Refrigeration Machine Operator
Course Exam with Accurate Solutions
12,000 BTUs (hour)/ 60 (minutes per hour) - ANSWER-200 BTUs minute
144 BTUs - ANSWER-must be removed from one lb of water (at 32F) to form one lb of
ice.
2000 lbs x 144 btu/lbs - ANSWER-288,000 BTUs
288,000 BTUs (day) /24 hrs (day) - ANSWER-12,000 BTUs hr
29.92 - ANSWER-The earth's pressure at sea level.
29.92 converted to "pounds per square inch" - ANSWER-14.7 psi
3 Types of refrigerant service valves - ANSWER-1. Suction service valves. 2. Discharge
Service Valve. 3. liquid line service valve or king valve (located after the condenser or
receiver)
A minimum of power should be required to compress it. - ANSWER-Different
refrigerants require different amounts of power to compress them. The less the power
required, the cheaper the operating costs of the refrigeration plant.
A one foot column of water will exert a pressure of - ANSWER-0.433 psi
Absolute Humidity - ANSWER-Absolute Humidity is the actual weight of water vapor in
a given amount of air, usually measured in grains of moisture per pound or grains per
cubic foot (a grain is 1/7000 of a pound).
Adjustable Stem - ANSWER-By turning the stem an operator determines whether there
will be a refrigerant flow between the suction line and the compressor, or between the
gauge port and the compressor.
Advantages of Dry Expansion Chiller - ANSWER-Capacity can be controlled efficiently.
As the cooling load increases, additional refrigeration circuits are brought on line. As the
load decreases, the shutting down of a compressor has a considerable affect on the
amount of energy being consumed.
Advantages to pumps in parallel - ANSWER-Two small pumps are less costly than one
large pump. A back up pump is usually necessary. Parallel pumps help to satisfy the
changing flow demands.
,Air Conditioning is a two fold process - ANSWER-As air circulates across a dx coil, both
heat and moisture are to be removed. The efficient transfer of heat requires that the
temperature of the coil be well below the temperature of the substance which is being
cooled. It should also be well below the "dew point" temperature. This will allow
moisture to condense on the coil, causing a dehumidifying effect.
Air Cooled condenser fan not supplying enough air - ANSWER-Fan should be checked
for 1. malfunction motor 2. broken belt
Air Cooled Condensers - ANSWER-Outside air is circulated across a finned or bare coil.
heat is rejected to the outside air.
Ammonia - ANSWER-R-717, Boiling point -28F, .5 lbs/min ton, Color Code Silver or
Aluminum, Toxic, non-flammable, Sharp odor, detection method - Nessler's solution,
Red Litmus paper, cannot be used with Copper or copper alloys.
ANSI/ASHRAE 34 - ANSWER-1 Purpose - This standard is intended to establish a
simple means of referring to common refrigerants instead of using the chemical name,
formula, or trade name. It also establishes a uniform system for assigning reference
numbers and safety classifications to refrigerants.
ANSI/ASHRAE 34 - ANSWER-2 Scope - This standard provides an unambiguous
system for numbering refrigerants and assigning composition-designating prefixes for
refrigerants. Safety classifications based on toxicity and flammability data are included.
ANSI/ASHRAE 34 - ANSWER-Designation and Safety Classification of Refrigerants.
ASHRAE - ANSWER-American Society of Heating, Refrigeration and Air-Conditioning
Engineers is an international membership organization founded to advance the arts and
sciences of heating, ventilation, air conditioning, refrigeration and related issues.
ASHRAE Refrigeration Code - High Flammability - ANSWER-A3, B3
ASHRAE Refrigeration Code - High Toxicity - ANSWER-B1, B2, B3
ASHRAE Refrigeration Code - Low Flammability - ANSWER-A2, B2
ASHRAE Refrigeration Code - Low Toxicity - ANSWER-A1, A2, A3
ASHRAE Refrigeration Code - No Flammability - ANSWER-A1, B1
Automatic Expansion Valve - ANSWER-Also known as a constant pressure valve, the
automatic expansion valve is designed to operate in a small to midsize refrigeration
systems that are subject to a constant load. An adjustment screw at the top of the valve
body allows the user to preset the desired evaporator pressure/temperature. Adjusting
,the spring will determine the amount of refrigerant that will be delivered to the
evaporator.
Automatic Purger - ANSWER-1. Non Condensables and refrigerant vapor travel into the
purge drum. The purge drum contains the cooling coil of a self contained refrigeration
system. The refrigerant is condensed, separating it from the non-condensables. 2. Low
pressure liquid refrigerant exits the purge drum, returning to the low side of the system.
3. A pump out compressor removes the condensables from the purge drum through a
relief line which vents to the atmosphere. The pump out compressor is activated when
the pressure in the purge drum is low enough to ensure separation of refrigerant and
non-condensables.
Auxiliary Components - ANSWER-Auxiliary Components are designed to either
enhance or protect the system. It is possible to remove an auxiliary component from a
system without affecting its ability to produce cooling.
Ball Valve - ANSWER-Named for the ball shaped disc in the body.
A hole through the ball center provided straight through flow.
Can be opened or closed in a quarter turn of the handle.
Has flow pattern of gate valves and tight shut off characteristics of globe valves.
Light and durable.
Barometer - ANSWER-A device for predicting weather changes.
Barometric Pressure to Psia - ANSWER-Psia - = Hg x .491
Belt Driven - ANSWER-The compressor is connected to the motor by one or a series of
pulleys and belts.
Benefits of indirect systems - ANSWER-1. Segregating the refrigeration system protects
the building's occupants from hazards caused by refrigeration leaks and fire. 2. Hold
Over Capacity.
Benefits of Sub Cooling - ANSWER-Prevents inadvertent vaporization as it travels
through the liquid line. Another benefit is an associated increase in cooling capacity at
the evaporator.
Biological Growth Control - ANSWER-Biological growth (algae, bacteria, fungi) can
affect cooling equipment operation but more importantly pose health risk. Legionnaires
Disease comes from the bacteria Legionella pneumolphia and will survive in warm moist
environments. Microbiocides are used to control biological growth and fall into two
categories and are regulated by the EPA. Oxidizing micro biocides are the most
effective treatment including chlorine, bromine, ozone, iodine. Non Oxidizing micro
biocides including Isothiazolones, Benzotriazole, proprietary blends.
, Blow down Valve - ANSWER-The blow down valve is located downstream of the
exchanger. Blowing down the highest temperature water will add to the efficiency of the
system. Chemical feed must be installed downstream of the blow down valve to avoid
wasting chemicals.
Boiling Point - ANSWER-A refrigerant with a low boiling point can achieve low
evaporator temperature without having to be in a vacuum.
Brines - ANSWER-Brines are secondary refrigerants that circulate in the closed piping
system that routes through the tube side of the system's evaporator. In indirect
refrigeration systems the evaporator are commonly referred to as chillers or brine
coolers.
BTU "British Thermal Unit" - ANSWER-A BTU is the quantity of heat needed to raise
one pound of water one degree Fahrenheit.
Bubbles in the sight glass - ANSWER-Bubbles in the sight-glass can also be the
product of pressure drop in the liquid line or across the filter dryer, however these
circumstances occur less frequently. Students should assume that bubbles in the sight
glass are caused by "loss of the liquid seal"
Calcium Chloride (CaCl) - ANSWER-Eutectic Point -59F, Specific Gravity 1.29, Sodium
Dichromate (Rust Inhibitor) lbs per 1000 cu/ft of brine 100
Capillary tube metering device - ANSWER-Capillary tube metering devices are used in
small refrigeration systems; ie window units and compact refrigerators. As the name
implies, they consist of small diameter length of tube that connects the leaving side of
the condenser with the evaporator inlet.
Carbon Dioxide - ANSWER-R-744, Discharge Pressure @86F - 1031psig, Critical Temp
87.8F, silver color code, Non-toxic, Non-flammable, colorless, odorless, Detection
method - Soapy water, Bromothymol Blue
Categories of filter dryers - ANSWER-There are two major categories of filter dryers,
"sealed type" and "replaceable core". In either case the work performed by the dryer is
made possible by the material inside of the drier which is referred to as a desiccant.
Centrifugal Compressor Lubrication - ANSWER-The compressor bearings are lubed by
a force feed system. Pressurized oil is fed to the bearings by a motor driven oil pump
which is submerged in the oil sump. Bearing oil pressure is controlled by a regulating
valve in the oil pump discharge. The bearing oil pressure is monitored by an oil pressure
control which senses the pressure difference across the bearings. The purpose of this
control is to prevent compressor start up until oil pressure is developed and to prevent
continued operation should the oil pressure fall below design limits. Oil temperature is
maintained at approximately 15F within the sump by a thermostatically controlled
electric heater. The 150F temp is required to prevent refrigerant from condensing in the
Course Exam with Accurate Solutions
12,000 BTUs (hour)/ 60 (minutes per hour) - ANSWER-200 BTUs minute
144 BTUs - ANSWER-must be removed from one lb of water (at 32F) to form one lb of
ice.
2000 lbs x 144 btu/lbs - ANSWER-288,000 BTUs
288,000 BTUs (day) /24 hrs (day) - ANSWER-12,000 BTUs hr
29.92 - ANSWER-The earth's pressure at sea level.
29.92 converted to "pounds per square inch" - ANSWER-14.7 psi
3 Types of refrigerant service valves - ANSWER-1. Suction service valves. 2. Discharge
Service Valve. 3. liquid line service valve or king valve (located after the condenser or
receiver)
A minimum of power should be required to compress it. - ANSWER-Different
refrigerants require different amounts of power to compress them. The less the power
required, the cheaper the operating costs of the refrigeration plant.
A one foot column of water will exert a pressure of - ANSWER-0.433 psi
Absolute Humidity - ANSWER-Absolute Humidity is the actual weight of water vapor in
a given amount of air, usually measured in grains of moisture per pound or grains per
cubic foot (a grain is 1/7000 of a pound).
Adjustable Stem - ANSWER-By turning the stem an operator determines whether there
will be a refrigerant flow between the suction line and the compressor, or between the
gauge port and the compressor.
Advantages of Dry Expansion Chiller - ANSWER-Capacity can be controlled efficiently.
As the cooling load increases, additional refrigeration circuits are brought on line. As the
load decreases, the shutting down of a compressor has a considerable affect on the
amount of energy being consumed.
Advantages to pumps in parallel - ANSWER-Two small pumps are less costly than one
large pump. A back up pump is usually necessary. Parallel pumps help to satisfy the
changing flow demands.
,Air Conditioning is a two fold process - ANSWER-As air circulates across a dx coil, both
heat and moisture are to be removed. The efficient transfer of heat requires that the
temperature of the coil be well below the temperature of the substance which is being
cooled. It should also be well below the "dew point" temperature. This will allow
moisture to condense on the coil, causing a dehumidifying effect.
Air Cooled condenser fan not supplying enough air - ANSWER-Fan should be checked
for 1. malfunction motor 2. broken belt
Air Cooled Condensers - ANSWER-Outside air is circulated across a finned or bare coil.
heat is rejected to the outside air.
Ammonia - ANSWER-R-717, Boiling point -28F, .5 lbs/min ton, Color Code Silver or
Aluminum, Toxic, non-flammable, Sharp odor, detection method - Nessler's solution,
Red Litmus paper, cannot be used with Copper or copper alloys.
ANSI/ASHRAE 34 - ANSWER-1 Purpose - This standard is intended to establish a
simple means of referring to common refrigerants instead of using the chemical name,
formula, or trade name. It also establishes a uniform system for assigning reference
numbers and safety classifications to refrigerants.
ANSI/ASHRAE 34 - ANSWER-2 Scope - This standard provides an unambiguous
system for numbering refrigerants and assigning composition-designating prefixes for
refrigerants. Safety classifications based on toxicity and flammability data are included.
ANSI/ASHRAE 34 - ANSWER-Designation and Safety Classification of Refrigerants.
ASHRAE - ANSWER-American Society of Heating, Refrigeration and Air-Conditioning
Engineers is an international membership organization founded to advance the arts and
sciences of heating, ventilation, air conditioning, refrigeration and related issues.
ASHRAE Refrigeration Code - High Flammability - ANSWER-A3, B3
ASHRAE Refrigeration Code - High Toxicity - ANSWER-B1, B2, B3
ASHRAE Refrigeration Code - Low Flammability - ANSWER-A2, B2
ASHRAE Refrigeration Code - Low Toxicity - ANSWER-A1, A2, A3
ASHRAE Refrigeration Code - No Flammability - ANSWER-A1, B1
Automatic Expansion Valve - ANSWER-Also known as a constant pressure valve, the
automatic expansion valve is designed to operate in a small to midsize refrigeration
systems that are subject to a constant load. An adjustment screw at the top of the valve
body allows the user to preset the desired evaporator pressure/temperature. Adjusting
,the spring will determine the amount of refrigerant that will be delivered to the
evaporator.
Automatic Purger - ANSWER-1. Non Condensables and refrigerant vapor travel into the
purge drum. The purge drum contains the cooling coil of a self contained refrigeration
system. The refrigerant is condensed, separating it from the non-condensables. 2. Low
pressure liquid refrigerant exits the purge drum, returning to the low side of the system.
3. A pump out compressor removes the condensables from the purge drum through a
relief line which vents to the atmosphere. The pump out compressor is activated when
the pressure in the purge drum is low enough to ensure separation of refrigerant and
non-condensables.
Auxiliary Components - ANSWER-Auxiliary Components are designed to either
enhance or protect the system. It is possible to remove an auxiliary component from a
system without affecting its ability to produce cooling.
Ball Valve - ANSWER-Named for the ball shaped disc in the body.
A hole through the ball center provided straight through flow.
Can be opened or closed in a quarter turn of the handle.
Has flow pattern of gate valves and tight shut off characteristics of globe valves.
Light and durable.
Barometer - ANSWER-A device for predicting weather changes.
Barometric Pressure to Psia - ANSWER-Psia - = Hg x .491
Belt Driven - ANSWER-The compressor is connected to the motor by one or a series of
pulleys and belts.
Benefits of indirect systems - ANSWER-1. Segregating the refrigeration system protects
the building's occupants from hazards caused by refrigeration leaks and fire. 2. Hold
Over Capacity.
Benefits of Sub Cooling - ANSWER-Prevents inadvertent vaporization as it travels
through the liquid line. Another benefit is an associated increase in cooling capacity at
the evaporator.
Biological Growth Control - ANSWER-Biological growth (algae, bacteria, fungi) can
affect cooling equipment operation but more importantly pose health risk. Legionnaires
Disease comes from the bacteria Legionella pneumolphia and will survive in warm moist
environments. Microbiocides are used to control biological growth and fall into two
categories and are regulated by the EPA. Oxidizing micro biocides are the most
effective treatment including chlorine, bromine, ozone, iodine. Non Oxidizing micro
biocides including Isothiazolones, Benzotriazole, proprietary blends.
, Blow down Valve - ANSWER-The blow down valve is located downstream of the
exchanger. Blowing down the highest temperature water will add to the efficiency of the
system. Chemical feed must be installed downstream of the blow down valve to avoid
wasting chemicals.
Boiling Point - ANSWER-A refrigerant with a low boiling point can achieve low
evaporator temperature without having to be in a vacuum.
Brines - ANSWER-Brines are secondary refrigerants that circulate in the closed piping
system that routes through the tube side of the system's evaporator. In indirect
refrigeration systems the evaporator are commonly referred to as chillers or brine
coolers.
BTU "British Thermal Unit" - ANSWER-A BTU is the quantity of heat needed to raise
one pound of water one degree Fahrenheit.
Bubbles in the sight glass - ANSWER-Bubbles in the sight-glass can also be the
product of pressure drop in the liquid line or across the filter dryer, however these
circumstances occur less frequently. Students should assume that bubbles in the sight
glass are caused by "loss of the liquid seal"
Calcium Chloride (CaCl) - ANSWER-Eutectic Point -59F, Specific Gravity 1.29, Sodium
Dichromate (Rust Inhibitor) lbs per 1000 cu/ft of brine 100
Capillary tube metering device - ANSWER-Capillary tube metering devices are used in
small refrigeration systems; ie window units and compact refrigerators. As the name
implies, they consist of small diameter length of tube that connects the leaving side of
the condenser with the evaporator inlet.
Carbon Dioxide - ANSWER-R-744, Discharge Pressure @86F - 1031psig, Critical Temp
87.8F, silver color code, Non-toxic, Non-flammable, colorless, odorless, Detection
method - Soapy water, Bromothymol Blue
Categories of filter dryers - ANSWER-There are two major categories of filter dryers,
"sealed type" and "replaceable core". In either case the work performed by the dryer is
made possible by the material inside of the drier which is referred to as a desiccant.
Centrifugal Compressor Lubrication - ANSWER-The compressor bearings are lubed by
a force feed system. Pressurized oil is fed to the bearings by a motor driven oil pump
which is submerged in the oil sump. Bearing oil pressure is controlled by a regulating
valve in the oil pump discharge. The bearing oil pressure is monitored by an oil pressure
control which senses the pressure difference across the bearings. The purpose of this
control is to prevent compressor start up until oil pressure is developed and to prevent
continued operation should the oil pressure fall below design limits. Oil temperature is
maintained at approximately 15F within the sump by a thermostatically controlled
electric heater. The 150F temp is required to prevent refrigerant from condensing in the
