Oklahoma Electrical Practice Exam

In a class I, Zone II atmosphere, what is the approved binding technique for a 60HP motor?

1. Bonding with a strap

2. Motor to ground

3. Using a bonding wire

4. Grounding to the building structure

The correct answer is: Motor to ground

In a Class I, Zone II atmosphere, the primary concern is to ensure safety in environments where flammable gases or vapors may be present. For a 60HP motor operating in such an environment, proper bonding is essential to prevent the buildup of static electricity, which could lead to an ignition source. Bonding a motor to ground establishes a low-resistance path for fault currents. This is crucial for ensuring that any fault condition, such as a short circuit, is safely dissipated to ground, preventing potential hazards that could arise in the presence of flammable materials. The bonding technique must ensure that the electrical system is adequately connected to a grounding system that is effective in mitigating risks within such hazardous locations. Thus, bonding the motor directly to ground ensures that any stray voltage or electrical imbalances are safely directed away from the motor and any surrounding equipment, effectively minimizing the risk of ignition in the potentially explosive atmosphere present in Class I, Zone II settings.