Where should you check voltage input to a compressor?

Checking the voltage input to a compressor at the load side of the contactor is the appropriate choice because it allows you to measure the actual voltage being supplied to the compressor when the system is operational. The contactor acts as a switch that controls power to the compressor. By measuring at the load side, you can verify that the compressor is receiving the correct voltage under working conditions, which is crucial for diagnosing any issues related to the compressor’s performance.

Measuring at the disconnect switch, while important for safety and ensuring power is cut off when servicing, does not provide the context of how much voltage is reaching the compressor when the system is running. Similarly, checking at the capacitor terminals or at the air handler junction box would not yield an accurate representation of the voltage directly influencing the compressor operation. These locations may include additional components that can affect or obscure the readings you would take. Thus, measuring voltage at the load side of the contactor is essential for accurate troubleshooting in HVAC systems.