Troubleshooting Trainer Developed for Mechanical Side

February 23, 2009
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PHOENIX - Refrigeration School Inc. (RSI) has long been dedicated to providing troubleshooting training for students. For instance, in the 1970s, the Phoenix-based school developed the Service Trainer, Air conditioning, Refrigeration (STAR), designed to help students develop electrical troubleshooting skills.

Due largely to this invention, RSI has developed a reputation with employers of being a resource of entry- level technicians with a well-developed set of electrical troubleshooting skills. The school believes it is advancing since it recently developed a prototype machine invented to specifically address troubleshooting related to the mechanical side of an air conditioning system.

With the dual trainers, the school has launched the Binary STAR Troubleshooting System, which encompasses the E-STAR (electrical trainer) and the M-STAR (mechanical trainer).


The M-STAR was invented and built primarily by instructors Richard Kunst, Dave Lloyd, and Edwin Hergert. The process began in 2005. It surfaced after Lloyd’s former colleagues from his days as a technician commented that an RSI graduate could best troubleshoot electrical circuitry in HVACR equipment, but they were not better than anyone else at mechanical troubleshooting.

Lloyd and Kunst got the mechanical ball rolling. The two of them embarked on the project of producing a trainer that would allow an instructor to program multiple problems into a system on which students could practice troubleshooting skills. They wanted students to be able to fix one problem, and have the instructor able to immediately program another problem into the system. In this fashion, the student could experience multiple real-world problems in a short time frame. It was their thinking that skills would be developed not only through discussion but also through frequent repetition.

As the concept developed over a period of over two and a half years, the two would frequently engage Hergert to help work through a concept or particular engineering challenge to ensure the trainer would have the look and feel of a real unit in the field.

The prototype has been a success to date, allowing students to see system failures in real time. The machine will show students actual faults on a real air conditioning system, in real time. To date the unit will simulate a refrigerant restriction, overcharge condition, undercharge condition, thermostatic expansion valve (TXV) overfeed and underfeed, evaporator air flow restriction, high evaporator load, bad compressor valves, and reduced condenser airflow. The symptoms are in real time and the unit reacts much the way the average system will with one of the faults.

“The intent was to give students a firsthand feel for a problem in the same manner as the E-STAR does,” said Kunst, who recently retired from RSI.

The trainer will be capable of showing additional faults, as it is being tweaked and polished further, said Kunst. “Future symptoms will include a high heat load, a low side restriction, and a ‘hunting’ TXV,” he said. “The system has the ability to run as a TXV system or capillary tube system, showing students that faults are not limited to only one type of system. As the trainer becomes an integral part of the school’s training, it will be coupled to a small building that will allow for environmental changes to affect the unit in the same manner in which a unit is affected when attached to a home.”

RSI expects that future renditions of the trainer will be introduced as a heat pump, split system, and other refrigeration equipment. RSI will begin using the M-STAR trainer in the classroom this summer.

RSI was founded in Phoenix in 1965 to meet the growing need for high-quality education and training of air conditioning and refrigeration technicians. RSI was started by family members, with backgrounds in refrigeration and air conditioning.

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Publication date: 02/23/2009

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