What condition is indicated by the following measurements: Common to run 4 ohms, Common to start 6.2 ohms, Run to start 10.2 ohms, Common to ground 20.4 ohms?

The condition indicated by the measurements suggests a grounded condition. In this scenario, the resistance values show a discrepancy that often points to an issue between the windings and the ground.

When assessing these resistance measurements, the common to ground value of 20.4 ohms is particularly significant. A relatively low resistance reading from a winding (the common) to ground can imply that there is unintended connectivity with the ground, which can result from insulation failure or a fault within the motor.

Typically, in a well-functioning system, one would expect much higher resistance values to ground, indicating good insulation and no electrical connection that would suggest a ground fault. Conversely, readings above a certain threshold from common to ground are indicative of healthy operational conditions. Given that this case shows a lower resistance, it strongly suggests a grounded condition rather than an open circuit, short circuit, or no condition at all, all of which would display different electrical characteristics in terms of resistance. This interpretation highlights the significance of the readings in diagnosing electrical issues within HVAC systems.