Note to paragraph (b)(1)(i) of this section: Suitability of equipment for an identified purpose may be evidenced by listing or labeling for that identified purpose.
Note to paragraph (b)(8)(i) of this section: Wooden plugs driven into holes in masonry, concrete, plaster, or similar materials are not considered secure means of fastening electric equipment.
Table S-1-Minimum Depth of Clear Working Space at Electric Equipment, 600 V or Less
Nominal voltage to ground | Minimum clear distance for condition23 | |||||
Condition A | Condition B | Condition C | ||||
m | ft | m | ft | m | ft | |
0-150 | 10.9 | 13.0 | 10.9 | 13.0 | 0.9 | 3.0 |
151-600 | 10.9 | 13.0 | 1.0 | 3.5 | 1.2 | 4.0 |
Notes to Table S-1:
Condition 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 suitable wood or other insulating material. Insulated wire or insulated busbars operating at not over 300 volts are not considered live parts.
Condition B-Exposed live parts on one side and grounded parts on the other side.
Condition C-Exposed live parts on both sides of the work space (not guarded as provided in Condition A) with the operator between.
Note to paragraph (g)(1)(vii)(A) of this section: A dropped, suspended, or similar ceiling that does not add strength to the building structure is not considered a structural ceiling.
"DANGER-HIGH VOLTAGE-KEEP OUT."
Note to paragraph (h)(5)(vi) of this section: Piping and other facilities are not considered foreign if provided for fire protection of the electrical installation.
Table S-2-Minimum Depth of Clear Working Space at Electric Equipment, Over 600 V
Nominal voltage to ground | Minimum clear distance for condition23 | |||||
Condition A | Condition B | Condition C | ||||
m | ft | m | ft | m | ft | |
601-2500 V | 0.9 | 3.0 | 1.2 | 4.0 | 1.5 | 5.0 |
2501-9000 V | 1.2 | 4.0 | 1.5 | 5.0 | 1.8 | 6.0 |
9001 V-25 kV | 1.5 | 5.0 | 1.8 | 6.0 | 2.8 | 9.0 |
Over 25-75 kV1 | 1.8 | 6.0 | 2.5 | 8.0 | 3.0 | 10.0 |
Above 75 kV1 | 2.5 | 8.0 | 3.0 | 10.0 | 3.7 | 12.0 |
Notes to Table S-2:
1 Minimum depth of clear working space in front of electric equipment with a nominal voltage to ground above 25,000 volts may be the same as that for 25,000 volts under Conditions A, B, and C for installations built before April 16, 1981.
2 Conditions A, B, and C are as follows:
Condition 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 suitable wood or other insulating material. Insulated wire or insulated busbars operating at not over 300 volts are not considered live parts.
Condition B-Exposed live parts on one side and grounded parts on the other side. Concrete, brick, and tile walls are considered as grounded surfaces.
Condition C-Exposed live parts on both sides of the work space (not guarded as provided in Condition A) with the operator between.
3 Working space is not required in back of equipment such as dead-front switchboards or control assemblies that has 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 the deenergized parts on the back of enclosed equipment, a minimum working space 762 mm (30 in.) horizontally shall be provided.
Table S-3-Elevation of Unguarded Live Parts Above Working Space
Nominal voltage between phases | Elevation | |
m | ft | |
601-7500 V | 1 2.8 | 1 9.0. |
7501 V-35 kV | 2.8 | 9.0. |
Over 35 kV | 2.8 + 9.5 mm/kV over 35 kV | 9.0 + 0.37 in./kV over 35 kV. |
1 The minimum elevation may be 2.6 m (8.5 ft) for installations built before August 13, 2007. The minimum elevation may be 2.4 m (8.0 ft) for installations built before April 16, 1981, if the nominal voltage between phases is in the range of 601-6600 volts.
29 C.F.R. §1910.303