A Class 3 circuit must use a listed Class 3 limited or nonlimited power source because higher-voltage insulation is specified to provide more protection from electric shock.

A Class 3 circuit must use a listed Class 3 limited or nonlimited power source because higher-voltage insulation is specified to provide more protection from electric shock.

• A. it reduces current draw
• B. it provides more protection from electric shock
• C. it is cheaper
• D. it eliminates the need for conduit

Answer: (B)

Class 3 circuits are designed to limit the energy that can be delivered to any person who might contact the conductors, keeping voltage and current within safe, low levels. Because of this safety goal, the power source feeding a Class 3 circuit must be a listed Class 3 source (whether limited or nonlimited) to guarantee those energy limits are met. When the source is restricted, the potential for electric shock is significantly reduced, since even direct contact cannot push enough energy into the body to cause serious harm. The emphasis here is on the energy limit of the source rather than on insulation alone—the insulation may be high, but the core protection comes from the controlled energy delivery. The other options don’t address that safety mechanism: reducing current draw, cost, or conduit needs don’t ensure the same level of shock protection provided by a Class 3 energy-limited source.

Class 3 circuits are designed to limit the energy that can be delivered to any person who might contact the conductors, keeping voltage and current within safe, low levels. Because of this safety goal, the power source feeding a Class 3 circuit must be a listed Class 3 source (whether limited or nonlimited) to guarantee those energy limits are met. When the source is restricted, the potential for electric shock is significantly reduced, since even direct contact cannot push enough energy into the body to cause serious harm. The emphasis here is on the energy limit of the source rather than on insulation alone—the insulation may be high, but the core protection comes from the controlled energy delivery. The other options don’t address that safety mechanism: reducing current draw, cost, or conduit needs don’t ensure the same level of shock protection provided by a Class 3 energy-limited source.