Because of the latent heat load, refrigeration machine operator was instructed to start the reciprocating plant for air conditioning. Of the following according to recommended practice, the first thing to do is:
Turn on chilled water pumps and open the bypass to lighten the load
Install larger fuse to take the initial load and then turn on the cooling tower fans
Turn on chilled water pump, condenser water pumps and cooling tower fans
Set thermostat a few degrees higher
The most important reason to use 2 compressors in a cascade system is to :
Accomplish lower temperature
Permit the use of inexpensive lubrication oil
Avoid the need for very high compression ratios
Divide the cooling load between 2 compressors
The advantage of forced draft over natural draft cooling tower is
The possibility of lower water out temp
There is no dependence on natural wind velocity
Use of a smaller tower size
All of the Above
what is 29.92" HG in Kpa
101.3
101.28
101.26
103.2
The rupture disk is always piped into the
High side
Low side
Either side of the system
Neither side of the system
A fusible plug melts at
450 F
280 F
212 F
800 F
When will the BTUs absorbed by the condensing water be the greatest?
Low cond temp, low cond water temp
High cond temp, High cond water temp
High Cond temp, Low Cond water temp
Low Cond temp, High Cond water temp
Flooded Evaporators have high heat transfer per square foot, What may be a disadvantage?
Requires a smaller charge
Requires a larger charge
Requires the use of a TXV for proper feed
Water has to be drained daily
Shell and tube condensers have the advantage of
Removing heads for cleaning the water sides of the tubes
The refrigerant connections do not have to be disrupted
Using acid for cleaning
Both A and B are correct
Shell and coil condensers have the advantage of
Removing the heads for cleaning the water sides of the tubes
Has less of a chance of developing leaks
How many BTUs would be removed in a 30 ton system?
12,000 per hour
360,000 per minute
12,000 per minute
360,000 per hour
If you have 62 psi at 35 F and 70 psi at 45 deg F, what would 38 deg F be?
66
64.4
65
62
Copper is used in refrigeration systems, like in heat ex-changers because?
Easy fabrication
Easy durability
High thermal conductivity
Flexability
The accessories on the liquid line are in what order?
solenoid valve, drier, and sightglass
receiver, drier, solenoid valve, and sightglass
muffler, drier, sightglass, and solenoid valve
accumulator, muffler, drier, sightglass
A condenser is 20' long and 6' in diameter, what is the volume in gallons if 7.48 gallons is 1 cu/ft?
565
4227
1808
1205
If the low pressure cutout cycles the compressor off, what starts the compressor again?
Solenoid valve
High pressure cut out
Low pressure cut out
Thermostat
Removing insulation on the suction line with the engine room temp at 85F, what will occur?
Flooded evaporator
Starved evaporator
Excessive superheat
Low superheat
If you were running three compressors, which best describes the state of refrigerant leaving the third evaporator coil?
Mostly liquid, some vapor
Mostly vapor, some liquid
Superheated vapor
Highly superheated vapor
An electric motor that is rated at 3 HP will?
Use three phase
Need a capacitor
Use a single Phase
Will run with reduced power output
In a 3 stage centrifugal chiller, what happens to the pressure as it reaches the final stage?
Increases
Decreases
Speed changes not pressure
Volume changes not the pressure
With an induced draft cooling tower, what is the lowest temperature attainable for a cooling tower?
Wet bulb equal to dry bulb
Dry bulb slightly lower than wet bulb
Dry bulb higher than wet bulb
Wet bulb can never be lower than dry bulb
When a compressor is running fine at full flow and you throttle down flow causing the compressor to stop running normal (short cycle), why would this happen?
Dirty filter/ strainer
Air getting in seals
High head pressure
When dry bulb is 75F and wet bulb is 75F?
Not possible
Very low humidity
Thermometer is defective
100% relative humidity
When a compressor is said to have a safety head this means :
Compressor operates with normal pressures
Compressor operates with low pressures
Compressor has a pressure relief device
Compressor has high pressure cut out
The cylinder unloader controls capacity, is there any other function it may have?
Assist with compressor shut down
Assist with compressor start up
There is no other function
Releases pressure for protection
An operator suspects that shorted motor windings have caused the motor overloads to trip. In order to investigate this condition, the operator would be most correct to use :
Capacitor
Voltmeter
Ohmeter
Ammeter
When recovering R22, What color would the cylinder be that you are storing the refrigerant in?
Yellow tops
White tops
Green tops
Gray tops
If unloaders were to fail in the unloaded position, what happens in a system using reciprocating compressor?
The evaporator will starve
Cause high superheat
Not enough refrigerant to coil
All of the above
When the temperature and the load increase and you need to add another pump online, you would :
Close both suction and discharge
Open both suction and discharge
Open suction and throttle discharge
Open discharge bypass and close suction
When a system does not have unloaders, what is needed?
Other capacity control
Variable inlet guide vanes
An economizer
Solenoid on liquid line
When an evaporator is not equipped with an equalizer line, you would most likely find
Feeder bulb placed in different area
A distributor
An automatic expansion valve
Both high and low side pressures identical
When you plan on overhauling a system and you have recovered all liquid refrigerant, what is next?
Go ahead and do the work
Recover all vapor, then do the work
Send liquid nitrogen through
Evacuate system
When there is a 5lb pressure drop across evaporator, you need an external equalizing line, what happens if it disconnects?
Evaporator would starve
Evaporator would flood
TEV would not function
The metering device used in a condenser is a high side float, this device will :
Control the amount of water in condenser
Control the amount of refrigerant in condenser
Keeps a constant pressure
Keeps a constant temperature
If a low side float is being used :
Pressure will be constant
It will control refrigerant flow
It will control water flow
Temperature is constant
The heat that boils off in a condenser is :
Latent heat
Sensible heat
Superheat
The condenser that uses air and water for cooling is the :
Air cooled
Water cooled
Evaporative
Both a and b are correct
A hermetic compressor is operating with a low refrigerant charge, What is the most likely effect this condition would have on the compressor?
Head pressure would rise
Compressor would operate at higher temperature
Have no effect on the compressor
Oil pressure would rise
A centrifugal chiller has a suction pressure of 18" Hg vacuum and discharge pressure of 6 psig. What is the compression ratio of this unit ?
3.50
2.96
1.75
2.76
If you had to install a solenoid valve to a system which uses 110 volts and needed to convert it to 24 volts, what would you use?
Step up transformer
Step down transformer
AC to DC rectifier
Rewire circuit with smaller gauge wire
If you had 38 degrees in the evaporator, what should you suction pressure be for R22?
66 Psia
66 Psig
76 Psig
76 Psia
An oil with low viscosity would :
Not be used for refrigeration
Be used for engine/motors
Be used for air conditioning
Both B and C are correct
When charging a centrifugal system the position of the valve is :
Front seated
Back seated
Cracked off the back seat
Closed
The suction and discharge valves in a reciprocating compressor are positioned :
Over valve plate
Under valve plate
Both under and over valve plate
None of the above
What refrigerants are you not able to dump?
CFC
HCFC
HFC
Any refrigerant containing chlorine or flourine
There is an automatic water regulating valve on a reciprocating chiller. Water is entering the condenser at 85F and leaving the condenser at 88F. You know there is no scale and the tubes are not covered with film. What can be causing this condition?
Low suction pressure
Water valve stuck open
Water valve stuck closed
How low can chiller water temperature be?
32 degrees F
33 degrees F
38 degrees F
42 degrees F
While using a halide torch to check for refrigerant leaks, if the flame was to turn yellow, what happened?
Container is empty
Restriction in tube
Refrigerant is leaking
Refrigerant has high moisture content
What is the cubic feet of a 20' long 6' vessel on the evaporator?
120 cubic feet
565 cubic feet
4,235 cubic feet
4,710 cubic feet
A water regulating valve is installed in a water cooled condenser. The operating force on this valve is respondent to :
High side pressure
Chilled water temperature
Circulating water pressure through the condenser
Manual operation
Compound gauges can measure:
Above atmospheric
Below atmospheric
Temperature
A low pressure refrigeration system has a pin hole in the evaporator. What is the most likely result?
Frost around leak area
High condenser water pressure
Low condenser water pressure
What does the centrifugal compressor generate inside?
High pressure, low velocity
High volume, low pressure
Low velocity, Low pressure
High velocity, high pressure
Oil flashpoint temperature in the compressor should be :
Lower than the heat of compression
Higher than the heat of compression
Equal to the heat of compression
Equal to the heat absorbed
Compressor motors that operate inside the refrigerant atmosphere (atmospheric) :
Must use materials compatible with the system refrigerants
Motors must be assembled in clean atmosphere and kept dry
Are not worked on in the field
In a centrifugal three stage compressor:
Pressure increases with each stage
Impellers are same size
Impellers increase with each stage
An operator suspects that a vertical check valve on a discharge of a centrifugal pump is defective, this is a condenser pump and one of three pumps in parallel. If the suspicion is true and the check valve fails to seat when required, the pump and connecting piping will most likely be damaged when :
Lubricating the pump
After having bled air from the pump casing petcock
Starting an additional pump
Shutting the pump down
In relation to the suction pressure of a compressor, The reading in the oil pressure gauge should read :
15-30 psi lower
60-90 psi higher
15-30 psi higher
30-60 psi lower
The following most accurate statement regarding compressor motors that run in a refrigerant atmosphere is that they :
May use internal rubber cushions
May be repaired on site when they malfunction
Use materials tailored to the refigerant
Use same materials as a pump in air
The following is an example of an "inline" refrigerant cleaning system which may be used with a centrifugal compressor containing R123 refrigerant is :
Refrigerant recovery
Refrigerant disposal
Refrigerant reclaiming
Refrigerant recycling
Regarding fire safety ANSI/ASHRAE, which classification indicates the latest flammability and least toxicity?
A1
B2
A2
B1
Bubbles in the sight glass are most likely caused by :
An overcharged system
Non-condensable gases
Light load on the plant
Partially plugged filter/drier
In addition to regulating the refrigerant flow according to the needs of the system, metering devices also serve to :
Increase compressor capacity
Hold system to a constant load
Restrict flow of refrigerant from the high side to low side
Shed load as load increases
Regardless of safety classification of the refrigerant in use, in the event of refrigerant escape, the RMO should be aware of :
A refrigerant fire
Refrigerant poisioning
Oxygen deprivation
Atmospheric superheating
The refrigeration unit which you have been assigned to is being taken out of service for major repairs. You have been assigned to withdraw refrigerant for storage in suitable containers. According to the NYC fire law handbook you must ensure that containers :
Are approved by the US department of transportation
Are approved by the facilities manager
Do not weigh more than 200lbs when filled
Do not exceed 55 gallon capacity
An operator confirms that a chiller water pump in a refrigeration system employing R123 is cavitating, of the following, the most likely cause for this condition is :
Malfunctioning of the water makeup float valve
Too much time in between pump servicing
Operating at sustained high loads
Lowering the chilled water temperature
An RMO is logging readings from a reciprocating compressor-refrigerating unit. The crankcase and compressor discharge temp have dropped significantly and suction line pressure is high. Of the following the one that may cause this set of conditions is:
Compressor cycling
An expansion valve which is closed too much
An expansion valve which is open too wide
Faulty compressor valves
The Ratio of actual pressure of water vapor in the atmosphere to the saturation pressure / temp is called :
Absolute humidity
Humidity effect
Partial pressue
Relative humidity
The dividing line between the high and low sides of the refrigeration system is :
The connection between the compressor and condenser
Needle valve mechanism
Compressor outlet and the orifice of the metering device
Center plate of the refrigeration mechanism
An RMO verifies that a condenser water pump is cavitating in a refrigeration system employing R22 refrigerant. Of the following the most likely cause for this condition is:
Air leaks through the pump packing
Faulty cooling tower water level controller
Too long a period between pump servicing
An operator notices that a centrifugal pump operates satisfactorily when delivering at full discharge, but loses water flow if throttled. The operator would most accurately assume that this condition is due to:
Water hammer
Clogged strainer in pump inlet
Poor bearing lubrication
Air leaks in the pump
Assuming that a refrigeration plant uses a horizontal shell and tube condenser with the water in the tubes and the refrigerant in the shell. In controlling the operation of the condenser, the operator should take into account that most likely the heat transfer rate BTU/per sq ft per second in the condenser will :
Show the least benefit for descaling tubes at high water velocity
Increase with the velocity of water in the tubes
Increase with lower log mean temperature difference
Show only a small increase if the tubes are descaled
Electric devices may be used to provide built in defrosting of refrigeration machine evaporator units. These devices are classified as:
Relays
Induction coils
Capacitors
Resistors
Latent heat and refrigeration effect are usually listed as refrigerant properties. The refrigerating effect is also always a lower value than the latent heat because the :
Heat required to cool the refrigerant from compressor discharge to evaporative temp is subtracted from the latent heat
Refrigerant latent heat is divided by specific gravity of the refrigerant
Refrigerant critical temperature is factored into the calculation of the refrigerating effect
Refrigerant latent heat is divided by the refrigerant circulation rate
Superheated vapor flowing into a reciprocating compressor protects the compressor parts against liquid intake. Of the following, one of the problems associated with superheat is that:
Non-condensables are more prone to collect in the system
Frost may develop in the suction line
It will decrease the capacity of the compressor and the refrigeration machine
The compressor head pressure drops too low
An operator observes a reading of 60c on a refrigerating unit. The same reading in F scale would be closer to: (x1.8+32)
140
185
155
170
What is the state of refrigerant as it leaves the compressor and as it leaves the condenser:
Superheated vapor and superheated liquid
Superheated vapor and warm subcooled liquid
Saturated Vapor and cold sub cooled liquid
Saturated vapor and warm sub cooled liquid
Clearance volume:
Affects compressor capacity
Is the space that traps liquid refrigerant
Varies, depending on compressor speed
Is the same on all compressors
A Thermal is attached to the suction pipe between the evaporator coil and the compressor covered by an insulating line. Assuming the machine room is 85F unraveling of the insulation would result in:
Adequate superheat
Flooded Evaporator
Of the following one of the primary reasons for the insulation of a crankcase breather line is :
Increase the compressor efficency
To prevent oil slugging in the compressor
Keep the shaft packing lubricated
To prevent refrigerant from entering the compressor suction
A RMO notices excessive cycling of the temp control for a reciprocating compressor refrigeration unit. The crankcase temp is high, the compressor discharge temp is low and the suction line is high, of the following the one that may be causing this set of conditions is:
Purge unit operation
An expansion valve that is open too wide
Condenser operation, dirty tubes, or cooling water control
A reciprocating system using an evaporative condenser, the muffler is installed between:
Evaporator and Compressor
Receiver and expansion valve
Compressor and evaporative condenser
Receiver and condenser
While operating an R12 reciprocating system, the RMO noticed the oil foaming the in the crankcase. This condition most likely would have been caused by:
Addition of liquid freon
Sudden drop in oil Temp
Sudden drop in crankcase pressure
Addition of oil to the crankcase
Assume that a new valve plate has been installed while they are repairing a reciprocating compressor in a refrigeration plant. The installation of a new valve plate will require the replacement of:
All valve plates, springs and some valve seats
All valve and valve seats
Valve seats only
Suction Valves only
During a hot weekend, RMO is instructed to start additional reciprocating machine. The sequence of actions on startup would most likely be:
check compressor oil, start cooling towers, check valves are in correct position, turn on machine, start chiller and condenser water pumps
start chiller and condenser water pumps, start cooling water tower fans, check compressor oil levels, check that valves are in correct position, turn machine on
turn machine on, check valves are in correct position, start tower fans, check compressor oil levels, start chiller and condenser water pumps
check valves are in correct position, start cooling water tower fans, start machine, start chiller and condenser water pumps, check compressor oil levels
While doing a routine inspection, the RMO noticed the bulb of the TEV on the floor, the operator should attach the bulb at:
center of the coil
expansion valve outlet
end of coil
3/4 away towards the end of the coil
When operating a reciprocating refrigeration system with a belt driven compressor, an RMO notices that one of the 4 belts is broken. Of the following, the most advisable course of action for the RMO would be to:
Put more grease on the remaining belts
Replace all 4 belts with a new set
Replace the broken belt only
Operate with the remaining 3 belts
An operator reads the valve tag on a pressure relief valve and notices that the valve is set to unseat at an evaporator pressure of 15 psi, The corresponding set pressure in inches of HG is :
18
14
20
30.3
What is the maximum percentage that a refrigerant can be stored in a cylinder?
75%
80%
90%
100%
