Question

Resistors and reactors, for use over 600 volts, shall not be installed in close enough proximity to combustible materials to constitute a fire hazard and shall have a clearance of not less than ___ from combustible materials.

Answer 1

Resistors and reactors, for use over 600 volts, shall not be installed in close enough proximity to combustible materials to constitute a fire hazard and shall have a clearance of not less than 300 mm from combustible materials.

Explanation:

• The hazards associated with high power industrial resistors are primarily due to their open construction, which is necessary for cooling.
• The exposed conductors which make up the resistors can be not only a shock hazard but also a thermal burn hazard.
• When a resistor fails, it either goes open or the resistance increases. When the resistance increases, it can burn the board, or burn itself up.
• Avoid touching non-flammable resistors in operation; the surface temperature ranges from approximately 350 °C to 400°C when utilized at the full rated value. Maintaining a surface temperature of 200°C or less will extend resistors service life.
• Do not apply power to a circuit while measuring resistance. When you are finished using an ohmmeter, switch it to the OFF position if one is provided and remove the leads from the meter.
• Always adjust the ohmmeter for 0 (or in shunt ohmmeter) after you change ranges before making the resistance measurement.