e 20 hvacr volume1 excerpt

Technical Training Associates Presents

20 HVACR

TROUBLESHOOTING

Problems

By Jim Johnson

A Practical Approach To Troubleshooting HVACR Equipment

(Scroll Down For Excerpt)

20 HVACR Troubleshooting Problems By Jim Johnson

HC 70 Box 3172

Sahuarita, AZ 85629

(520) 625-6847

www.technicaltrainingassoc.com

All digital copyrights reserved. Permission is granted by the publisher to print and photocopy the material herein for the purpose of conducting individual training sessions. Distribution of hard copy versions to the public for sale, or digital copying of any and all information contained herein is prohibited.

This troubleshooting handbook contains 20 separate troubleshooting scenarios designed to test the skills of HVACR technicians. In each situation, all the information necessary to arrive at a diagnosis is provided.

The solutions to the problems are presented in a separate section at the end of the book.

If you are working individually with this handbook, use it to test yourself. Review the problem and any related graphics or wiring diagrams, then, record your diagnosis before checking your answer in the solutions section.

If you are a service manager conducting in-house training sessions, or an instructor facilitating a classroom or lab training exercise, you may print and photocopy the problems and diagrams for classroom distribution. Digital copying of this CD is prohibited as noted in the copyright notice above.

Troubleshooting Problem #8

In this troubleshooting situation, you have been called to a restaurant to check an ice machine that, according to the customer, "isn’t dispensing cubes properly."

When you arrive, you find that the unit you’re dealing with is a 240-volt, single-phase machine that employs a remote condenser. The wiring diagram in Figure One shows you the electrical system.

Problem #8 Figure One

Upon your initial evaluation of the machine, you find:

The refrigeration system is operating properly and the unit has no problem manufacturing cubes.

There is no problem with the quality or filtration of the water supply to the machine.

This particular machine uses a small air compressor to momentarily provide a small amount of air to assist in freeing the cubes from the evaporator in the harvest mode.

Upon further review of the schematic diagram and evaluation of the equipment, you note:

That this model employs a control board containing a series of relays that make and break circuits to various components during the freeze and harvest cycles.

That during the harvest sequence implemented by the control board, the water purge, water pump, harvest valve, water valve, dump valve and contactor control system function normally.

There is no air from the air compressor and no voltage is read at any time at the 25/26 connector.

Your troubleshooting question: Which component needs to be replaced?

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