Heating, Ventilation, and Air Conditioning (HVAC ) Electrical Practice Test

What does it indicate when a run winding shows 1,000 ohms to the motor frame during testing?

1. A short circuit

2. A grounded condition

3. Normal operation

4. An open circuit

The correct answer is: A grounded condition

When a run winding shows 1,000 ohms to the motor frame during testing, this measurement indicates a grounded condition. In an electric motor, the windings should be electrically isolated from the motor frame. If the resistance measurement between the run winding and the motor frame shows a low resistance (like a short circuit), this suggests that the winding has lost its insulation, and current can leak to the motor frame, creating a risk of electrical shock or circuit damage. In this context, a reading like 1,000 ohms suggests a compromised insulation barrier rather than a short circuit or an open circuit. A short circuit would typically be indicated by a very low resistance (close to zero ohms), while an open circuit would show an infinite resistance, indicating no continuity at all. Normal operation would reflect a significantly higher resistive value, often in the megaohm range, indicating that the winding is intact and properly isolated.