System Troubleshooting

Table of Contents

Chapter 1: Preparation for Troubleshooting

Topics: Mechanical refrigeration systems; Keys to effective troubleshooting; Safety in troubleshooting; Tools and equipment; Supplies; Human relations skills

Learning Objectives:

• Give an example of each of the following applications: process refrigeration, commercial refrigeration, process air conditioning, comfort air conditioning.
• Tell what knowledge is essential for an effective troubleshooter to have.
• Tell what safety precautions must be followed when dealing with the mechanical, electrical, chemical, and environmental hazards involved in troubleshooting.
• List the necessary tools, equipment, and supplies needed to perform troubleshooting procedures.
• Explain why human relations skills are important to the refrigeration system troubleshooter.

Chapter 2: Troubleshooting Procedures

Topics: Six steps of troubleshooting; Avoiding a recurrence of the problem

Learning Objectives:

• Name the six basic steps in the troubleshooting procedure.
• Explain why it is important to collect information from the equipment operator when a system is malfunctioning.
• Explain what type of information is contained on a nameplate and in the operations log of a system.
• Explain the structure and use of troubleshooting charts.
• Explain how to set up a preliminary checklist and how to select the most likely components and subsystems for further examination.
• List items to check out after making repairs to a refrigeration system.

Chapter 3: Troubleshooting Electric Controls

Topics: Troubleshooting flowchart; Checking the contactor; Faulty coils; Relays and switches; The power side

Learning Objectives:

• Explain how to use a troubleshooting chart.
• Explain how to isolate a control circuit failure from a motor circuit failure.
• List the causes of abnormally high control circuit resistance.
• Explain the difference between using an ohmmeter and using a voltmeter to check for a closed electric switch.
• Describe how to check contactor coils and motors for shorts and opens.

Chapter 4: Troubleshooting Pneumatic Controls

Topics: Equipment and tools; Checking the control air supply; Output pressure test; Checking for air leaks; Checking other controllers; Actuator problems; Thermostat adjustments

Learning Objectives:

• Describe the symptoms of control air contamination and explain how to remedy it.
• Explain how to check thermostat output pressure.
• List at least three kinds of actuator problems and explain how to solve them.
• Describe the calibration procedure and explain its purpose.
• Explain how to calibrate a pneumatic controller.

Chapter 5: Troubleshooting the Refrigerant Circuit

Topics: Preliminary checks; Analyzing the complaint; Checking refrigerant pressures; Checking refrigerant charge; Checking for refrigerant leaks; Compressor cycling; Checking high-side components; Low-side problems, Distribution problems

Learning Objectives:

• Distinguish between a refrigerant circuit problem and a conditioned-medium problem.
• Explain the procedure for checking refrigerant charge.
• Name major causes of variance in head and suction pressures.
• Explain how to isolate the cause of compressor short cycling.
• Explain how to use head-pressure readings and suction-pressure readings in diagnosing refrigeration problems.

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