Purpose – This procedure describes the input voltage measurements commonly made when installing and/or servicing single-phase and three-phase powered HVAC equipment. Measurement
o f the input voltage is necessary to make sure that the voltage is within the correct range specified by the manufacturer.

This procedure also provides a set of measurements and checks that can be used to troubleshoot electrical problems that commonly occur in HVAC systems. The scope o f the troubleshooting in this procedure is limited to those measurements and/or checks needed to isolate an electrical fault to a functional circuit. Service Procedure SP-8 provides instructions for isolating the fault to a defective component.

Keep in mind that some problems that appear to be electrical may actually be the result of refrigerant-side or air-side problems that cause electrical devices to trip. For example, excessive refrigerant charge can cause the high pressure switch to trip and open the compressor contactor circuit, shutting down the compressor.

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