is required. They are:

15 A: a single branch-circuit load

30 A: up to two, two-wire branch circuits

100 A: three-wire: one-family dwelling

60 A: all other cases


Combined Ratings of Disconnects

If more than one service switch is used, their combined rating must be at least the rating shown in Section 230.79.


Connection to Terminals


Equipment Connected to the Supply Side of Service Disconnect

Among the pieces of equipment allowed to be connected to the supply side of a service switch are: current-limiting devices, meters, instrument transformers, surge protective devices, fire and sprinkler alarms, fire pump equipment, and interconnected electric production sources. Some of these items require separate protection and disconnects. Refer to the NEC® for a complete description and list.

VII. Service EquipmentOvercurrent Protection


Where Required

(A) Every ungrounded conductor must have an overcurrent device. It must normally not be set higher than the rating of the conductors. There are five exceptions to this and they include: motor starting current; fuses and circuit breakers conforming to Section 240.3(B) or (C) and Section 240.6; six fuses or circuit breakers is the limit for consideration as a service overcurrent device; fire pumps under certain conditions; when permitted by Section 310.15(B)(6) for 120/240 volt, three-wire, single-phase dwelling services.

(B) No overcurrent device is to be placed in a grounded conductor.



The service overcurrent device must be part of the service disconnect or be next to it.


Locked Service Overcurrent Devices


Protection of Specific Circuits


Relative Location of Overcurrent Devices and Other Service Equipment

Some of the items allowed ahead of the overcurrent device are: service switch, surge protectors, protective signaling systems, fire pump, meters, and power-operable service equipment controls.


Ground-Fault Protection of Equipment

This is required for all services that are 150 V to ground up to 600 V phase to phase, solidly grounded wye, with service switches 1000 A or more. The grounded conductor must be connected directly to ground. No impedance device is allowed. The rest of this section contains information about the setting of these devices, the use of switches and fuses, and performance testing. An exception is allowed for continuous industrial processes where a nonorderly shutdown would be hazardous and for fire pumps. Refer to 517.17(A) for hospitals or other buildings with critical areas or life support equipment.

VIII. Services Exceeding 600 Volts, Nominal




Service-Entrance Conductors


Isolating Switches


Disconnecting Means


Overcurrent Devices as Disconnecting Means


Protection Requirements


Surge Arresters (Lightning Arresters)


Service EquipmentGeneral Provisions


Metal-Enclosed Switchgear


Services over 35,000 Volts

Article 90 Introduction


Wiring and Protection

Wiring Methods and Materials

Equipment for General Use

Special Occupancies

Special Equipment

Special Conditions


Annex C. Conduit and Tubing Fill Tables for Conductors and Fixture Wires of the Same Size

Annex D. Examples

Annex E. Types of Construction

Pocket Guide to the National Electrical Code 2005
Pocket Guide to the National Electrical Code(R), 2005 Edition (8th Edition)
ISBN: 0131480014
EAN: 2147483647
Year: 2004
Pages: 120 © 2008-2020.
If you may any questions please contact us: