Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula S O 2.It is a toxic gas responsible for the smell of burnt matches.It is released naturally by volcanic activity and is produced as a by-product of copper extraction and the burning of fossil fuels contaminated with sulfur compounds. How many BTUs does each pound of water evaporating remove? The fins on finned tube coils increase heat transfer by: Increasing the surface area exposed to the air. What is the purpose of low ambient controls for air cooled condensers? The operating mechanism inside most refrigeration gauges is: The amount of absolute pressure remaining in the system. Optional components found on the low side of a refrigeration system include: Suction line filter, accumulator, and evaporator pressure regulator. 2 0 obj Which pressure relief device works primarily by temperature? What is the advantage of balanced port TEVs? Water cooling evaporator constructions include: Tube in tube, Shell and coil, and Shell and tube. Which of the following is the standard saturated temperature drop in the suction line? How can semihermetic compressors be characterized? High suction pressure, low superheat, and low subcooling. 8 × 1.2) + 30 lbs = 68 lbs (rounded). An advantage of open drive compressors is that: The motor and compressor can be replaced separately. Can cause poor oil return because of low refrigerant velocity. Pulp sensibility tests include thermal and electric tests, which extrapolate pulp health from sensory response. A system operating with a suction line superheat of 5° or less is probably: A common application for centrifugal compressors is: One technique for improving efficiency and comfort through compressor selection is to select: A compressor with capacity control to match the compressor capacity with the refrigeration load. Which of the following metering devices can respond to changes in system conditions? If the refrigerant is recovered improperly from a water-cooled condenser: If the refrigerant condensing saturation temperature is 100°F at the start of the process, what would the entering water temperature be? n an air conditioner with a fixed metering device, a decrease in the outdoor ambient causes: Valves that open and close rapidly under the control of electronic circuits are: An overfeeding metering device can cause? Which of the following modifications would alleviate refrigerant migration in a long-line system? New temperature/starting temperature × starting pressure. The main cause of high condensing temperature and pressure in air cooled condensers is: Subcooling the liquid refrigerant increases system efficiency by: Insuring a solid stream of liquid to the metering device. What is the primary advantage of a remote air cooled condenser on an ice machine? What is the general formula for calculating the effect of temperature on a holding charge? What advantages do orifice type metering devices have over capillary tubes? Leaks in commercial refrigeration systems must be repaired if they have an annual leak rate of: Why does a pressure drop not necessarily indicate a refrigerant leak? Why will the compressor on a leaking system become overheated? Which of the four types of refrigeration systems cools the air without removing any heat from the air? It is the cause of hepatitis (liver damage) and liver cancer. Hazards are anything that can cause harm and every place of work has them. The 0°F evaporator because of the higher pressure difference. Acts as an insulator reducing the heat transfer of the coil. Where is the suction line temperature read when adjusting a TEV? In a water-cooled condenser, what does an increase in head pressure and increase in temperature difference across the condenser indicate? When the hand wheels on the gauge manifold are turned counter clockwise: Refrigerant can flow between the outer hoses and the center hose. Optional components on the high side of a refrigeration system include: Discharge line muffler, oil separator, liquid receiver, and liquid line filter-drier. To increase the evaporator pressure, the adjustment on top of an automatic expansion valve should be: A system with a loose TEV sensing bulb would most likely: Which type of metering device used on flooded evaporators opens to admit more liquid refrigerant into the evaporator when the liquid level in the evaporator drops? They do not control flow to service ports. The total amount of heat in the refrigerant. How much would system capacity be increased by subcooling the liquid refrigerant leaving the condenser an extra 12°F? A refrigerant sensor that changes conductivity when exposed to refrigerant is: Ceramic metal oxide semi-conductor (CMOS). The suction line temperature and pressure. When connecting a recovery system for push-pull liquid recovery, the outlet of the recovery unit is connected to: The discharge service valve on the system. Find out how you can manage hazards, and keep yourself and your workers safe from harm. Why are biocides added to cooling-tower water? Three different design screw compressors are: Single screw with gate rotors, dual screw, and triple screw. A refrigerant blend with a glide of 10°F or more would be considered: The separation of the refrigerant components in a zeotropic refrigerant when the refrigerant evaporates or condenses is known as: A fluorinated refrigerant whose number starts with a 5 is: Small appliances such as household refrigerators and freezers now primarily use: Zeotropes are mixtures of two or more refrigerants: New residential air conditioning systems now primarily use: Why are liquid line filter-driers required for all systems using HFC refrigerant? The pressure drop due to vertical lift in a liquid line is approximately: An R-22 system has a 28-ft lift and a 7 psi pressure drop in the liquid line due to vertical lift. They require lower vacuums than for other types. What is the maximum safe fill level for a refillable refrigerant cylinder? We are an Open Access publisher and international conference Organizer. Flash gas in the liquid line can be identified by: A significant temperature drop in the liquid line temperature. What type of compressors contain the compressor and motor together inside a welded steel housing? Small Domestic refrigerators and freezers use: Air conditioning tube and fin coils are commonly available as: To prevent liquid slugs from leaving the evaporator and entering the compressor, direct expansion evaporators: Are typically fed at the bottom with suction gas leaving at the top. Why does oil slugging occur in a compressor? 4 0 obj Because the POE oil used with HFC refrigerant is very hygroscopic. What is the problem associated with disconnecting a gauge manifold through its middle leg? They have a bolted housing that encloses both the compressor and motor. Oil slugging is caused by a sudden return of large amounts of refrigerant oil. In a reciprocating compressor, the piston is driven up and down in the cylinder by the connecting rod and crankshaft. Its ability to maintain a very accurate temperature across the entire evaporator surface. What is the primary difference between air cooled condensers on standard efficiency systems and air cooled condensers on high efficiency systems? Oh no! A water-cooled condenser operates 15°F below an air-cooled condenser. What is the purpose of TEV sensing bulbs with a limited, or gas charge? Leaks on the low side of a Type III system are indicated by: Why has the use of halide torches in leak detection decreased in popularity? Refrigerant enters as a saturated mixture and leaves as a: The percentage of air that travels through a tube and fin coil without touching any coil surface is called the: On a commercial refrigeration system with electric defrost, what does the compressor do during the defrost cycle? For which of the following is the last part of the evaporator used? If the low side test pressure is not know, the maximum pressure that should be used for leak testing an R-22 refrigeration system with hermetic compressor is: Leaks in air conditioning systems must be repaired if they have an annual leak rate of: Which of the following is an indicator of a leaking refrigerant system? The service port is closed and the system is open to the line. Capillary tube metering devices are commonly used today in: The operation of a thermostatic expansion valve can best be described as: Bulb pressure = evaporator pressure + spring pressure. The small gaps between the screws on the screw compressor are sealed by: A compressor that uses a large off-center rotating shaft and multiple blades that follow the cylinder walls as the shaft rotates is a: Assuming they both have the same condenser temperature, which application requires more horsepower to produce a ton of cooling: a 0°F evaporator or a 40°F evaporator? Hot compressor discharge gas is routed to the evaporator. Which is the primary purpose of a split-system installation valve's service port? When calculating the effect of temperature change on a standing charge: Always use absolute pressure and temperature. One way to reduce the amount of refrigerant spray when connecting and disconnecting refrigeration hoses from Schrader valves is to: What types of system access valves do residential air conditioning systems usually have? On an R410A air conditioning system, the refrigerant leaving the ________ is 118 psig, 50°F, 100% superheated gas. Which leak detectors can be used with systems that are only charged with nitrogen? What is the maximum safe fill weight of a recovery cylinder with a tare weight of 30 pounds, a water capacity of 40 pounds, holding a refrigerant with a specific gravity of 1.2? Gas trapped in the compressor clearance space is expanded at the beginning of the suction stroke. What is the possible error for a gauge that has a 1% of full scale accuracy if the gauge reads up to 300 psig? Why might leak testing with nitrogen be preferable to using R-22? 40 lbs × 0. How does a two-step scroll compressor achieve capacity reduction? .Refrigerant characteristics shown on a pressure-enthalpy diagram include: What units are used to indicate specific enthalpy? Why is it important to measure the vacuum level on the system? To ensure the best experience, please update your browser. Cooling towers in which the water circulating in the tower is separate from the water circulating through the condenser are called: What type of water cooled condenser is easiest to clean? What is the material inside the filter-drier called? Refrigerants are the fundamental substances used to transfer heat during the mechanical cooling process. The two general categories of metering devices are: As refrigerant passes through the metering device, it: Commercial refrigeration equipment for ice cream storage typically uses: Higher than the dry coil static pressure drop. Front: clockwise, line port is closed but the middle port is open to the service port. back; counterclockwise, service port is closed but middle port is open. <> The coil size is increased to increase the heat transfer area. The primary cause of high condensing temperatures in water cooled condensers is: Fan cycling, fan speed control, damper control, and condenser flooding are different types of: A device used to evenly distribute mixtures of liquid and vapor refrigerant leaving the TEV to multiple evaporator circuits is called a: An R22 refrigeration system requires a superheat of 8°F. ;�Y7����t�ΰ:��,+�G{V@/ܚM# �u[�[2�;B�`W�P���y��QSOhw+�"�D�- �n�[�� T�Hhw뭣%��|����%$��B�5͞����c+�%,�w|%��6�a�X �j���Bh2�����X����s���;o�GA��w. Straightening on a rise in pressure and curling on a fall in pressure. Hydraulic pressures will develop and break compressor parts if: Liquid refrigerant enters the compressor cylinders. On a typical plot of the refrigeration cycle, where does liquid refrigerant first begin forming in the condenser? If the line length is 100 ft. and the system needs a capacity of 2 tons, what size line should be used? They have a welded shell which holds both the compressor and motor. To prevent the system refrigerant from quickly dropping in temperature and pressure, refrigerant recovery should: The four parts of the EPA Certification exam include: Core, Type I - small appliances, Type II - high pressure and very high pressure appliances, and Type III - low pressure appliances. The risers are sized smaller to maintain a minimum velocity to lift the oil. Commercial refrigeration systems normally have: A suction service valve, discharge service valve, and a king valve. Which pressure relief device is essentially an engineered weak point? endobj Why do some commercial buildings need air conditioning in the winter? The factors that must be considered when sizing the discharge line are: When installing a double riser in a commercial refrigeration system, which of the following statements is true? The blue gauge and hose on a gauge manifold set are used for: Reading pressures on the low side of the system. What types of system access valves do commercial refrigeration systems usually have? How much heat is rejected through condensation? 9? Which type of glove should be used if prolonged contact with liquid or gas is expected? Which of the following systems uses compression pumps and condensers to cool the air? These are called bee bread. What is the refrigeration effect of a system if the liquid entering the evaporator has an enthalpy of 60 BTU/lb and the vapor leaving the evaporator has an enthalpy of 110 BTU/lb? However, virtually all patients have chronic or recurring cough. An internal rotating plate opens and closes two drilled ports in the scroll. Which of the following is the line that drops straight down because no heat is gained or lost? It has been illegal to vent ozone depleting refrigerants from stationary equipment since: Technicians have been required to pass an EPA certification exam to handle refrigerant since: How is recovering into a receiver accomplished? Liquid refrigerant should always be recovered first from chillers: To keep from freezing the water in the chiller tubes. Where in the system is an oil separator installed? endobj Temperature of refrigerant and type of refrigerant. Refrigeration system component that absorbs heat out of the product is the: Commercial refrigeration equipment for storing viral cultures typically uses: What controls the length of the defrost cycle on most commercial refrigeration systems? Whilst pulp sensibility tests are the most commonly used in clinical practice, they are not without limitations and shortcomings. The state of the refrigerant is: Which of the two refrigerant lines going to the compressor is larger? Ground up aluminum can react violently with which of the following? A compressor that compresses gas between a fixed spiral and an orbiting spiral is a: An oil slinger is used with reciprocating compressors that are lubricated by: Which of the following is true of a medium-temperature refrigeration unit? It required that they hold a certification. We own and operate 500 peer-reviewed clinical, medical, life sciences, engineering, and management journals and hosts 3000 scholarly conferences per year in the fields of clinical, medical, pharmaceutical, life sciences, business, engineering and technology. If the evaporator saturation pressure is 43 psig, what should the bulb temperature be? Equals the heat absorbed by the evaporator plus the heat added by the compressor. The system capacity of an air conditioner with a fixed metering device: Decreases when the indoor wet bulb temperature rises. The most common hazard encountered when installing and removing refrigeration gauges is: What type of sensor is most often used to detect very low parts per million for toxic refrigerants? A flattened tube in the shape of a question mark that straightens under pressure. What happens to the evaporator fan motor when the defrost cycle is terminated? Commercial buildings often have large internal heat loads from people, lights, and machines. As the refrigerant temperature drops during the desuperheating phase of the refrigeration cycle, the refrigerant pressure: Where in the cycle does heat enter the refrigerant? stream The fan shuts off until the defrost termination thermostat senses that the evaporator is cold again. They open when they are backseat cracked and close when they are backseated. It does not work with most modern refrigerants. Why is back-seating a manual service valve when installing a gauge manifold necessary? If the water entering a water cooled condenser is 80°F, what would the leaving water temperature be? Zeotropes must leave the cylinder as a liquid but azeotropes may leave the cylinder as either a liquid or a vapor. The saturation temperature of the refrigerant in the system can be read on the refrigeration gauges: On the inside colored scales of the gauge. A refrigeration system dataplate states that the low side test pressure is 150 psig. In which system does less refrigerant enter the cylinder for each compression cycle, requiring more horsepower for each BTU of cooling? What is the maximum safe storage temperature for refrigerant cylinders? Dental pulp testing is a useful and essential diagnostic aid in endodontics. Only pressures above atmospheric pressure. Why can a compound gauge not indicate when a system is properly evacuated? Symptoms of exposure to dangerous levels of R-410A include dizziness, headache, confusion, cardiac irregulari-ties, and loss of consciousness in extreme cases.If a leak is present or suspected, a suitable leak detector should be used to determine the need for ventilation orrespiratory protection. <> A mechanical refrigeration system cools a room by: The four types of cooling mechanisms are: Evaporative, Thermoelectric, Absorption, Mechanical Compression. The small line on a split system air conditioning unit is the: On the high side just after the condenser. Refrigerant that has been reprocessed to at least the purity specified in the ARI Standard 700 is considered: It become illegal to vent replacement refrigerants in: How do the recovery levels for Type III equipment differ from recovery levels for other types of equipment? If they travel through an unusually hot space. Increases the static pressure drop across the coil. Manual valves on the compressor suction and discharge and on the liquid receiver. How can scaling be reduced in water towers? %PDF-1.5 What is the maximum reading on a typical R410a compound gauge? A compressor that uses an impeller to throw refrigerant from the center outward is a: How can hermetic compressors be characterized? Which type of condenser requires the most maintenance? The line that connects the evaporator to the compressor is called the: The refrigerant is a high-pressure, warm, subcooled liquid at the inlet of the metering device. If you do experience symptoms after an event, it can happen immediately or even some time afterwards. Beyond the HVAC&R industry, these same refrigerants have been used as blowing agents in the manufacturing of foams and insulations. What two pieces of information are necessary to measure the TEV superheat? The smallest increments displayed on most digital gauges are: A tool used for checking system pressures, evacuating systems, recovering systems, and charging systems is: Check valves on the end of refrigeration hoses: Automatically open and close when the hoses are connected and disconnected. You should wash opposite the direction of airflow. Which type of condenser uses a fan to push air across the condenser? This means that: The low side should not be pressurized above 150 psig. Constitutional symptoms are progressively more prevalent with advancing NTM lung disease. The lines inside the saturation curve that start at the bottom and extend upward toward the critical point are called: What pressure units are used on the enthalpy diagram? A system using R-404a has an evaporation temperature of 0°F. DISTRIBUTOR: National Refrigerants, Inc. 661 Kenyon Avenue Bridgeton, New Jersey 08302 ... symptoms of asphyxiation, loss of coordination, increased pulse rate and deeper respiration ... combustible when mixed with air under pressure and exposed to strong ignition sources. It has a slight odor like ether. In leak detection, R-22 is used in conjunction with which of the following? Besides distributing the refrigerant evenly, a refrigerant distributor also: Creates a pressure drop across the distributor. How is the type of service pressure of a recovery tube identified? Refrigerants commonly used in fairly modern systems are R-22 (HCFC-22)and R410A, sold under names like SUVA410A and Puron. What type of units are required by the EPA to have service valves? What units are used to measure pressure in the SI system? A restricted inlet screen on a TEV can cause: Low suction pressure, high superheat, and high subcooling. For support following a traumatic event or critical incident contact: your manager or supervisor; human resources team Which refrigeration device would most likely be installed in the discharge line leaving the compressor to prevent liquid refrigerant from draining from a raised condenser into the compressor head? There is a small amount of water drained off the cooling tower sump. What is the best pH level to maintain in a water tower? It moves the heat from the refrigerated area to another area. An evaporator that covers the coils being cooled with liquid refrigerant is a: The most common types of defrost for commercial refrigeration evaporators are: Water that condenses on an evaporator coil and is blown off by the velocity of the air through the coil is called condensate: Why might there be a negative pressure on the condensate outlet in a coil operating at a positive static pressure? Balanced port valves can retain good control over a wider range of operating conditions. If they are exposed to cold temperatures that could cause the refrigerant to condense in the line. What effect does this have on the system? Which compressor type draws refrigerant gas in through the inlet port into voids created by turning rotors? Compared to air conditioning evaporator coils, commercial refrigeration coils have: The water is in the shell and the refrigerant is in the tubes. Entropy is the ratio of heat content to absolute temperature. The preferred method for raising the pressure of a low pressure chiller in order to test for leaks is: Circulating warm water through the chiller. Can reduce system efficiency because of a high pressure drop. Why is it necessary to purge gauge manifold valves while they are connected? Compressor cylinder unloading reduces the capacity of a reciprocating compressor by: Making the valves in the head inoperative. The order of the four main components of the refrigeration cycle is: Compressor - condenser - metering device - evaporator. The advantage of compliance in a scroll compressor is that: The orbiting scroll can separate and unload to pass a small liquid slug. When a manual service valve is front seated: The service port is open and the system is closed to the line. Refrigerant that has been removed in any condition from an appliance and stored in an external container without necessarily testing or processing it in any way is considered: Does not rely on the system the refrigerant is being recovered from for its operation. 12°F × 0.5%/°F = 6% increased capacity. Leaks in industrial process cooling systems must be repaired if they have an annual leak rate of: Why is a pressure regulator necessary when using nitrogen cylinders? The line that connects the condenser to the metering device is called the: The discharge, liquid, and suction lines of a packaged unit are: The difference between a liquid receiver and a suction accumulator is that: Receivers only allow liquid to leave while accumulators only allow vapor to leave. If your symptoms are distressing or last for more than a few weeks, you should see a health professional to ask for help. The first check to make whenever working on a water-cooled system is: In a water-cooled condenser, what does an increase in head pressure and a decrease in temperature difference across the condenser indicate? Sometimes these get mixed with honey and other secretions from the bees and stored in the honeycomb. The most accurate analog gauges available on gauge manifolds in the HVACR industry are: When do positive shut-off fittings reduce refrigerant loss? How can a technician determine when a filter-drier is stopped up and needs changing? If a technician needs to read the refrigerant pressure of a window unit, they must: After servicing a system using bolt-on piercing valves, the technician should: Recover the refrigerant, remove the bolt-on valve and replace it with a permanent valve. One difference between refrigerant piping practices for air conditioning systems and refrigerant piping practices for commercial refrigeration systems is that: Most air conditioning manufacturers do not recommend oil traps. endobj Heated diode leak detectors are not as prone to false alarms. The space left between the piston and the valve plate of a reciprocating compressor when the piston is at the top of the cylinder is called: What opens and closes the valves in a reciprocating compressor? As the refrigerant passes through the condenser, the refrigerant is: De-superheated, condensed from a gas to a liquid, and subcooled. ... cleaning agents and refrigerants. What refrigerants can be detected with a halide torch? One operating advantage of fixed restriction metering devices over expansion valves is: Can be used with low starting torque compressor motors. Only when other diagnostic means have been exhausted. It is possible for the same air conditioner to have a different capacity and efficiency with each coil it is matched to. The symptoms of NTM pulmonary disease are variable and nonspecific. Why is it dangerous to drill out orifices in metering devices? Leaks in refrigeration systems other than air conditioning systems, commercial refrigeration systems, or industrial process cooling systems must be repaired if they have an annual leak rate of:`. What are the most common desiccant materials used in driers? Medium-temperature applications are usually between: Which of the following is a type of sports arena that uses flooded evaporators? Refrigerant increases in volume as it travels through the: An isothermal process is a process which does not change: Which of the refrigerant ratings indicates that a refrigerant is considered a higher toxicity refrigerant?
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