Heat Pump Training System

Transcription

1 Refrigeration and HVAC Heat Pump Training System Courseware Sample F0

2 Order no.: First Edition Revision level: 02/2015 By the staff of Festo Didactic Festo Didactic Ltée/Ltd, Quebec, Canada 2007 Internet: Printed in Canada All rights reserved ISBN (Printed version) ISBN (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 available for use on intranet, Internet and LMS platforms and databases such as Moodle, which allow access by a wide variety of users, including those outside of the purchaser's site/location. Entitlement to other rights relating to reproductions, copies, adaptations, translations, microfilming and transfer to and storage and processing in electronic systems, no matter whether in whole or in part, shall require the prior consent of Festo Didactic GmbH & Co. KG. Information in this document is subject to change without notice and does not represent a commitment on the part of Festo Didactic. The Festo materials described in this document are furnished under a license agreement or a nondisclosure agreement. Festo Didactic recognizes product names as trademarks or registered trademarks of their respective holders. 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.

3 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

4 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 did@de.festo.com. The authors and Festo Didactic look forward to your comments.

5 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

6 IV

7 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

8 VI

9 Courseware Outline HEAT PUMP TRAINING SYSTEM Introduction... V Unit 1 Trainer Familiarization Ex. 1-1 Heat Pump Cooling Mode Ex. 1-2 Heat Pump and Electric Heating Cycles Unit 2 Manual Thermostat Operation Ex. 2-1 Manual Thermostat Operation in the Cooling Cycle Ex. 2-2 Manual Thermostat Operation in the Heating Cycle Unit 3 Electric Heating Ex. 3-1 Electric Heating Unit 4 Defrosting Ex. 4-1 Defrosting Unit 5 Programmable Thermostat Operation Ex. 5-1 Programmable Thermostat Operation Ex. 5-2 Programmable Thermostat Operation and Programming Unit 6 Troubleshooting Ex. 6-1 Troubleshooting Appendix A Appendix B Operation of the Four-Way Reversing Valve Four-Way Valve in the Stuck Condition We Value Your Opinion! VII

10

11 Sample Exercise Extracted from Heat Pump Training System

12

13 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

14 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

15 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 V1 V2 V3 V4 CONDITION Closed Open Closed 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

16 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: F ( C) 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 Low side temperature High side temperature Low side pressure (PI1) High side pressure (PI2) F ( C) F ( C) F ( C) psi (kpa) 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

17 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 Low side temperature High side temperature Low side pressure (PI2) High side pressure (PI1) F ( C) F ( C) F ( C) psi (kpa) 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

18 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

19 Instructor Guide Sample Extracted from Heat Pump Training System

20

21 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: 59.3 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) 11

22 Defrosting 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. 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