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ABSA 4b Exam 2025 | Actual Exam Questions and
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Which of the following statements about the economisers is false? a) It controls the flow of liquid refrigerant from the low pressure evaporator to the high pressure condenser. b) It is composed of two chambers. c) The upper float chamber is connected to the bottom of the condenser. d) The economiser float chamber is connected via the motor to the second stage inlet of the compressor. e) Liquid refrigerant levels in each chamber are controlled by a float operated valve in the evaporator. ---------CORRECT ANSWER----------------
- A Which of the following is a result of an economiser on the refrigeration system? a) an intercooling effect on the compressor b) reduction of the power required for compression in the second stage compressor c) reduction of flash vapour in the evaporator
d) increase in the refrigerating capacity of a system e) all of the above ---------CORRECT ANSWER-----------------E In actual systems there will be a gradual pressure drop through each side of the system due to a) the economiser b) friction in the evaporator, condenser, and piping c) decomposition of refrigerants d) coefficients of expansion of system components e) superheating effects Refrigeration Compressors ---------CORRECT ANSWER-----------------B Which of the following is not a function of the compressor in a refrigeration system? a) draw low pressure refrigerant out of the evaporator b) draw low temperature refrigerant out of the evaporator c) lower the temperature of the refrigerant d) maintain sufficiently low pressure in the evaporator e) raise the pressure of the refrigerant ---------CORRECT ANSWER-----------------C Which of the following is the compressor responsible for
d) None of the above e) All of the above ---------CORRECT ANSWER-----------------A One negative factor of Hermetic type reciprocating compressors is a) the compressor and motor are mounted within the same housing b) the motor is cooled by the low pressure, low temperature vapour being drawn into the housing c) it does not have or require shaft sealing d) field servicing is not possible e) the compressor is driven by an electric motor ---------CORRECT ANSWER----------- ------D In a rotating vane design rotary compressor, a good seal is maintained between the vanes and the cylinder by a) centrifugal force b) the oil c) high pressure refrigerant vapour d) low pressure suction e) the eccentric rotor size ---------CORRECT ANSWER-----------------A
For a Helical Rotor Design rotary compressor which of the following statements is true? a) The compressor consists of 3 opposing grooved rotors. b) The driving rotor has less helical lobes than the driven rotor has flute. c) The vapour is drawn in via the closed space between the driving rotor and the casing. d) The cylinders around the rotor screws must be considerably larger in diameter than the screws. e) All of the above ---------CORRECT ANSWER-----------------B Piston displacement is defined as a) the distance along which the piston travels b) the cylinder bore c) the volume of refrigerant that can be circulated through all the cylinders per unit time d) piston stroke length e) the revolutions per minute of the compressor motor ---------CORRECT ANSWER- ----------------C Refrigerant compressors a) must have inter-coolers b) could be a centrifugal type
a) roof tops b) closed rooms with low air circulation c) warm dry rooms d) cold rooms with low air circulation e) any of the above ---------CORRECT ANSWER-----------------A Which of the following statements about double tube condensers is true? a) It consists of two separate tubes side by side. b) It cannot be used with air cooled condensers. c) Water flow in the inner tube is in the opposite direction of the flow of refrigerant. d) It has the highest efficiency of the water-cooled condensers. e) It is a small condenser for a large capacity system. ---------CORRECT ANSWER----- ------------C The condenser which is very expensive to clean and requires the tubes to be cleaned with acid and neutralized is the a) shell and tube condenser b) shell and coil condenser c) double tube condenser d) evaporative condensers
e) baffle condensers ---------CORRECT ANSWER-----------------B The amount of water used in an evaporative condenser is only a small percentage of that used in a water condenser of the same capacity. This is due primarily to what? a) Evaporating condensers also use air to cool the refrigerant. b) The evaporating condensers spray refrigerated water onto condensing coil. c) Water evaporating requires a large amount of latent heat. d) Water being recirculated. e) None of the above. ---------CORRECT ANSWER-----------------C The common types of water-cooled condensers used in refrigeration systems are:
- the shell and tube
- the shell and coil
- the double tube
- the plate surface a) 1, 2, 3 b) 1, 3, 4 c) 2, 3, 4
sensing bulb by means of a small capillary tube is a/an a) thermostatic expansion valve b) automatic expansion valve c) low pressure float valve d) hand operated expansion valve e) high pressure float valve ---------CORRECT ANSWER-----------------A Which of the statements about automatic expansion valves is false? a) The valve maintains constant pressure in the evaporator during compressor operation regardless of the load. b) When the compressor stops the valve automatically shuts off. c) A spring exerting a downward force on the diaphragm tends to open the valve. d) The spring force is countered by evaporator pressure acting downward against the diaphragm which closes the valve. e) The control may be used with multiple cooling coils connected to the same compressor. ---------CORRECT ANSWER-----------------E Which control is used to maintain a constant level of liquid refrigerant in a flooded evaporator in the liquid reserve
tank? a) thermostatic expansion valve b) automatic expansion valve c) low pressure float valve d) hand operated expansion valve e) high pressure float valve ---------CORRECT ANSWER-----------------C The simple control which restricts the flow of liquid from the condenser to the evaporator and maintains a pressure difference between the two units by using a considerable pressure drop resulting from resistance between the devices length and small bore is called a) a high pressure float valve b) a low pressure float valve c) a bypass line d) a capillary tube e) an external float chamber ---------CORRECT ANSWER-----------------D In a system controlled by a high pressure float valve insufficient liquid will cause which of the following results? a) automatic system shut down
c) Divided multipart evaporators which have refrigerant control valves which can be shut off independently as the load decreases. d) Switching gears in the compressor. e) Decreasing suction in the compressor. ---------CORRECT ANSWER-----------------C Which of the following statements about evaporator dampers is true? a) These dampers decrease the resistance to the passage of air. b) When the damper is closed the quantity of air passing over the evaporator coils is at a maximum. c) Depending on the damper position the quantity of air passing through the duct varies widely. d) Multispeed blowers cannot be used in combination with evaporator dampers. e) None of the above. ---------CORRECT ANSWER-----------------E In a warm air heating system the cold air return registers are located a) in exterior walls b) in interior locations
c) under windows d) in floors e) in ceilings ---------CORRECT ANSWER-----------------B The major disadvantage of an electric resistance coil furnace for warm air heating is a) the high cost of electricity b) the danger from electric shock c) the high cost of maintenance d) the large size of the furnace e) the location of electrical wiring ---------CORRECT ANSWER-----------------A Lowboy furnaces are just over a) 1.0 m in height b) 0.8 m in height c) 1.4 m in height d) 1.6 m in height e) 1.2 m in height ---------CORRECT ANSWER-----------------E The advantage of having duct furnaces instead of a large central furnace is
A type of directly fired space heater is a) a unit heater b) a floor furnace c) a wall furnace d) all of the above e) none of the above ---------CORRECT ANSWER-----------------D High efficiency furnaces and heaters range in annual fuel utilization efficiency (AFUE) from a) 94 - 98% b) 80 - 95% c) 70 - 75% d) 60 - 70% e) 50 - 60% ---------CORRECT ANSWER-----------------B In high efficiency furnaces if the temperature of the flue gas drops below 65 degrees C the a) flue gas will condense b) water vapour will condense c) furnace burner will shut down d) furnace burner will start up e) furnace vent will close ---------CORRECT ANSWER-----------------B
In a pulse combination furnace the stated efficiency is a) 94 - 98% b) 80 - 95% c) 70 - 75% d) 60 - 70% e) 50 - 60% Warm Air Furnace Components and Maintenance ---------CORRECT ANSWER-------- ---------A Heat exchangers in gas fired furnaces are made of a) brass b) copper c) aluminum d) steel e) cast iron ---------CORRECT ANSWER-----------------D Air filters can be divided into two groups a) mechanical and rotating drum b) electronic and steam c) dry and wet d) steam and rotating drum
c) a ceiling diffuser d) a perforated panel e) all of the above ---------CORRECT ANSWER-----------------E Supply outlets should always be located a) in walls b) in floors c) in ceilings d) to best prevent cold drafts e) in baseboards ---------CORRECT ANSWER-----------------D In a warm air heating system, the heated air should enter the rooms preferably via the a) high wall registers on the inside wall b) baseboard registers on the inside wall c) baseboard registers on the outside wall d) high wall registers on the outside wall e) unit heaters on the outside wall ---------CORRECT ANSWER-----------------C Sleeve bearings on furnace fans require a) no lubrication
b) grease every six months c) a few drops of oil every six months d) a few drops of oil monthly e) flood lubrication - --------CORRECT ANSWER-----------------C Furnace heat exchangers should be checked for corrosion because a) carbon monoxide could leak into the building b) the holes reduce the furnace efficiency c) cold air could leak into the building d) too much air would enter the furnace e) the air will become too dry for comfortable heating ---------CORRECT ANSWER--- --------------A Insufficient heat throughout a building is likely caused by a) too high an air flow b) insufficient heat input c) poorly insulated ducting d) a missing filter e) poor humidity control ---------CORRECT ANSWER-----------------B Rooms that are stuffy and dry are created by
