- Part Number:1926
- Part Number Title:Safety and Health Regulations for Construction
- Subpart:1926 Subpart K
- Subpart Title:Electrical
- Standard Number:
- Title:General requirements.
- GPO Source:
Working clearances. Except as required or permitted elsewhere in this subpart, the dimension of the working space in the direction of access to live parts operating at 600 volts or less and likely to require examination, adjustment, servicing, or maintenance while alive shall not be less than indicated in Table K-1. In addition to the dimensions shown in Table K-1, workspace shall not be less than 30 inches (762 mm) wide in front of the electric equipment. Distances shall be measured from the live parts if they are exposed, or from the enclosure front or opening if the live parts are enclosed. Walls constructed of concrete, brick, or tile are considered to be grounded. Working space is not required in back of assemblies such as dead-front switchboards or motor control centers where there are no renewable or adjustable parts such as fuses or switches on the back and where all connections are accessible from locations other than the back.
TABLE K-1 - Working Clearances ___________________________________________________________________ | | Minimum clear distance for Nominal voltage to ground | conditions(1) |__________________________________ | | | | (a) | (b) | (c) ________________________________|__________|__________|____________ | | | | Feet(2) | Feet(2) | Feet(2) 0-150 ..........................| 3 | 3 | 3 151-600 ........................| 3 | 3 1/2 | 4 ________________________________|__________|__________|____________ Footnote(1) Conditions (a), (b), and (c) are as follows: [a] Exposed live parts on one side and no live or grounded parts on the other side of the working space, or exposed live parts on both sides effectively guarded by insulating material. Insulated wire or insulated busbars operating at not over 300 volts are not considered live parts. [b] Exposed live parts on one side and grounded parts on the other side. [c] Exposed live parts on both sides of the workplace [not guarded as provided in Condition (a)] with the operator between. Footnote(2) Note: For International System of Units (SI): one foot=0.3048m.
Installations accessible to unqualified persons. Electrical installations that are open to unqualified persons shall be made with metal-enclosed equipment or shall be enclosed in a vault or in an area, access to which is controlled by a lock. Metal-enclosed switchgear, unit substations, transformers, pull boxes, connection boxes, and other similar associated equipment shall be marked with appropriate caution signs. If equipment is exposed to physical damage from vehicular traffic, guards shall be provided to prevent such damage. Ventilating or similar openings in metal-enclosed equipment shall be designed so that foreign objects inserted through these openings will be deflected from energized parts.
Working space. The minimum clear working space in front of electric equipment such as switchboards, control panels, switches, circuit breakers, motor controllers, relays, and similar equipment shall not be less than specified in Table K-2 unless otherwise specified in this subpart. Distances shall be measured from the live parts if they are exposed, or from the enclosure front or opening if the live parts are enclosed. However, working space is not required in back of equipment such as deadfront switchboards or control assemblies where there are no renewable or adjustable parts (such as fuses or switches) on the back and where all connections are accessible from locations other than the back. Where rear access is required to work on de-energized parts on the back of enclosed equipment, a minimum working space of 30 inches (762 mm) horizontally shall be provided.
TABLE K-2 - Minimum Depth of Clear Working Space in Front of Electric Equipment ________________________________________________________________ | | Conditions(1) Nominal voltage to ground |______________________________ | | | | (a) | (b) | (c) _________________________________|_________|_________|__________ | | | | Feet(2) | Feet(2) | Feet(2) 601 to 2,500 | 3 | 4 | 5 2,501 to 9,000 | 4 | 5 | 6 9,001 to 25,000 | 5 | 6 | 9 25,001 to 75 kV | 6 | 8 | 10 Above 75kV | 8 | 10 | 12 _________________________________|_________|_________|________
Footnote(1) Conditions (a), (b), and (c) are as follows:
Exposed live parts on both sides of the workspace [not guarded as provided in Condition (a)] with the operator between.
Footnote(2) NOTE: For SI units: one foot=0.3048 m.
Elevation of unguarded live parts. Unguarded live parts above working space shall be maintained at elevations not less than specified in Table K-3.
TABLE K-3 - Elevation of Unguarded Energized Parts Above Working Space ___________________________________________________________________ | Nominal voltage between | phases | Minimum Elevation ______________________________|____________________________________ | 601-7,500 ....................| 8 feet 6 inches. 7,501-35,000 .................| 9 feet. Over 35kV ....................| 9 feet+0.37 inches per | kV above 35kV. ______________________________|___________________________________ Footnote(1) NOTE: For SI units: one inch=25.4 mm; one foot=0.3048 m.
[61 FR 5507, Feb. 13, 1996]