heat pump training system
TRANSCRIPT
Refrigeration and HVAC
Heat Pump Training System
Courseware Sample 85143-F0
Order no.: 85143-00
First Edition
Revision level: 02/2015
By the staff of Festo Didactic
© Festo Didactic Ltée/Ltd, Quebec, Canada 2007
Internet: www.festo-didactic.com
e-mail: [email protected]
Printed in Canada
All rights reserved
ISBN 978-2-89640-227-4 (Printed version)
ISBN 978-2-89747-217-7 (CD-ROM)
Legal Deposit – Bibliothèque et Archives nationales du Québec, 2007
Legal Deposit – Library and Archives Canada, 2007
The purchaser shall receive a single right of use which is non-exclusive, non-time-limited and limited
geographically to use at the purchaser's site/location as follows.
The purchaser shall be entitled to use the work to train his/her staff at the purchaser's site/location and
shall also be entitled to use parts of the copyright material as the basis for the production of his/her own
training documentation for the training of his/her staff at the purchaser's site/location with
acknowledgement of source and to make copies for this purpose. In the case of schools/technical
colleges, training centers, and universities, the right of use shall also include use by school and college
students and trainees at the purchaser's site/location for teaching purposes.
The right of use shall in all cases exclude the right to publish the copyright material or to make this
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Information in this document is subject to change without notice and does not represent a commitment on
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Festo Didactic recognizes product names as trademarks or registered trademarks of their respective
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All other trademarks are the property of their respective owners. Other trademarks and trade names may
be used in this document to refer to either the entity claiming the marks and names or their products.
Festo Didactic disclaims any proprietary interest in trademarks and trade names other than its own.
Safety and Common Symbols
The following safety and common symbols may be used in this manual and on the equipment:
Symbol Description
DANGER indicates a hazard with a high level of risk which, if not avoided, will result in death or serious injury.
WARNING indicates a hazard with a medium level of risk which, if not avoided, could result in death or serious injury.
CAUTION indicates a hazard with a low level of risk which, if not avoided, could result in minor or moderate injury.
CAUTION used without the Caution, risk of danger sign , indicates a hazard with a potentially hazardous situation which, if not avoided, may result in property damage.
Caution, risk of electric shock
Caution, hot surface
Caution, risk of danger
Caution, lifting hazard
Caution, hand entanglement hazard
Notice, non-ionizing radiation
Direct current
Alternating current
Both direct and alternating current
Three-phase alternating current
Earth (ground) terminal
Safety and Common Symbols
Symbol Description
Protective conductor terminal
Frame or chassis terminal
Equipotentiality
On (supply)
Off (supply)
Equipment protected throughout by double insulation or reinforced insulation
In position of a bi-stable push control
Out position of a bi-stable push control
We invite readers of this manual to send us their tips, feedback, and suggestions for improving the book.
Please send these to [email protected].
The authors and Festo Didactic look forward to your comments.
III
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
IV
V
Introduction
In all types of refrigeration and air conditioning work, a thorough knowledge of thebasic principles is required. This is particularly true when dealing with heat pumpsystems where both heating and cooling modes of operation must be understood.
The Heat Pump Training System provides the necessary training to develop thestudent’s understanding of typical domestic heat pump systems. A hands-onapproach is taken to train and evaluate the student on the principle componentsused in modern heat pumps. The trainer is designed with a general approach to heatpump 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 whichheat pump systems are most effective.
The Heat Pump Training System utilizes those components that are most commonlyfound on domestic heat pump systems. The student should have a priorunderstanding of the following components before performing the laboratoryprocedures: a standard, hermetically-sealed, compressor designed to operate onR134a refrigerant, thermostatic expansion valves, check valves, capillary tubecontrols, and pressure controllers.
The laboratory procedures for this trainer will introduce and train the student in theoperation of a manual thermostat, programmable thermostat, automatic defrosttimer, four-way reversing valve, and fan/limit temperature sensor. These devices arecommonly used to control domestic heat pump systems.
Fault insertion switches are provided to introduce eighteen distinct electrical faultswhich will develop the student’s troubleshooting skills. The test instrumentation andoperational indicators which are necessary to observe and test the operation of aheat pump system are provided with the trainer.
The student manual is formatted into laboratory exercises and involves the instructoras each exercise is completed. The exercises are organized into a logical orderaccording to the various tasks to be accomplished. Each activity includes aninformation sheet containing a brief discussion, a list of equipment, a discussion, anda step-by-step procedure.
VI
HEAT PUMP TRAINING SYSTEM
Courseware Outline
VII
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!
Sample Exercise
Extracted from
Heat Pump Training System
3
Exercise 4-1
Defrosting
EXERCISE OBJECTIVE
When you have completed this exercise, you will be familiar with the operation of thedefrost cycle on the Heat Pump Training System.
DISCUSSION
The timer used on the HEAT PUMP TRAINER is located in the lower left side of thesystem panel. The automatic defrost timer reverses the refrigerant flow through thesystem at specific time intervals, and for a predetermined period of time. Figure 4-1shows the refrigerant flow during the cooling mode, and Figure 4-2, during thecooling mode defrost cycle.
Figure 4-1. Heat Pump Training System in cooling mode.
Defrosting
4
Figure 4-2. Cooling mode defrost cycle.
Two dials located inside the defrost timer are used to set the current time and thetime at which the defrost cycle will be activated. For purposes of demonstration, thestudent 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. Thelength of time elapsing between two successive defrost cycles can be adjusted bymoving 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 itjust touches the timer pointer. The defrost cycle can be activated using theDEFROST TIMER switch on the CONTROL PANEL. The defrost cycle will then beinitiated within a few minutes.
Defrosting
5
Figure 4-3. Automatic defrost timer dials.
PROCEDURE
Cooling cycle
G 1. To configure the trainer for the cooling mode operation using thermostaticexpansion 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 andclosing V2.
G 2. On the CONTROL PANEL, set the THERMOSTAT switch to MANUAL. Setthe DEFROST TIMER switch in the O (off) position and the DEFROSTTERMINATION switch to the O position. Set the MANUAL THERMOSTATHEATING MODE switch to HEAT PUMP. Finally, set the OUTDOORBLOWER SPEED control knob to HIGH.
Defrosting
6
G 3. Turn the manual thermostat dial fully counterclockwise, which will force thesystem to run continuously. Set the fan control switch to AUTO and theheating/cooling switch to COOL.
Thermostat temperature setpoint: F ( C)
G 4. Connect a temperature sensor to THERMOMETER INPUT A of theCONTROL PANEL, then place the sensor on the programmable thermostatand shut the plastic door.
G 5. Connect two additional temperature sensors to THERMOMETER INPUTSB and C of the CONTROL PANEL. Using velcro strips, install these sensorsso 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 forapproximately 5 minutes.
G 7. Record the room temperature, as well as the temperature at the pressuregauge locations (PI1 and PI2), based on the reading of theTHERMOMETER display of the CONTROL PANEL. Also, record the lowand high side pressures at PI1 and PI2.
Room temperature F ( C)
Low side temperature F ( C)
High side temperature F ( C)
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 thetrainer front panel. Open the cover of the timer, then set the defrost intervaland time of initiation and termination according to the following steps:
– Push down and rotate the defrost duration pointer until it points the30 minutes marking. This sets the defrost interval.
– Get one of the four provided pins and screw it into one of the holes onthe 24 hour timing dial;
– Rotate the two hour dial until the start pin faces the timer pointer (seeFigure 4-3) and the mechanism has made three clicks.
Defrosting
7
G 9. Set the TIMER DEFROST switch to I (on) and wait until the defrost cycleactivates and the INDOOR COIL DEFROST lamp turns on, which will takeabout 15 seconds.
Note: If the defrost cycle won't activate 15 seconds after you setthe TIMER DEFROST switch to I, slowly turn the two-hour dial ofthe timer counterclockwise until the defrost cycle starts.
G 10. Wait for approximately 2 minutes, then record the room temperature, as wellas the temperature at the pressure gauge locations (PI1 and PI2). Also,record the low and high side pressures at PI1 and PI2.
Room temperature F ( C)
Low side temperature F ( C)
High side temperature F ( C)
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. Isthe 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 thedefrost cycle deactivates when the defrost duration adjustment pointerbecomes aligned with the start pin, which corresponds to the end of thedefrost 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 pinfaces 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 andwait for about 1 minute.
Defrosting
8
G 16. Simulate deactivation of the defrost cycle by a temperature or pressuresensor on the indoor coil. To do so, set the DEFROST TERMINATIONswitch to I (on) and then to O (off). Is the defrost cycle deactivated eventhough 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.
Instructor Guide Sample
Extracted from
Heat Pump Training System
11
Exercise 4-1
Defrosting
EXERCISE OBJECTIVE
When the student has completed this exercise, he will have gained familiarity with theoperation 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-wayreversing 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 thestudent wants to observe the defrost cycle since the student cannot wait several hours or daysfor 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: 59.3 F (15.2 C)
Low side temperature: 54.9 F (12.7 C)
High side temperature: 93.4 F (34.1 C)
Low side pressure (PI1): 25 psi (172 kPa)
High side pressure (PI2): 160 psi (1103 kPa)
Defrosting
12
G 10. Room temperature: 68 F (20 C)
Low side temperature: 64.6 F (18.1 C)
High side temperature: 78.8 F (26 C)
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. Thisis indicated by the increase in pressure at gauge PI1, and by the decrease in pressureat gauge PI2.
G 16. The defrost cycle is deactivated even though the defrost interval set on the timer hasnot expired. This happens because in systems using a temperature or pressuresensor, the timer is used to deactivate the defrost cycle only when this cycle lasts forlonger than expected.