Service Technician's and Engineer's Guide to Electricity for Refrigeration, Heating and Air Conditioning: Basic Electric Motors (part 3): Service Calls and Quiz

SERVICE CALL PROTOCOL

All heating, refrigeration, and air-conditioning systems at one time or another will require servicing. There are many types of service procedures that are performed each day for customers by industry technicians. Service procedures often performed by technicians in the industry are pre-season startups, preventive maintenance calls, or inoperative system calls. No matter what the reason for the call, technicians must always keep in mind that they are performing a service for the customer and that without the customer and service calls, there is no need for their company or their job. When customers choose a company to service their heating, refrigeration, and air-conditioning equipment, a great deal of trust and confidence is placed in the company and its employees. The technician must make certain that his or her actions and attitude reinforce the decision that the customer has made. A satisfied customer will do more advertising for the company and technician by word of mouth than many other methods of high-cost advertising. When the customer calls and asks for a specific technician, the technician knows that he or she has impressed the customer and pleased his or her employer.

Most technicians have the technical skills required to diagnose and repair most heating, refrigeration, and air-conditioning system problems. You can be very efficient in repairing the system, but you can still fail to satisfy the customer because of your actions or attitudes. The technician is constantly being evaluated by customers, employers, and coworkers. The customer wants to be treated in a fair and courteous manner while the system problem is being resolved. The employer is concerned about the profit margin and wants the technician to work faster and still maintain a high level of accuracy. Coworkers should be friends, but in many cases conflicts occur over speed of work, callbacks, and pay scales. The technician has a difficult task in keeping his or her customers, employer, and coworkers happy.

One of the most important aspects of the technician’s job is the treatment of the customer. The technician must first treat the customer in a courteous manner. Often this will be difficult because the customer will be angry because of the problems with his or her heating, refrigeration, or air conditioning system. E.g., the customer may have spent a cold, uncomfortable night without heat, or it may be 105°F in the house without air conditioning, or food is spoiling because of an inoperative freezer, or this is a callback, or the cost of the repair is higher than expected. The technician will often have to listen to unhappy customers and try to be understanding even before correcting the problem. The technician must be patient and listen to the customer’s complaint while trying to obtain as much information as possible about the problem. The technician should also avoid disrupting the activities of the customer whenever possible.

The technician’s appearance is of utmost importance because often the technician is judged by this alone. The customer will be much more comfortable with a technician who is clean and neat in appearance. Often, because of the location and service procedure, it will be difficult to maintain a clean and neat appearance the entire day. It is the responsibility of the technician to try to remain clean and neat regardless of the working conditions (under houses, in attics, or in muddy, sloppy conditions). Changing a compressor, cleaning a furnace, or cleaning a dirty condenser can make it difficult to remain clean and neat. Many companies require employees to wear uniforms for this purpose. It isn't practical to change clothes every time you work in dirty areas or work with dirty components, but you must do everything possible to maintain a neat and clean appearance at all times.

The technician must treat the customer’s property with respect. The technician will be required to work in close proximity to walls and floor coverings and must do so without marring or damaging these surfaces. Every effort must be made to prevent any type of damage to the customer’s structure or furnishings; make sure hands are clean before working on a thermo stat mounted on an interior wall, remove mud from shoes or remove shoes before entering the structure, dust clothing before entering the structure, and don't use furniture as a resting place for tools or components. It is the technician’s responsibility to prevent damage to the customer’s property. Damage to the customer’s structure or furnishings will have to be corrected by the company. Most companies have liability insurance to cover such costs. The technician should also make certain to check the service procedures performed to ensure that no danger exists from gas leaks, loose wires, or fire in the equipment that was serviced.

Upon completion of the service procedure, the technician should fully explain the problem and the service performed to correct it. If there are several options for correcting the problem, all options should be discussed and the customer allowed to choose the option he or she prefers. The technician should be fair about the amount of time spent and parts used for which the customer will be billed. E.g., it's unfair to bill the customer for 10 pounds of refrigerant when only 5 were required; it would also be unfair to bill the customer for more time than was required. It is also dishonest to replace parts that are still in good condition and charge the customer for them. The technician must always make the correct ethical decisions regarding the customer to ensure continued trust.

The technician should never forget that the company will be judged by the technician’s actions, appearance, and attitude. No greater compliment can be paid a service technician than for the customer to call back and request a particular technician for a service call.

SERVICE CALLS

Service Call 1

Application: Residential conditioned air system

Type of Equipment: Gas-fired forced-air furnace

Complaint: No heat

Service Procedure:

1. The technician reviews the work order from the dispatcher for avail able information. The work order information reveals that the furnace is an up-flow gas-fired furnace located in a closet within the living space of the residence.

2. The technician informs the customer of his or her presence (if the customer is available) and obtains specifics about what the system is doing.

3. Upon entering the residence, the technician makes certain that no dirt or foreign material are carried into the structure. The technician also takes care not to mar interior walls.

4. The customer informs the technician that the main burner is igniting and operating for several minutes and cutting off. The blower isn't operating.

5. The technician checks the limit and fan controls and determines that they are operating correctly. The technician checks the voltage avail able to the fan motor and determines that the voltage supply is correct.

6. The technician turns the power supply off and locks or labels it.

7. The fan motor is only moderately warm, indicating that the motor has been off for some time.

8. The technician checks the motor windings with an ohmmeter and reads infinite resistance, determining that the motor windings are open.

9. The technician changes the fan motor and checks the operation of the furnace.

10. The technician informs the customer of the problem and that it has been corrected.

11. A subsequent courtesy call by the technician to the customer to make certain the equipment is operating properly builds confidence and good will between the company and the customer.

Service Call 2

Application: Commercial refrigeration (walk-in cooler)

Type of Equipment: Air-cooled condensing unit with evaporator

Complaint: Warm walk-in cooler

Service Procedure:

1. The technician reviews the work order from the dispatcher for available information. The work order information reveals that the temperature of the walk-in cooler is above a safe temperature for the stored product

2 The technician informs the business manager of his or her presence and obtains specifics about what the refrigeration unit system is doing.

3 Upon entering the business, the technician makes certain that the normal business activities are not interrupted and that his or her appearance is clean and neat.

4 The manager informs the technician that the refrigeration unit's not maintaining the correct temperature

5 The technician makes a visual inspection of the indoor unit and finds the evaporator fan motor operating.

6 The technician proceeds to the outdoor condensing unit and observes that the compressor runs only a short period of time and cuts off. The condenser fan motor isn't running.

7. With the compressor running, the technician knows that power is available to the condensing unit.

8. The technician turns the power off to the condensing unit and locks or labels it.

9. The technician finds that the motor turns freely but is extremely hot. The technician makes the determination that the motor bearings are good.

10. The technician determines that the condenser fan motor is a PSC motor and checks the running capacitor with an ohmmeter or capacitor tester. The technician finds that the capacitor is open.

11. The technician removes the faulty running capacitor and replaces it with the correct replacement capacitor.

12. The technician restores power to the condensing unit, observes the operation of the fan motor, then checks the amp draw of the motor and compares the reading with the nameplate running ampacity of the motor to ensure that the motor is operating properly.

13. The technician interrupts power to the unit and oils the condenser fan motor.

14. The technician informs the manager of the problem and that it has been corrected.

15. A subsequent courtesy call by the technician to the manager to make certain the equipment is operating properly builds confidence and good will between the service company and the customer.

Service Call 3

Application: Residential conditioned air system

Type of Equipment: Packaged heat pump

Complaint: No cooling

Service Procedure:

1. The technician reviews the work order from the dispatcher for avail able information. The work order information reveals that the unit's a packaged heat pump. The customer will leave the key under a flower pot on the right side of the front door.

2. Upon entering the residence, the technician makes certain that no dirt or foreign material is carried into the structure. The technician also takes care not to mar interior walls.

3. The technician sets the thermostat to cool and observes the operation of the equipment. The technician immediately notices that the indoor fan motor isn't operating.

4. The technician goes outside to check the unit, specifically the indoor fan motor, based on the indication that the motor isn't running when the thermostat is set to cool. The technician finds that the compressor and outdoor fan motor are operating, but the indoor fan motor isn't operating.

5. The technician turns the power supply off and locks or labels it.

6. The technician removes the unit cover, allowing access to the indoor fan motor.

7. The technician finds that the indoor fan turns with difficulty and the motor is hot to the touch.

8. The technician has determined by the fan being difficult to turn that the bearings are bad and that the indoor fan motor should be replaced. (Occasionally, oiling the motor will free the bearings, but this is usually only a temporary correction and , in most cases, the best solution is to replace the motor.)

9. The technician replaces the fan motor with the correct motor.

10. The technician turns the power on and checks the operation and amp draw of the new fan motor. The indoor fan motor is operating properly, so the technician turns the power off and replaces the access cover.

11. The technician turns the power on to the unit.

12. The technician returns the thermostat setting to normal and leaves a note for the customer indicating the service performed.

13. The technician replaces the key in the location designated by the customer.

Service Call 4

Application: Commercial conditioned air system

Type of Equipment: Commercial and industrial fan coil unit with 230-volts—three-phase—60-hertz power supply

Complaint: Blower motor does not operate

Service Procedure:

1. The technician reviews the work order from the dispatcher for avail able information. The work order information reveals that the motor operating the blower in the fan coil unit's not operating.

2. The technician informs the maintenance supervisor of his or her presence and obtains any specific information about the fan coil unit.

3. The technician visually observes the blower motor and controls and finds that the motor is controlled by a magnetic starter, which has opened due to a possible overload. The technician resets the overload and the blower motor rotates at a very low rate of speed, and then the magnetic starter opens again due to an overload.

4. The technician turns the power off and locks or labels it.

5. The technician checks the motor and finds that it turns freely but is extremely hot to the touch.

6. The technician has determined that the bearings of the motor are good and the overheating is due to other factors.

7. The technician checks the power at the magnetic starter and finds that only single phase is available and that the motor requires 230 volts— three phase—60 hertz.

8. The technician checks the voltage at the distribution center and checks the fuses with an ohmmeter. One of the three fuses has an infinite reading and is bad.

9. The technician replaces the bad fuse with one of equal specification.

10. The technician restores power to the magnetic starter and observes that the fan operates.

11. The technician checks the amp draw of the fan motor and determines that the motor is operating properly.

12. The maintenance supervisor is informed that the problem was a blown fuse that created a single-phasing condition and overloaded the motor, and that the problem has been corrected.

Service Call 5

Application: Residential conditioned air system

Type of Equipment: Air-cooled condensing unit

Complaint: No cooling

Service Procedure:

1. The technician reviews the work order from the dispatcher for avail able information. The work order reveals that the system isn't cooling.

2 The technician informs the customer of his or her presence and obtains specifics about what the conditioned air system is doing

3 Upon entering the residence, the technician makes certain that no dirt or foreign material is carried into the structure. The technician also takes care not to mar interior walls

4 The thermostat is set to the cool position and the indoor fan motor is operating, but the system isn't cooling

5 The technician proceeds to the air-cooled condensing unit and finds that the condenser fan motor is operating, which normally indicates that the contactor is closed.

6. The cover is removed from the condensing unit and the technician determines that the compressor isn't operating and is very hot to the touch.

7. A voltage check is made at the compressor terminals and the correct voltage is available.

8. The technician makes a resistance check of the compressor motor and reads 25 ohms between the start and run terminals of the compressor but reads infinite resistance between common and start and common and run. These resistance readings indicate that the internal overload of the compressor is open (it's not allowing voltage to reach the windings).

9. All starting components and capacitors are checked by the technician. If all are good, the technician will have to allow the internal overload ample time to close. After the internal overload has reset, the technician will make a resistance check of the windings. The resistance reading of the run to start terminals of the compressor should equal the readings of the sum of the common to start and common to run terminals.

10. The windings are good, so the technician tries to start the compressor. If the compressor fails to start and pulls a high current draw or the internal overload opens again, the compressor is probably mechanically seized or locked down.

11. The technician informs the customer that the compressor is bad and will have to be replaced. The technician gives the homeowner an estimate of the replacement cost and time when the replacement can be made.

Service Call 6

Application: Residential conditioned air system

Type of Equipment: Heat pump

Complaint: No heat Service Procedure:

1. The technician reviews the work order from the dispatcher for available information. The work order indicates that the breaker for the outdoor section of the heat pump is overloading, while the indoor unit's operating. The customer will leave the key under the mat at the back door.

2. Upon entering the residence, the technician makes certain that no dirt or foreign material is carried into the structure. The technician also takes care not to mar interior walls.

3. The technician sets the thermostat to heat and observes the operation of the equipment. The technician notices that the indoor fan motor is operating, but the unit's not heating.

4. The technician goes to the outdoor unit and observes that the unit's not operating. The voltage is checked at the line connections of the disconnect switch of the outdoor unit and no voltage is available. The disconnect is turned off. The technician locates the electrical panel and resets the breaker that feeds the outdoor unit.

5. The disconnect is closed and nothing happens. A voltage check is again made, which indicates that the breaker has broken the circuit again.

6. The technician determines that a short circuit exists somewhere in the outdoor unit. A resistance check must be made of each load that receives voltage from the disconnect. The resistance checks indicate that the resistance reading from the common to run terminals of the compressor is 0 ohm. This indicates that the compressor motor windings are shorted and the compressor must be replaced.

7. The customer is informed that the compressor is bad and will have to be replaced. The technician gives the homeowner an estimate of the replacement cost and a time when the replacement can be made.

SUMMARY

The single most important operating principle of an electric motor is the rotating magnetic field produced by alternating current. An alternating cur rent is applied to the stator of the motor to produce a magnetic field. The magnetic field interacts with the rotor to produce a magnetic field in the rotor. When these two magnetic fields act together, they produce a rotating movement in the motor.

There are basically six types of motors used in the industry: shaded pole, split phase, permanent split capacitor, capacitor start—capacitor run and capacitor start, three phase, and electronically commutated.

The shaded-pole motor is a low-starting torque motor used on some propeller types of fans. These motors are easy to identify because of the cop per band around the shaded pole. They are easily diagnosed for trouble because of their simple winding patterns.

Split-phase motors are relatively low-torque motors. They are simple and inexpensive devices. A split-phase motor can be used on a small hermetic compressor with the starting winding being dropped out by a starting relay. It can be used with any open types of motors that don't require a high starting torque.

The permanent split-capacitor motor has a low starting torque and a running capacitor in the starting winding. The running capacitor remains in the circuit at all times to produce good running efficiency. The permanent split-capacitor motor is used on most residential air conditioners of 5 horse power or under and on direct-drive fan motors. It is relatively inexpensive because it does not have a switch to drop the starting winding.

The capacitor-start and the capacitor-start—capacitor-run motors are similar in design. They have a high starting torque. The addition of a running capacitor to a capacitor-start motor produces the capacitor-start—capacitor- run motor, which has good running efficiency.

Three-phase motors are commonly used on large pieces of equipment. They operate much like single-phase motors except that they have three basic phase displacements without the use of any starting apparatus. They have better starting and running characteristics than single-phase motors.

The electronically commutated motor (ECM) is a high-efficiency, variable-speed motor that's interfaced with system controls. The ECM can be programmed to maintain constant airflow over a wide range of external static pressures. The ECM is constructed as a three-phase DC motor. The motor is made in two parts: One part is the motor and the other section is the controller. The motor can be disconnected and checked just like a three-phase motor. The controller/module can easily be checked with a motor analyzer purchased from the manufacturer.

Hermetic compressor motors are becoming popular because of their low cost. They are used in many cooling units, especially for the smaller systems. Hermetic motors must have all their starting apparatus wired and mounted externally because it cannot be contained in the compressor shell. A hermetic compressor motor may be any one of the five basic motor types discussed in this section. The enclosure distinguishes the hermetic compressor from the other motor types.

Most single-phase motors require some method of producing a second phase of electricity in the motor to make it start. The design of the windings in a split-phase motor allows the use of a centrifugal switch to drop the starting winding out of the circuit after the motor has attained 75% of its full speed. Other types of single-phase motors use capacitors to create the second phase. The permanent split-capacitor motor incorporates a run- fling capacitor to aid in the starting of the motor. The capacitor-start— capacitor-run motor incorporates the running capacitor along with a starting capacitor, using a potential relay to drop out the starting capacitor. The capacitor-start motor operates as a split-phase motor except that a starting capacitor is added to the start winding.

The service technician will often need to diagnose why a hermetic compressor won't run. Frequently, the fault lies in the hermetic motor. Hermetic compressor motors can easily be diagnosed with a good ohmmeter as open, shorted, or grounded. Spot burnouts are harder to diagnose, but you can still identify them easily by using the resistance readings of the motor.

CAUTION: All electric motors should be properly grounded.

CAUTION: Before starting an electric motor that has blown a fuse or tripped a circuit breaker, make sure that the motor does not have a short to ground before resetting or replacing the safety device.

REVIEW QUIZ

1. What is magnetism?

2. Torque is _________

a. strength that a motor produces by turning

b. rotating motion

c. a motor under load

d. all of the above

3. A magnetic field is __________

a. the area around an electric motor

b. the area around an electric wire

c. the area in which a magnetic force operates

d. all of the above

4. True or False: A permanent magnet is a piece of material that has been magnetized and can hold its magnetic strength for a reasonable length of time.

5. How is an electromagnet produced?

6. Which of the following produces the best electromagnet?

a. cobalt

b. soft iron

c. paper

d. wood

7. Unlike poles of a magnet _________ each other and like poles each other.

8. What part does polarity play in the operation of an electric motor?

9. What part of a motor produces an inductive magnetic field within itself to facilitate the rotating motion?

a. squirrel cage rotor

b. motor bearings

c. capacitor

d. all of the above

10. What part does the frequency of alternating current play in the operation of an electric motor?

11. What would be the speed of a two-pole motor if there were 7200 flow reversals per minute?

a. 1100rpm

b. 1800 rpm

c. 2800 rpm

d. 3600rpm

12. What are the five types of single-phase motors used in the industry?

13. Which of the following correctly lists the motor’s starting torque from lowest to highest?

a. capacitor start, split phase, shaded pole, three phase

b. shaded pole, three phase, permanent split capacitor, capacitor start

c. three phase, split phase, shaded pole, capacitor start

d. shaded pole, split phase, capacitor start, three phase

14. Which of the following is a common use of a shaded-pole motor?

a. furnace fan motor

b. propeller fans

c. small pumps

d. compressors

15. How does a shaded-pole motor operate?

16. How can a shaded-pole motor be reversed?

17. What determines the rotation of a shaded-pole motor?

a. location of windings

b. location of shaded pole

c. location of rotor

d. none of the above

18. Draw a diagram of a three-speed, shaded-pole motor.

19. What enables a split-phase motor to develop enough torque to begin rotation?

20. What removes the starting winding from the electrical circuit of an open-type split-phase motor once it reaches 75% of its operating speed?

a. disconnect switch

b. phase-out switch

c. centrifugal switch

d. starting switch

21. What are the three probable areas of trouble in a split-phase motor?

22. What is the unit of measurement for the strength of a capacitor?

a. micro-amp

b. micro-torque

c. microfarad

d. microwatt

23. What is the purpose of a capacitor?

a. boost starting torque

b. increase running efficiency

c. increase motor speed

d. both a and b

24. What is the difference between a running and a starting capacitor?

25. List the five capacitor replacement rules.

26. Explain the operation of a permanent split-capacitor motor.

27. How are a PSC motor and a capacitor start—capacitor-run motor similar?

a. Both use a starting capacitor.

b. Both use a running capacitor.

c. Both use starting relays.

d. none of the above

28. What are the advantages and disadvantages of using the following types of motors?

a. shaded-pole motor

b. PSC motor

c. split-phase motor

d. capacitor-start-capacitor-run motor

29. What are the similarities between an open-type split-phase motor and a capacitor-start motor?

a. Both have a capacitor.

b. Both have a relay.

c. Both have a centrifugal switch.

d. none of the above

30. Which of the following is an advantage in using a three-phase motor?

a. higher starting torque

b. stronger

c. more dependable

d. all of the above

31. Draw a wiring diagram of a capacitor-start—capacitor-run motor.

32. True or False: All starting apparatuses are mounted externally to the hermetic compressor shell.

33. What is the process in troubleshooting any electric motor?

34. Which of the following is the capacitance of an 88- and a 108- starting capacitor connected in series?

a. 196 uF

b. 96 uF

c. 48 uF

d. 40 uF

35. Which of the following is the capacitance of two 20-pP running capacitors connected in parallel?

a. 10 uF

b. 20 uF

c. 30 uF

d. 40 uF

36. If a capacitor produces 15 A on a 240-volt supply, which of the following is its microfarad rating?

a. 166 uF

b. 15 uF

c. 200 uF

d. 3450 uF

37. Which of the following capacitors could be used to replace a 35-uF, 370-V running capacitor?

a. 35 uF, 330V

b. 35 uF,390V

c. 30 uF,440V

d. 40 uF,370V

38. Which of the following capacitors could be used to replace a 188-uF, 250-V starting capacitor?

a. 188 uF, 120V

b. 259 uF, 120V

c. 200 uF, 250V

d. 300 uF, 250V

39. Which of the following capacitors or combination of capacitors could be used to replace a 45- 370-V running capacitor?

a. 40 uF, 440 V

b. 30 uF, 250V

c. 30 uF

d. 15 uF, 440 V

40. Which of the following capacitors or combination of capacitors could be used to replace an 88-uF, 250-V starting capacitor?

a. 180 uF,250V

b. 180 uF, 330 V

c. 150 uF, 120V

d. 150 uF,250V

41. Find the common, start, and run terminals of the following hermetic compressors.

elec-refridge_9-Q41.jpg

42. Briefly explain the procedure for troubleshooting hermetic compressor motors.

43. What are the electrical failure categories for hermetic compressor motors?

44. What precautions should be taken when checking hermetic compressor motors?

45. What would be the highest allowable resistance reading for a grounded compressor motor?

46. What are the advantages of using an electronically commutated motor over a PSC motor?

47. Explain the construction of an ECM.

48. An ECM is a ___________

a. three-phase, AC motor

b. three-phase, DC motor

c. single-phase, AC motor

d. single-phase, DC motor

49. True or False: The resistance readings of the windings of a properly operating ECM should be equal.

50. True or False: The line voltage power supply of an ECM should never be disconnected or connected with the power on.

PRACTICE SERVICE CALLS

Determine the problem and recommend a solution for the following ser vice calls. (Be specific; don't list components as good or bad.)

Practice Service Call 1

Application: Residential conditioned air system

Type of Equipment: Packaged heat pump

Complaint: Intermittent heat

Symptoms:

1. All components of equipment are operating properly except the indoor fan motor.

2. Indoor fan motor is turning slower than normal.

3. Indoor fan motor is drawing 12 amps (nameplate amps 3.2 A).

4. Indoor fan motor cuts off approximately every 10 minutes for a con siderable period of time.

5. Ohmmeter reading of run winding is 2 ohms.

6. Ohmmeter reading of start winding is 12 ohms.

7. Ohmmeter reading of capacitor is infinite.

Practice Service Call 2

Application: Commercial refrigeration (walk-in freezer)

Type of Equipment: Air-cooled condensing unit with evaporator (unit voltage 240 V— 10—60 Hz)

Complaint: No refrigeration

Symptoms:

1. Compressor is out due to opening of high-pressure switch. (Technician resets high-pressure switch.)

2. Compressor operates after resetting the high-pressure switch, but the condenser fan motor does not operate.

3. The condenser fan motor is cold to the touch.

4. Voltage to the condenser fan motor is 240 volts.

5. Ohm reading of the start winding of the condenser fan motor is 0 ohms.

Practice Service Call 3

Application: Commercial and industrial conditioned air system

Type of equipment: Commercial and industrial fan coil unit (unit voltage 240 V—3Ø—60 Hz)

Complaint: Fan does not operate

Symptoms:

1. Motor is supplied with 240 V—3ø—60 Hz.

2. Resistance reading of motor is between T and T and T and T = infinite ohms, T and T = 2 ohms, and T and T = infinite ohms. (Motor is dual voltage, wye winding.)

3. Motor is cold to the touch.

Practice Service Call 4

Application: Domestic refrigeration

Type of Equipment: Frost-free refrigerator

Complaint: No refrigeration

Symptoms:

1. Compressor does not run.

2. Compressor starting components are good.

3. Resistance readings of compressor terminals are: C to S = 12 ohms, C to R =0 ohms, and S to R =0 ohms.

Practice Service Call 5

Application: Residential conditioned air system

Type of Equipment: Gas furnace with air-cooled condensing unit

Complaint: No cooling

Symptoms:

1. Indoor fan is operating normally.

2. Condenser fan motor is operating normally.

3. Compressor is extremely hot to the touch.

4. Resistance readings of the compressor terminals are: C to R = 2 ohms, C to S = 13 ohms, and R to S = 15 ohms.

5. Resistance reading between the run terminal and compressor housing 200 ohms.

Practice Service Call 6

Application: Residential conditioned air system

Type of Equipment: Air-cooled packaged unit

Complaint: No cooling

Symptoms:

1. Indoor fan motor is operating normally.

2. Condenser fan motor is operating normally.

3. Compressor is extremely hot to the touch.

4. Resistance readings of the compressor terminals are: R to S = 15 ohms and C to R and S = infinity.

5. All capacitors and starting components are good.

6. Compressor cools and upon supplying power has a current draw of 85 amps (nameplate full load amps = 24 A).