CFR > Title 30 - Mineral Resources > CHAPTER I—MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR > SUBCHAPTER B—TESTING, EVALUATION, AND APPROVAL OF MINING PRODUCTS (parts 5 to 36) > PART 18—ELECTRIC MOTOR-DRIVEN MINE EQUIPMENT AND ACCESSORIES > SUBPART B—Construction and Design Requirements (§18.20 to §18.54) > 18.24—Electrical clearances.

18.24—Electrical clearances.

Minimum clearances between uninsulated electrical conductor surfaces, or between uninsulated conductor surfaces and grounded metal surfaces, within the enclosure shall be as follows:
Minimum Clearances Between Uninsulated Surfaces
Phase-to-Phase Voltage (rms) Clearances (inches)
Phase-to-Phase Phase-to-Ground or Control Circuit
0 to 250 0.25 0.25
251 to 600 0.28 0.25
601 to 1000 0.61 0.25
1001 to 2400 1.4 0.6
2401 to 4160 3.0 1.4

Code of Federal Regulations

[57 FR 61209, Dec. 23, 1992]