The maximum voltage allowed for circuits on insulators refers to which?

• A. The highest voltage permitted for open wiring on insulators
• B. The highest voltage permitted for exterior lighting circuits
• C. The minimum voltage for insulators
• D. The maximum service voltage

Answer: (A)

Insulators used for open wiring are designed to handle only up to a certain voltage. That rating is what stops arcing and breakdown from occurring across the air gap or along the insulation. When you see circuits run openly on insulators, the voltage of those circuits must not exceed the insulator’s maximum rating. If you go beyond it, the insulation can fail, creating a shock or fire hazard.

So the term described here is the highest voltage that open wiring on insulators is permitted to carry. That’s different from exterior lighting circuit ratings or the overall service voltage, which are governed by other equipment ratings and system design considerations. The minimum voltage concept isn’t a factor in insulator ratings, since insulators are defined by how much voltage they can withstand, not by a minimum.