Question 6Refrigeration & AC - 1st Asst/Chief

The correct answer is A) closed until the motor is connected across the line at full voltage and current drawn is below full load current. The suction gas variable inlet guide vanes are designed to be closed during the motor start-up phase of a hermetically sealed centrifugal refrigeration system. This helps to prevent motor overload by restricting the flow of suction gas to the compressor, which in turn limits the current drawn by the motor until it is connected to the full line voltage. Once the motor is running at full voltage and the current drawn is below the full load current, the inlet guide vanes can then be opened to allow normal system operation. The other options are incorrect because they either have the guide vanes in the wrong position during start-up (B and D) or suggest allowing the motor to draw full load current during start-up, which could lead to an overload condition (C).