A Courseware Sample Refrigeration, Air Conditioning, and Heating

Refrigeration, Air Conditioning,
and Heating
Courseware Sample
85143-F0
A
REFRIGERATION, AIR CONDITIONING,
AND HEATING
COURSEWARE SAMPLE
by
the Staff
of
Lab-Volt Ltd.
Copyright © 2008 Lab-Volt Ltd.
All rights reserved. No part of this publication may be reproduced,
in any form or by any means, without the prior written permission
of Lab-Volt Ltd.
Printed in Canada
April 2008
Table of Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V
Courseware Outline
Heat Pump Training System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VII
Sample Exercise Extracted from Heat Pump Training System
Ex. 4-1
Defrosting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Instructor Guide Sample Extracted from Heat Pump Training System
Ex. 4-1
Defrosting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
III
IV
Introduction
In all types of refrigeration and air conditioning work, a thorough knowledge of the
basic principles is required. This is particularly true when dealing with heat pump
systems where both heating and cooling modes of operation must be understood.
The Heat Pump Training System provides the necessary training to develop the
student’s understanding of typical domestic heat pump systems. A hands-on
approach is taken to train and evaluate the student on the principle components
used in modern heat pumps. The trainer is designed with a general approach to heat
pump systems which may be applied to many of the popular systems in use today.
The trainer will demonstrate the functions and applications of heat pump principles,
which in turn will develop the student’s understanding of the conditions under which
heat pump systems are most effective.
The Heat Pump Training System utilizes those components that are most commonly
found on domestic heat pump systems. The student should have a prior
understanding of the following components before performing the laboratory
procedures: a standard, hermetically-sealed, compressor designed to operate on
R134a refrigerant, thermostatic expansion valves, check valves, capillary tube
controls, and pressure controllers.
The laboratory procedures for this trainer will introduce and train the student in the
operation of a manual thermostat, programmable thermostat, automatic defrost
timer, four-way reversing valve, and fan/limit temperature sensor. These devices are
commonly used to control domestic heat pump systems.
Fault insertion switches are provided to introduce eighteen distinct electrical faults
which will develop the student’s troubleshooting skills. The test instrumentation and
operational indicators which are necessary to observe and test the operation of a
heat pump system are provided with the trainer.
The student manual is formatted into laboratory exercises and involves the instructor
as each exercise is completed. The exercises are organized into a logical order
according to the various tasks to be accomplished. Each activity includes an
information sheet containing a brief discussion, a list of equipment, a discussion, and
a step-by-step procedure.
V
VI
Courseware Outline
HEAT PUMP TRAINING SYSTEM
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V
Unit 1 Trainer Familiarization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
Ex. 1-1
Heat Pump Cooling Mode . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5
Ex. 1-2
Heat Pump and Electric Heating Cycles . . . . . . . . . . . . . . . 1-9
Unit 2 Manual Thermostat Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
Ex. 2-1
Manual Thermostat Operation in the Cooling Cycle . . . . . . 2-3
Ex. 2-2
Manual Thermostat Operation in the Heating Cycle . . . . . . 2-7
Unit 3 Electric Heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
Ex. 3-1
Electric Heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3
Unit 4 Defrosting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
Ex. 4-1
Defrosting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
Unit 5 Programmable Thermostat Operation . . . . . . . . . . . . . . . . . . . . . . . 5-1
Ex. 5-1
Programmable Thermostat Operation . . . . . . . . . . . . . . . . . 5-3
Ex. 5-2
Programmable Thermostat Operation
and Programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7
Unit 6 Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1
Ex. 6-1
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3
Appendix A
Operation of the Four-Way Reversing Valve
Appendix B
Four-Way Valve in the Stuck Condition
We Value Your Opinion!
VII
Sample Exercise
Extracted from
Heat Pump Training System
Exercise
4-1
Defrosting
EXERCISE OBJECTIVE
When you have completed this exercise, you will be familiar with the operation of the
defrost cycle on the Heat Pump Training System.
DISCUSSION
The timer used on the HEAT PUMP TRAINER is located in the lower left side of the
system panel. The automatic defrost timer reverses the refrigerant flow through the
system at specific time intervals, and for a predetermined period of time. Figure 4-1
shows the refrigerant flow during the cooling mode, and Figure 4-2, during the
cooling mode defrost cycle.
Figure 4-1. Heat Pump Training System in cooling mode.
3
Defrosting
Figure 4-2. Cooling mode defrost cycle.
Two dials located inside the defrost timer are used to set the current time and the
time at which the defrost cycle will be activated. For purposes of demonstration, the
student will readjust the defrost timer each time he wants to observe a defrost cycle,
so that he will not have to wait several hours for the timer to actuate the cycle. The
length of time elapsing between two successive defrost cycles can be adjusted by
moving the START PINS on the outer timing (24 HRS) dial, as Figure 4-3 shows.
The student will place these start pins and rotate the two hour (2-HRS) dial until it
just touches the timer pointer. The defrost cycle can be activated using the
DEFROST TIMER switch on the CONTROL PANEL. The defrost cycle will then be
initiated within a few minutes.
4
Defrosting
Figure 4-3. Automatic defrost timer dials.
PROCEDURE
Cooling cycle
G
1. To configure the trainer for the cooling mode operation using thermostatic
expansion valve control, set the manual valves as in Table 4-1.
VALVE
CONDITION
V1
Closed
V2
Open
V3
Closed
V4
Open
Table 4-1. Cooling mode using thermostatic expansion valve.
Note: Capillary tube control may be achieved by opening V1 and
closing V2.
G
2. On the CONTROL PANEL, set the THERMOSTAT switch to MANUAL. Set
the DEFROST TIMER switch in the O (off) position and the DEFROST
TERMINATION switch to the O position. Set the MANUAL THERMOSTAT
HEATING MODE switch to HEAT PUMP. Finally, set the OUTDOOR
BLOWER SPEED control knob to HIGH.
5
Defrosting
G
3. Turn the manual thermostat dial fully counterclockwise, which will force the
system to run continuously. Set the fan control switch to AUTO and the
heating/cooling switch to COOL.
Thermostat temperature setpoint:
EF (EC)
G
4. Connect a temperature sensor to THERMOMETER INPUT A of the
CONTROL PANEL, then place the sensor on the programmable thermostat
and shut the plastic door.
G
5. Connect two additional temperature sensors to THERMOMETER INPUTS
B and C of the CONTROL PANEL. Using velcro strips, install these sensors
so as to read the temperature at the pressure gauge locations (PI1 and PI2).
G
6. Set the POWER switch to the I (on) position. Allow the system to operate for
approximately 5 minutes.
G
7. Record the room temperature, as well as the temperature at the pressure
gauge locations (PI1 and PI2), based on the reading of the
THERMOMETER display of the CONTROL PANEL. Also, record the low
and high side pressures at PI1 and PI2.
Room temperature
EF (EC)
Low side temperature
EF (EC)
High side temperature
EF (EC)
Low side pressure (PI1)
psi (kPa)
High side pressure (PI2)
psi (kPa)
Defrost Cycle
G
8. Locate the AUTOMATIC DEFROST TIMER in the lower left section of the
trainer front panel. Open the cover of the timer, then set the defrost interval
and time of initiation and termination according to the following steps:
–
Push down and rotate the defrost duration pointer until it points the
30 minutes marking. This sets the defrost interval.
–
Get one of the four provided pins and screw it into one of the holes on
the 24 hour timing dial;
Rotate the two hour dial until the start pin faces the timer pointer (see
Figure 4-3) and the mechanism has made three clicks.
–
6
Defrosting
G
9. Set the TIMER DEFROST switch to I (on) and wait until the defrost cycle
activates and the INDOOR COIL DEFROST lamp turns on, which will take
about 15 seconds.
Note: If the defrost cycle won't activate 15 seconds after you set
the TIMER DEFROST switch to I, slowly turn the two-hour dial of
the timer counterclockwise until the defrost cycle starts.
G 10. Wait for approximately 2 minutes, then record the room temperature, as well
as the temperature at the pressure gauge locations (PI1 and PI2). Also,
record the low and high side pressures at PI1 and PI2.
Room temperature
EF (EC)
Low side temperature
EF (EC)
High side temperature
EF (EC)
Low side pressure (PI2)
psi (kPa)
High side pressure (PI1)
psi (kPa)
G 11. Compare the pressures recorded in step 10 to those recorded in step 7. Is
the direction of refrigerant flow reversed when the defrost cycle is activated?
Explain.
G 12. On the timer, turn the two hour dial counterclockwise and observe that the
defrost cycle deactivates when the defrost duration adjustment pointer
becomes aligned with the start pin, which corresponds to the end of the
defrost interval. Record below if you observe this.
G 13. Set the TIMER DEFROST switch to O (off).
G 14. On the timer, rotate the two-hour dial counterclockwise until the start pin
faces the timer pointer and the mechanism has made three clicks.
G 15. Set the TIMER DEFROST switch to I (on) to activate the defrost cycle and
wait for about 1 minute.
7
Defrosting
G 16. Simulate deactivation of the defrost cycle by a temperature or pressure
sensor on the indoor coil. To do so, set the DEFROST TERMINATION
switch to I (on) and then to O (off). Is the defrost cycle deactivated even
though the defrost interval set on the timer has not expired? Explain.
G 17. Set the DEFROST TIMER switch to O (off).
G 18. Turn the POWER switch of the trainer to the O (off) position.
G 19. Unscrew the timer pin and return it to the storage location.
8
Instructor Guide Sample
Extracted from
Heat Pump Training System
Exercise
4-1
Defrosting
EXERCISE OBJECTIVE
When the student has completed this exercise, he will have gained familiarity with the
operation of the defrost cycle on the HEAT PUMP TRAINING SYSTEM.
PROCEDURE INFORMATION
The defrost control on the trainer reverses the refrigerant flow by adjusting the four-way
reversing valve for a set length of time as determined by the defrost timer.
The defrost timer on the HEAT PUMP TRAINING SYSTEM must be adjusted each time the
student wants to observe the defrost cycle since the student cannot wait several hours or days
for the timer to actuate the cycle.
DEMONSTRATION
1. Demonstrate the correct adjustment and operation of the defrost timer.
ANSWERS TO PROCEDURE STEP QUESTIONS
G
7. Room temperature: 59.3EF (15.2EC)
Low side temperature: 54.9EF (12.7EC)
High side temperature: 93.4EF (34.1EC)
Low side pressure (PI1): 25 psi (172 kPa)
High side pressure (PI2): 160 psi (1103 kPa)
11
Defrosting
G 10. Room temperature: 68EF (20EC)
Low side temperature: 64.6EF (18.1EC)
High side temperature: 78.8EF (26EC)
Low side pressure (PI2): 40 psi (276 kPa)
High side pressure (PI1): 125 psi (862 kPa)
G 11. The direction of refrigerant flow is reversed when the defrost cycle is activated. This
is indicated by the increase in pressure at gauge PI1, and by the decrease in pressure
at gauge PI2.
G 16. The defrost cycle is deactivated even though the defrost interval set on the timer has
not expired. This happens because in systems using a temperature or pressure
sensor, the timer is used to deactivate the defrost cycle only when this cycle lasts for
longer than expected.
12