How do you determine which hot line is the wild leg in a 250-volt grounded delta power supply?

In a 250-volt grounded delta power supply, determining the wild leg, also known as the "high leg" or "wild leg," involves understanding the configuration of the electrical supply and how the voltages are distributed across the various legs in a delta system with a grounded neutral.

Identifying the leg that does not measure 120 volts to neutral or ground is the correct approach. In a grounded delta system, one leg typically provides 120 volts to neutral, while the wild leg offers a higher voltage to neutral, usually around 208 volts. By measuring the voltage to ground or neutral, you can easily identify the leg that does not conform to the expected 120-volt measurement. This leg is essential as it signifies a different intended use in the system, often utilized for specific applications, such as running three-phase motors or certain auxiliary devices.

The other methods mentioned, such as checking temperature, observing wire colors, or measuring amperage, may not provide reliable indicators of which leg is the wild leg. While temperature could give some insight into electrical load, it is not a definitive method. Wire color can vary according to local codes and practices, which makes it unreliable without further verification. Measuring amperage does not distinguish between the wild leg and the