Unit 48: Pop Test 6/ Unit 49: Homework 7/ Unit 48: Homework 6/ Unit 48: Pop Test 5
For each 1°F of added subcooling, the efficiency of a system will increase by approximately a. 3%. b. 5%. c. 1%. d. 7%.
C
Circulating water throughout a building to provide comfort cooling is desirable from an economic standpoint because a. water is less expensive than refrigerant. b. water is lighter than refrigerant. c. water does not require the use of a pump to move it through the system. d. the design chilled water temperature is lower than the design boiling temperature of the refrigerant
A
Electronic starters are much smaller than conventional starters. a. True b. False
A
Excessive buildup of minerals in the cooling tower water can result in a. reduced heat transfer between the refrigerant and the condenser water. b. increased heat transfer between the refrigerant and the chilled water. c. increased heat transfer between the refrigerant and the condenser water. d. reduced heat transfer between the refrigerant and the chilled water.
A
High pressure chillers use either air- or water-cooled condensers. a. True b. False
A
In a cooling tower blower assembly, why are beveled gears preferred over non-beveled gears? a. Beveled gears have more surface area between the mating surfaces. b. Beveled gars tend to wear out faster than non-beveled gears. c. Non-beveled gears tend to last longer than beveled gears. d. Beveled gears have less surface area between the mating surfaces.
A
In order for centrifugal pumps to operate properly a. the eye of the impeller must be below the water level. b. the entire impeller must be above the water line. c. the entire impeller must be below the water line. d. the eye of the impeller must be above the water level.
A
On a close-coupled pump, the impeller is a. mounted directly on the motor shaft. b. turned by means of a belt-driven assembly. c. rotated at a speed that is different from that of the motor. d. connected to the motor shaft using a 90-degree linkage.
A
Regarding cooling towers, a foot valve is a type of a. check valve. b. globe valve. c. butterfly valve. d. ball valve.
A
The condenser water pump is usually a centrifugal pump. a. True b. False
A
The cooling tower component referred to as fill can be made of all of the following except a. steel. b. wood. c. fiberglass. d. plastic.
A
The heat transfer process within a cooling tower between the water and the air is ________. a. both latent and sensible b. latent c. sensible d. evaporative
A
The oil pump for a ___________ compressor is driven from the actual compressor shaft. a. reciprocating b. scroll c. centrifugal d. linear
A
The strainer in a cooling tower is located a. at the point where the water leaves the cooling tower. b. in the pipe that carries water from the condenser to the cooling tower. c. in the cooling tower's makeup water line. d. at the point where the water enters the cooling tower.
A
The superheat maintained by a thermostatic expansion valve is typically between a. 8°F and 12°F. b. 4°F and 8°F. c. 0°F and 4°F. d. 12°F and 16°F.
A
The system component that eliminates the constant starting and stopping of a cooling tower's fan is the a. variable frequency drive. b. external transmission drive. c. gearbox drive. d. internal transmission drive.
A
The temperature difference between the entering and leaving water of the cooling tower is referred to as __________. a. tower range b. TD c. approach d. water differential (WD)
A
The term "feet of head" is used to express a. pump capacity. b. fan capacity. c. system capacity. d. compressor capacity.
A
The two float-type metering devices are the a. high-side float and the low-side float. b. liquid float and the vapor float. c. liquid float and the low-side float. d. vapor float and the low-side float.
A
The valve type used most commonly on small lines are a. diaphragm valves. b. service valves. c. gate valves. d. ball valves.
A
What is the approach temperature for an R-410A chilled-water system that produces 43°F water when it operates with an evaporator saturation pressure of 112 psig? a. 6°F b. 10°F c. 8°F d. 4°F
A
What system component(s) must be started before the compressor in a chilled-water system centrifugal chiller? a. Chilled water pump, condenser water pump, and the oil pump b. Crankcase heater and the oil pump c. Cooling tower fan motors d. Chiller barrel heater, oil pump, and cooling tower fan motors
A
When referring to cooling tower construction, the acronym FRP stands for a. fiber-reinforced plastic. b. fiber-reinforced polymer. c. flexible-reinforced polymer. d. flexible-reinforced plastic.
A
When referring to evaporators, the terms "direct expansion" and "dry type" can be used interchangeably. a. True b. False
A
Which of the following best describes a centrifugal pump found on cooling towers? a. Brass or bronze impeller mounted on a stainless-steel shaft b. Bronze impeller mounted on a brass shaft c. Copper impeller mounted on a stainless-steel shaft d. Stainless-steel impeller mounted on a stainless-steel shaft
A
Which of the following components can be found in a cooling tower's sump? a. A water heater and a strainer b. Only a water heater c. Only a strainer d. Neither a water heater nor a strainer
A
Which of the following statements is true regarding package-type chillers? a. They require field-installed water lines. b. They require no field-installed lines whatsoever. c. They require field-installed refrigerant and water lines. d. They require field-installed refrigerant lines.
A
A centrifugal compressor starts unloaded and only begins to load up after the motor is up to speed. This is accomplished using a. a separate oil sump. b. prerotation guide vanes. c. permanently installed pressure gauges. d. crankcase heat.
B
A chiller barrel that has three passes will most likely operate with a design approach temperature of about a. 1°F. b. 5°F. c. 9°F. d. 13°F.
B
A mixing valve is manufactured with a. one inlet port and one outlet port. b. two inlet ports and one outlet port. c. two inlet ports and two outlet ports. d. one inlet port and two outlet ports.
B
A technician can verify waterflow through the condenser of a chiller by a. running the purge unit and checking its discharge for bubbles. b. checking the pressure drop from the inlet to the outlet. c. checking the amperage of the evaporator water pump. d. checking the superheat and comparing it to the log.
B
A variable frequency drive (VFD) is used to vary the a. amperage draw of the system's motors. b. number of cycles per second of the power supplied to the system's motors. c. resistance of the system's motors. d. voltage supplied to the system's motors.
B
Before starting up a chiller a. the chiller and condenser water should be drained. b. the crankcase heater should be energized for a period, typically 24 hours. c. the compressor oil should be drained, cooled, and then recharged. d. nitrogen should be added to the system to raise the pressure for a leak test.
B
Capacity control on a centrifugal compressor is accomplished by the a. postrotational guide vanes. b. prerotational guide vanes. c. check valves. d. slide vanes.
B
Corrosion in a cooling tower comes from all of the following except a. chemical additives. b. hard water. c. slime. d. mineral scale.
B
Encapsulation and electroporation are two methods that can be used to control a. drift in a cooling tower. b. bacterial growth in a cooling tower. c. evaporation of tower water. d. airflow in a cooling tower.
B
How are seals on circulator pumps typically lubricated? a. Oil b. Water c. Refrigerant d. Brine
B
If a cooling tower is equipped with two or more cells, what can be done to ensure that the water flow to each cell is the same? a. Stagger the blowdown cycles for each cell b. Install a balancing valve on each cell c. Use separate water feed lines for each cell d. Control tower makeup water from a central location
B
In the crossflow cooling tower configuration a. the air flows down and the water flows at a 90-degree angle to the air. b. the water flows down and the air flows at a 90-degree angle to the water. c. the water flows up and the air flows down. d. the water flows down and the air flows up.
B
Lithium bromide is ideal for use in absorption systems because it is non-corrosive. a. True b. False
B
Low pressure chillers use either air- or water-cooled condensers. a. True b. False
B
On a centrifugal chiller start-up, the oil sump temperature should be at least _____°F, depending on the manufacturer. a. 105°F to 135 b. 135°F to 165 c. 50°F to 85 d. 75°F to 105
B
The __________ helps to maintain the correct tower water temperature at the condenser during start-up and during low ambient. a. surge tank b. tower bypass valve c. tower sump d. auxiliary heater
B
The capacity of a chiller operating with a rotary screw compressor is most likely controlled by a a. check valve on the compressor's discharge side. b. slide valve on the compressor's suction side. c. check valve on the compressor's suction side. d. slide valve on the compressor's discharge side.
B
The scroll compressor is equipped with an internal check valve to a. maintain the system's low-side pressure below a preset maximum level. b. prevent backward refrigerant flow when the system compressor cycles off. c. maintain the system's high-side pressure above a preset minimum level. d. prevent system superheat from rising above its design set point
B
The two methods for controlling bacteria are ___________. a. alcohol and salts b. encapsulation and electroporation c. chemical pellets and bleach tablets d. chlorine tablets and electroporation
B
The two types of shaft seals on the pump are ___________. a. wax seal and flexible seal b. stuffing box and mechanical seal c. flexible seal and mechanical seal d. wax seal and stuffing box
B
The typical condensing temperature for the refrigerant in a water-cooled chilled water system is a. 85°F. b. 95°F. c. 105°F. d. 115°F.
B
Thermostatic expansion valves are the only metering devices used in high pressure chillers. a. True b. False
B
To unload a reciprocating compressor, hot gas bypass across the cylinder is the best method. a. True b. False
B
Two types of seals found on pumps are the a. mechanical seal and the centrifugal seal. b. stuffing box and the mechanical seal. c. mechanical seal and the pressure seal. d. packing gland and the centrifugal seal.
B
Two types of three-way bypass valves that may be used are the mixing valve and the tower bypass valve. a. True b. False
B
When condenser tubes become fouled, they may be cleaned by a. running a mixture of sand and water through them. b. using a brass brush. c. using a steel brush. d. using a chisel and hammer.
B
Which type of pump seal is typically used for pressures up to a maximum of 150 psig? a. Mechanical seal b. Stuffing box c. Pressure seal d. Packing gland
B
Which type of pump seal is typically used for pressures up to a maximum of 300 psig? a. Pressure seal b. Mechanical seal c. Centrifugal seal d. Stuffing box
B
A diverting valve is manufactured with a. one inlet port and one outlet port. b. two inlet ports and two outlet ports. c. one inlet port and two outlet ports. d. two inlet ports and one outlet port.
C
A makeup water is required for cooling towers because of a. evaporation only. b. drift only. c. both evaporation and drift. d. neither evaporation nor drift.
C
All low-pressure chillers use which type of compressor? a. Rotary b. Reciprocating c. Centrifugal d. Scroll
C
Both spray pond and natural-draft cooling towers rely on ________ to move air through them. a. centrifugal pumps b. mechanical blowers and fans c. prevailing winds d. solar-powered fans
C
Cooling towers require blowdown in order to a. increase the concentration of minerals and other contaminants in the tower water. b. prevent the cooling tower's sump from overflowing. c. reduce the concentration of minerals and other contaminants in the tower water. d. prevent the water in the cooling tower from freezing.
C
Evaporators that operate with an established amount of superheat are referred to as a. low-side float evaporators. b. high-side float evaporators. c. direct-expansion evaporators. d. flooded evaporators
C
For an approach temperature of 10°F, what is the temperature of the water leaving a condenser if the condenser saturation pressure is 344 psig for an R-410A system? a. 85°F b. 75°F c. 95°F d. 105°F
C
If a cooling tower rejects 100 tons of heat, approximately how much of the rejected heat is attributed to the system's compressor? a. 5 tons b. 15 tons c. 20 tons d. 10 tons
C
If the compression ratio on a centrifugal compressor rises too high, the compressor will stop pumping and make a loud sound commonly referred to as a a. purge. b. merge. c. surge. d. splurge.
C
In a gearbox or transmission drive assembly on a cooling tower the motor shaft and the fan shaft are at an angle of ________ degrees with each other. a. 60 b. 30 c. 90 d. 45
C
Insufficient water flow through a cooling tower can result in a. high head pressure and low suction pressure. b. low head pressure and high suction pressure. c. high system operating pressures. d. low system operating pressures.
C
Oil pumps used in conjunction with centrifugal compressors typically use a. three-phase, multi-horsepower motors. b. single-phase, multi-horsepower motors. c. three-phase, fractional horsepower motors. d. single-phase, fractional horsepower motors.
C
The electronic expansion valve relies on a. the difference between the condenser and evaporator outlet temperatures to control the valve. b. pressure transducers to maintain the desired evaporator saturation pressure. c. pressure transducers and thermistors to control the operation of a stepper motor. d. the difference between the system's high and low pressure to control the valve.
C
The flow through an orifice metering device a. is constant under all operating conditions. b. decreases as the pressure drop across the orifice increases. c. is constant as long as the pressure drop across the orifice remains the same. d. increases as the pressure drop across the orifice decreases.
C
Vortexing in a tower is best described as a(n) a. dilution of cooling tower chemicals. b. overconcentration of cooling tower chemicals. c. whirlpool action. d. mixture of water and air.
C
What component is incorporated into the marine water boxes to direct water through a shell-and-tube heat exchanger? a. Converters b. Diverters c. Partitions d. Abscissions
C
What system component is used to move water through the condenser and cooling tower? a. Centrifugal fan b. Perpetual pump c. Centrifugal pump d. Perpetual fan
C
When a winterized reciprocating compressor is restarted a. the crankcase heater must be deenergized 24 hours prior. b. it will run at ½ capacity for the first 24 hours. c. it will start up unloaded until the oil pressure builds up. d. the low-pressure control must be isolated from the system.
C
Which of the following is true regarding forced-draft and induced-draft cooling towers? a. Forced-draft towers pull air through them and induced-draft towers push air through them. b. Both types of cooling towers rely on prevailing winds to move air through them. c. Both types of cooling towers use mechanical fans and blowers to move air through them. d. Both types of cooling towers have air pulled through them.
C
Which of the following represents the most complete and accurate list of possible system capacities for a chilled-water system that is equipped with one 10-ton and one 15-ton scroll compressor? a. 10 tons and 15 tons b. 15 tons and 25 tons c. 10 tons, 15 tons, and 25 tons d. 0 tons and 25 tons
C
Why is it sometimes required for open cooling towers to be equipped with "tower wetting systems"? a. To prevent algae and other biological contamination growth. b. To prevent the wood and plastic in the tower from becoming brittle. c. To reduce the potential for fire in the cooling tower. d. To reduce the formation of scale on the exterior surfaces of the tower.
C
The pressure difference in a low-pressure chiller is produced by a(n)____________ compressor.
CENTRIFUGAL
All cooling towers must have some sort of ________ for collecting the water. a. surge tank b. water box c. chiller barrel d. sump
D
An adiabatic process is one that results in a change in a. temperature, heat content, and pressure. b. heat content and temperature. c. heat content but no change in temperature or pressure. d. temperature and/or pressure but no change in heat content.
D
Before moving the valve stem of a service valve that has accumulated rust a. the protective cap should be put back in place. b. the refrigerant should be recovered. c. the refrigerant should be pumped into the receiver. d. the rust should be sanded down with a fine sand cloth.
D
Galvanized steel does not readily rust because the steel is coated with a. brass. b. aluminum. c. copper. d. zinc.
D
How is a packing gland tightened? a. With a wrench b. With a Phillips screwdriver c. With a Torx screwdriver d. By hand
D
If the outside ambient temperature has a dry-bulb temperature of 95°F and a wet-bulb temperature of 75°F, what is the cooling tower's approach temperature if the water is leaving the tower at 82°F? a. 13°F b. 27°F c. 20°F d. 7°F
D
In the counterflow cooling tower configuration a. both the water and air flow downward in parallel paths. b. both the water and air flow upward in parallel paths. c. the water flows up and the air flows down. d. the water flows down and the air flows up.
D
Most reciprocating compressors have a. a king valve. b. no clearance volume. c. a separate oil sump. d. a crankcase heater.
D
On a base-mounted pump, a. the pump and motor must be aligned in the field during installation. b. the pump turns at a speed that is different from that of the motor. c. the pump is connected directly to the shaft of the motor. d. a flexible coupling or connector is positioned between the pump and the motor.
D
The circuit that is used to energize the chiller's compressor is referred to as the a. compressor interlock circuit. b. main circuit. c. water pump interlock circuit. d. field control circuit.
D
The rate of heat exchange between two liquids a. is less than the rate of heat exchange between two gases as well as less than the rate of heat exchange between a gas and a liquid. b. is less than the rate of heat exchange between two gases, but greater than the rate of heat exchange between a gas and a liquid. c. is greater than the rate of heat exchange between two gases, but less than the rate of heat exchange between a gas and a liquid. d. is greater than the rate of heat exchange between two gases as well as greater than the rate of heat exchange between a gas and a liquid.
D
The removal of particles at the bottom of the cooling tower's basin can be accomplished by using a ____________. a. tower sump b. accumulator c. signal generator d. centrifugal separator
D
Using a hand-operated valve to control cooling tower blowdown is a. desirable because the length of the blowdown cycle will always be the same. b. desirable because blowdown will always occur at the same time each day. c. desirable because the water quality will be maintained at a constant level. d. not a desirable or recommended option.
D
What is the load on a cooling tower if 60 gpm of 95°F water enters the cooling tower and 60 gpm of 86°F water leaves the tower? a. 30 tons b. 15 tons c. 37.5 tons d. 22.5 tons
D
When pump cavitation occurs, a. the pump's vacuum is lost and the pump's noise level increases. b. the pump's vacuum is lost and the pump's noise level decreases. c. a partial vacuum is created and the pump's noise level decreases. d. a partial vacuum is created and the pump's noise level increases.
D
Which of the following is true regarding a high-pressure chiller equipped with an orifice metering device? a. The chiller operates with a reciprocating compressor. b. The chiller operates with 10°F of superheat. c. The chiller operates with R-410A as its refrigerant. d. The chiller has a critical refrigerant charge.
D
Which of the following is true regarding cooling tower fill? a. It should be kept dry at all times. b. Fill should be installed in a perfectly vertical position. c. Water should be directed to only one side of the fill. d. It should be kept wet at all times.
D
_______ is a whirlpool action that interferes with the functioning of the tower because it introduces air to the pump inlet. a. Cavitation b. Hydroplaning c. Blowdown d. Vortexing
D
In centrifugal compressors, capacity control is accomplished by the use of _________ at the impeller inlet.
GUIDE VANES
The pressure difference in an absorption chiller where the source of energy is steam or hot water is produced with the use of a(n) ___________ solution.
LITHIUM BROMIDE
The device that automatically helps to remove non-condensables from a chiller is called a(n)___________
PURGE UNIT
A chiller typically cools (what liquid?) for the purpose of air conditioning.
WATER
The refrigerant in an absorption chiller whose source of energy is steam or hot water is ____________
WATER
