NATE Air Conditioning and Heat Pumps Practice Exam

Hard-start kits are often needed on ____.

1. reciprocating compressors used with TEVs

2. rotary compressors used with fixed metering devices

3. scroll compressors used with TEVs

4. three-phase compressor used with fixed metering devices

The correct answer is: reciprocating compressors used with TEVs

Hard-start kits are often required on reciprocating compressors used with thermostatic expansion valves (TEVs) due to the unique starting characteristics of these systems. Reciprocating compressors have a higher starting torque requirement compared to other types of compressors. When they start, they may experience higher inrush current, which can lead to problems in system operation, including tripping circuit breakers or damaging the compressor. The inclusion of a hard-start kit, which typically consists of a potential relay and a start capacitor, helps provide that necessary boost of energy when the compressor first powers on. This assists in overcoming the initial resistance and allows the compressor to start more reliably under varying conditions, thus ensuring smoother and more efficient operation. Reciprocating compressors are commonly linked to systems using TEVs, as these valves regulate refrigerant flow based on superheat, which adds further complexity to the system’s operation at startup. This dynamic makes the hard-start kit a vital component in ensuring both effective startup and overall reliability of the refrigeration circuit.