Mohawk Basic AC and Refrigeration Practice Exam

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• Approximately how much air is required per ton by an air cooled condenser?
• A single phase motor in which the capacitor remains connected when the motor runs is called?
• Which type of vapor is typically used in refrigeration systems to carry away heat?
• What happens during the phase change of refrigerant from liquid to vapor?
• In a refrigeration system, what is the standard operating pressure for low side valves?
• What is the boiling point of ammonia at atmospheric pressure?
• Why is the presence of oil often the first indication of a refrigerant leak in a system?
• In an AC circuit, which properties must you multiply to calculate wattage?
• What year will HCFC refrigerants be phased out in Ontario?
• What component helps in measuring the pressure of refrigerants in a system?
• What is an important function of the compressor in a refrigeration system?
• Which component is primarily responsible for controlling the flow of refrigerant in the system?
• In refrigeration, what role does a condenser typically play?
• How should refrigerant piping typically be installed?
• Which type of motor does not require a starting switch or mechanism?
• What condition describes a sight glass in a full liquid line?
• When removing the gauge port plug from the compressor discharge service valve, what position should the valve be in?
• When does the suction valve on a reciprocating compressor open?
• Secondary refrigerants are usually?
• Compressor capacity reduction devices are designed to reduce capacity based on what?
• What effect does a failing capacitor have on a single-phase motor?
• What happens if the suction saturation temperature (SST) decreases from 42F to 34F?
• What types of heat does a cooling system remove?
• Why is it important to not exceed the maximum fill percentage when transferring refrigerants?
• When installing isolation valves, what should the isolation section of the system be protected against?
• What is the purpose of insulating the oil separator in a refrigeration system?
• Corrosion tendencies of oil are an indication of what?
• What is the function of an oil pressure safety control?
• What is the main process involved in refrigeration?
• Which of the following refrigerants cause the least amount of harm to stratospheric ozone?
• What happens to the resistance if the voltage of a device increases while the current remains constant?
• What type of refrigerant cycle is most commonly used in air conditioning?
• To prevent refrigerant floodback, the minimum superheat at the compressor inlet should be maintained at?
• When testing a capacitor, what indicates that the capacitor is probably in good condition?
• What is the primary function of a suction accumulator in a refrigeration system?
• How do you change the direction of rotation of a capacitor start motor?
• In determining compressor displacement, which factor is not considered?
• What is the primary purpose of a filter drier in refrigeration?
• What is the first step in troubleshooting a refrigeration system?
• What must the temperature of the medium being cooled be in relation to the evaporator temperature?
• What is the purpose of the external equalizer line used with a thermostatic expansion valve?
• What role does the capacitor play in a single-phase motor circuit?
• What is the Rankine scale value for absolute zero?
• What is the natural direction of heat transfer?
• What is the equivalent of one ton of refrigeration in British thermal units (BTUs)?
• What is the resistance found in good, usually closed relay contacts?
• Which type of oil is suitable for a refrigeration system using HFC refrigerant?
• What controls the opening and closing of all refrigeration compressor suction and discharge service valves?
• A crankcase pressure regulating valve functions as what type of valve?
• A lamp has a source voltage of 110 volts and a current of 0.9 amps. What is the resistance of the lamp?
• What type of refrigerant flow is maintained in a functioning refrigeration system?
• How are cylinders used for returning used refrigerant to suppliers marked?
• What unit is commonly used to express the effectiveness of air conditioning systems?
• What is a characteristic feature of a suction accumulator?
• The thermostatic expansion valve is primarily controlled by which factor?
• What is the mechanism through which heat travels in a heated iron bar?
• In a situation with a condensing unit controlled by a low pressure control in an unheated basement, what affects the temperature of an attached fixture in a warmer location?
• What separates the high and low side of the refrigeration system in operation?
• When using a thermostatic expansion valve, why is it important that the power head does not become colder than the bulb?
• In a single-phase motor, what is the relationship between the starting winding and the run winding?
• What action is taken to decrease the superheat setting of a Thermostatic Expansion Valve (TEV)?
• What component is used to control the flow of refrigerant in a system?
• What is the total capacitance of two 100 uF capacitors connected in series?
• A system with low head pressure and high back pressure is likely experiencing which issue?
• Why is it essential to use a recovery machine when collecting refrigerant?
• Which factors affect the resistance of a wire?
• Which of the following is considered a thermodynamic property of a refrigerant?
• How can a cycle be defined in electrical terms?
• What could an undercharged refrigeration system be easily mistaken for?
• An overcharge of oil in a system with capillary feed will likely cause which of the following?
• Which component is crucial for efficiency in a refrigeration cycle involving expansion valves?
• According to Ohm's Law, what is the relationship between current and voltage in a simple circuit?
• What is the synchronous speed of a four pole motor compared to a two pole motor?
• Low temperature silver alloy brazing material has flow points normally ranging between?
• Locked rotor current is generally how many times greater than the run current?
• How does increasing pressure affect the boiling point of a liquid?
• What can cause a compressor to shut down unexpectedly?
• What effect does high humidity have on a refrigerant system's efficiency?
• Why is abnormally low suction pressure undesirable?
• In what way can liquid refrigerant be charged into the system?
• What is the main consequence of a sticky expansion valve?
• What principle does the operation of a potential relay rely on?
• Refrigerant leaves the expansion valve as?
• How is sensible heat defined in refrigeration practice?
• What is the primary purpose of a pressure limiting thermostatic expansion valve?
• Why is a single-phase motor not self-starting?
• What is the chemical formula for R22?
• According to the B-52 mechanical code, to what percentage should liquid receivers be filled during pumpdown at 32 degrees Celsius?
• What happens to the boiling point of a refrigerant as system pressure increases?
• What does an increase in molecular weight of refrigerant compared to oil lead to?
• What is the ideal temperature for a refrigerator's evaporator coil?
• Which factor is critical for the lubrication in a refrigerant system?
• When adding refrigerant from a service cylinder through the suction service valve, how must the cylinder be positioned?
• When measuring superheat, where is one of the readings taken?
• What aspect of an air conditioning system can be negatively affected if there is too much refrigerant?
• Why is a suction accumulator recommended downstream of a low temperature coil?
• If a refrigerant system with an air-cooled condenser cycles off in cold weather, what issue may prevent the compressor from restarting?
• How should injuries caused by contact with liquid refrigerant be treated?
• When a hermetic compressor "burns out", what is the main cause of contaminates forming?
• How many gauges are typically found on a refrigerant gauge and testing manifold?
• What is typically found in a closed loop heating system?
• What is the normal position of starting relay contacts in a system?
• Which of the following metals is known to be the best conductor of electricity?
• What type of refrigerant is commonly used in most household refrigerators?
• How often must refillable refrigerant cylinders be retested?
• Using absolute pressure, if the pressure is 14.7 lbs, what is the gauge pressure?
• The symbol Hz represents a unit of what?
• What is the purpose of sizing suction lines in refrigeration systems?
• What does the fundamental rule of static electricity state?
• When heat is added to a system being dehydrated by evacuation?
• Where would you find a ring coupling connecting rod?
• Which device is primarily used to measure atmospheric pressure?
• What happens to the vapor pressure of a liquid when its temperature increases?
• In refrigeration systems, what is primarily the purpose of the condenser?
• How does an increase in humidity affect the dry bulb temperature?
• What is the specific heat of a material?
• When the temperature of a refrigerant vapor is decreased, what happens to its density?
• What process describes cleaning refrigerant for reuse through distillation and filtering?
• You find a "blown" start capacitor marked 330 volts - 140 uF. Which set of capacitors on your truck can be used as a replacement?
• What happens to the refrigerant in the evaporator?
• What is the typical temperature change for sizing suction lines?
• What is the normal procedure for checking electrical circuits?
• Why must suction filters be sized correctly?
• How is thermal conductivity influenced in materials?
• What is the primary function of a compressor in a refrigeration cycle?
• What is a common sign of refrigerant leakage in a system?
• What is the recommended maximum fill percentage for a cylinder when transferring refrigerant?
• Which pressures and temperatures are used when applying gas laws?
• Under what condition do the wet bulb temperature and dry bulb temperature become the same?
• What effect does clearance volume in a compressor have?
• Which of the following is not considered a desirable characteristic of a good refrigerant?
• What is the purpose of a high-pressure cutout in a refrigeration system?
• Refrigerant piping condensation issues typically arise when the dew point of the surrounding air is in relation to the pipe temperature?
• At what temperature does R-12 refrigerant boil?
• In a refrigeration system, what is the purpose of a compressor?
• What unit is used to measure electrical power?
• How can ambient temperature be defined?
• Which of the following practices is essential for maintaining efficient compressor operation?
• If a fan motor runs at 1800 RPM with a 3 inch pulley and drives a fan with a 9 inch pulley, what is the fan speed?
• In a vapor compression cycle, the heat absorbed in the evaporator must equal what?
• In a refrigeration cycle, the evaporator absorbs heat at what point?
• What is the primary purpose of a compressor in refrigeration?
• Where are refrigeration service valves typically located?
• What does the temperature differential in thermostats refer to?
• What is the primary purpose of a heat exchanger in refrigeration systems?
• When cleaning a shell and coil condenser, what method is commonly recommended?
• What type of contacts does a current relay have?
• What is the effect of incorrect refrigerant charge on system performance?
• What is the method for changing the direction of rotation in a three-phase motor?
• What is the primary function of the condenser in a refrigeration system?
• In electrical circuits, the time rate of doing work is expressed in?
• Air in a refrigeration system results in?
• What does the presence of excessive pressure indicate when working with isolation valves?
• What are the basic voltages that can be taken off of a 4 wire 208 volt system?
• What could result if an evaporator is not properly maintained?
• Which of the following conditions can lead to frost formation on evaporator coils?
• On externally equalized valves, where is the external connection typically made?
• At what temperature does oil breakdown begin to occur?
• What does a higher capacitance rating indicate about a capacitor's performance?
• If a condensing unit short cycles, and is not low on refrigerant with a hissing sound in the expansion valve and a cold liquid line, what is the likely cause of the trouble?
• How should safety controls be wired in a circuit that includes operating controls?
• Evaporator TD refers to the temperature difference between which two points?
• What potential issue can "foaming" in a compressor crankcase cause?
• Which type of air conditioning system removes humidity as a key part of its function?
• What type of gauge is used to measure pressure above and below atmosphere?
• What is the primary voltage and amperage if the secondary voltage of a transformer is 24 volts and 20 amps with a turns ratio of 5:1?
• The control of the low side of the float in a refrigeration system is determined by what?
• In a series circuit, what is true about the total current?
• What is the effect of using nitrogen in the piping during a brazing operation?
• The compression ratio under which a refrigeration compressor operates is?
• What is a characteristic of a split phase motor?
• What happens to refrigerant flow when pressure across the capillary tube increases?
• What does a molecule of ozone consist of?
• What is illegal to import, manufacture or sell in containers of refrigerant containing less than?
• How does the SSU (Saybolt Seconds Universal) number relate to the viscosity of a refrigerant oil?
• How can system pressure be adjusted manually in refrigeration systems?
• A pound of water vapor contains approximately how many grains?
• What method should be used to join copper to steel?
• What is the general CFM of air required through the evaporator for each ton of air conditioning?
• Where should an oil separator be installed in a refrigeration system?
• What is generally the main function of a thermostatic expansion valve?
• Why is it important to insulate the suction line in refrigeration systems?
• Which component in a refrigerator absorbs heat from inside the appliance?
• What is a micron?
• Latent heat refers to heat that is required to achieve what condition?
• What is the size of the largest electrical conductor?
• What are the three operating pressures of the thermostatic expansion valve?
• What are devices that use water columns for measuring small pressure changes called?
• What could prolonged low pressure conditions lead to in a refrigeration unit?
• Where are static or natural condensers most frequently found?
• What is the primary purpose of a crankcase heater on a motor compressor?
• How much heat must be removed to cool 1000 lbs of water from 72 degrees F to -18 degrees F?
• What is a common sign of a refrigerant leak?
• Which device is used to regulate refrigerant flow in a refrigeration system?
• How is the viscosity of an oil defined?
• What effect does increasing the thickness of a compressor valve plate gasket have on compressor capacity?
• What happens to the viscosity of a mixture as the percentage of R12 in oil increases?
• What chemical, other than chlorine, has been shown to cause damage to the ozone layer?
• An evaporator pressure regulator is designed to maintain which of the following?