Article 110 Requirements for Electrical Installations

I. General

110.1	Scope
110.2	Approval

Only approved equipment and conductors are acceptable.

110.3

Examination, Identification, Installation, and Use of Equipment

The Code lists considerations for the examination of equipment such as mechanical strength, electrical insulation, etc.

110.4	Voltages
110.5	Conductors

Copper is to be used unless otherwise specified. Sizes given are for copper unless otherwise specified.

110.6	Conductor SizesExpressed in American Wire Gage (AWG) or in Circular Mils
110.7	Insulation Integrity
110.8	Wiring Methods
110.9	Interrupting Rating
110.10	Circuit Impedance and Other Characteristics

The entire electrical circuit, including all devices and wire, must be chosen and coordinated so that a fault will be cleared before extensive damage takes place.

110.11	Deteriorating Agents
110.12	Mechanical Execution of Work
110.13	Mounting and Cooling of Equipment
110.14	Electrical Connections
110.15	High-Leg Marking
110.16	Flash Protection
110.18	Arcing Parts
110.19	Light and Power from Railway Conductors
110.21	Marking
110.22	Identification of Disconnecting Means
110.23	Current Transformers

 

II. 600 Volts, Nominal, or Less

110.26

Spaces about Electrical Equipment

(A) Clearances for three conditions are noted. Condition 1 consists of live exposed parts on one side and no live or grounded parts on the other side of the working space or guarded live parts (wood or other insulating material used) on both sides of the working space. Condition 2 consists of exposed live parts on one side and grounded parts on the other side. Condition 3 consists of exposed live parts on both sides. For voltages to ground between 0 and 150 V, a minimum clear distance of 900 mm (3 ft.) is required in all cases. For voltages to ground between 151 and 600 V, Condition 1 requires 900 mm (3 ft.) clearance. Condition 2 requires 1.1 m (3½ ft.), and Condition 3 requires 1.2 m (4 ft.). No working space is required behind assemblies where no renewable parts are on the back and all wiring is accessible from the front (such as panelboards). A minimum of 762 mm (30 in.) in width is required in front of electrical equipment as well as room for a 90° opening of doors. There are requirements in the Code when the voltage is not greater than 30 volts rms, 42 volts peak, or 60 volts dc. There are also requirements in existing buildings where equipment is being replaced.

(E) Headroom of 2 m (6½ ft.) is required above service equipment, motor control centers, panelboards, or switchboards, with the exception of dwelling units not in excess of 200 A. If the equipment exceeds 2 m (6½ ft.), headroom shall be at least the height of the equipment.

110.27

Guarding Live Parts

 

III. Over 600 Volts, Nominal

110.30	General
110.31	Enclosure for Electrical Installations
110.32	Work Space about Equipment
110.33	Entrance and Access to Work Space
110.34	Work Space and Guarding
110.36	Circuit Conductors
110.40	Temperature Limitations at Terminations

 

IV. Tunnel Installations Over 600 Volts, Nominal

110.51	General
110.52	Overcurrent Protection
110.53	Conductors
110.54	Bonding and Equipment Grounding Conductors
110.55	Transformers, Switches, and Electrical Equipment
110.56	Energized Parts
110.57	Ventilation System Controls
110.58	Disconnecting Means
110.59	Enclosures

 

V. Manholes and Other Electric Enclosures Intended for Personnel, All Voltages

110.70	General
110.71	Strength
110.72	Cabling Work Space
110.73	Equipment Work Space
110.74	Bending Space for Conductors
110.75	Access to Manholes
110.76	Access to Vaults and Tunnels
110.77	Ventilation
110.78	Guarding
110.79	Fixed Ladders