WorksheetsSustainability Aircon Theory Revision
Total questions: 41
Worksheet time: 21mins
A sling psychrometer can be used to measure
flowrate and velocity
dry blub temperature and velocity
dry bulb temperature and wet bulb temperature
wet bulb temperature and flowrate
An infra-red thermometer is used to measure
Temperature
pressure
weight
sound
Which one of the following test is NOT used in predictive maintenance?
Vibration analysis
Acoustic analysis
Leak testing
Thermographic testing
A check valve in a piping system is used for
isolating flow
regulating flow
controlling flow direction
isolating and regulating flow
An air-conditioning system using a variable air volume system is NOT suitable for space where
latent heat is critical
humidity is critical
air flow is critical
pressure is critical
An elbow used in a water piping system to
regulated the water pressure
modulate the water flow
change the water temperature
change the water flow direction
What is the function of the cooling coil in an air handling unit?
To cool and dehumidify the mixing air
To cool and humidify the mixing air
To heat and humidity the mixing air
To heat and dehumidify the mixing air
When designing for a new building in Singapore, the room relative humidity of the air-conditioning system should not exceed
45%
50%
65%
70%
Four factors affecting thermal comfort are air temperature, humidity, air movement and
odour
air change
air volume
air cleanliness
The accessory that is used to trap impurities is the
filter-drier
suction line accumulator
check valve
receiver
Air properties can be determined by using a
psychrometric chart
graphical paper
Mollier chart
metric chart
Which one of the following accessories prevents liquid refrigerant from flowing into the compressor?
filter-drier
suction line accumulator
oil separator receiver
receiver
Which one of the following parts helps to reduce friction and the heat generated by the motor’s moving and rubbing parts and surfaces?
Bearing
Shaft
Rotor
Stator
A monthly maintenance program was to be established for the maintenance of the condenser and cooling tower water system in a new commercial building. Which one of the following tasks should be included in this program?
Clean water basin
Clean condenser tube
Clean strainers and filters
Check and adjust float valve water level
Which one of the following components forces air through the air distribution system?
Blower fan
Condensate pump
Compressor
Air volume control damper
The unit of measurement of sound is
decimetre
decibel
centimetre
gram
There was a concern that a chilled water pump might break down suddenly during operation. Which one of the following could be used to predict the likelihood of the pump breaking down?
Vibration analysis
Leak test
Pressure test
Locked rotor test
Low air velocity in the duct is up to
4 m/s
8 m/s
12 m/s
16 m/s
Large air-conditioning package systems can go up to
100 Tons
200 Tons
300 Tons
400 Tons
The function of a sound level meter used for predictive maintenance is to check for abnormal
noise due to bearing wear out
pressure due to leakage of refrigerant at the joints
temperature due to unbalanced motor load
refrigerant flow due to choked filter‐drier
In automatic control system, the desired condition of a variable to be maintained is called the
Setpoint
control agent
controlled variable
control point
One of the purposes of conducting maintenance work in a commercial building is
extend the lifespan of the equipment
lower the energy efficiency
increase the operating cost
increase the breakdown or system failure
One of the purposes of predictive maintenance is to
foretell the parts that are likely to fail
increase the energy consumption
increase the operation cost
reduce the power factor of the motor
During pressurize testing of the VRV/VRF air-cooled air-conditioning system, the pressure was found to have dropped after 12 hours. What could be the probable cause?
Air in the system
Pipe joint leak
Condenser fan not working
Shortage of refrigerant
The 4 main components of a chilled water air-conditioning system that are the necessary part of a vapour compression system are
evaporator, condenser, compressor and expansion device
air filter, compressor, fan motor and expansion device
condenser, compressor, filter drier and expansion device
evaporator, condenser, compressor and expansion device
Sensor is used in a control system to
process the data with other information
measure a variable and collect data
cause a control action
change the signal from one form to another
The function of the fins bonded to the evaporator coil is to
prevent refrigerant from flowing in the reverse direction
return oil back to the compressor
increase the heat transfer surface area
prevent liquid refrigerant from flowing into the compressor
Recently, a building was found to have the following conditions – office workers having headaches and respiratory problems, attributed to unhealthy factors in the working environment such as poor ventilation. This condition would be classified as
sick building syndrome
dry building syndrome
wet building syndrome
good building syndrome
The traffic light on the road is operated using time‐basis. The is an example of a/an
closed loop control system
feedback control system
open loop control system
sensor control system
The fan driven by a motor in an Air Handling Unit (AHU) is to
circulate the air
reduce the pressure of the air
condensed the water vapour in the air
trap the dirt from the air
Before performing maintenance work of the air-conditioning system
switch on the power supply
switch off the power supply
close all the windows and doors of the room
charge more refrigerant into the system
Which one of the following systems consumes the most energy in a typical commercial building?
Air-conditioning system
Lighting system
Security system
Fire protection system
If the fins bonded to the evaporator coil is to prevent refrigerant from flowing in the reverse direction
prevent refrigerant from flowing in the reverse direction
return oil back to the compressor
increase the heat transfer surface area
prevent liquid refrigerant from flowing into the compressor
The function of the electronic expansion valve used in a VRV/VRF air‐cooled air-conditioning system is to
modulate the refrigerant flow according to the load variation of the room
prevent liquid refrigerant from flowing into the compressor
return the oil back to the compressor
indicate the amount of moisture in the refrigerant
The function of a compressor is to
increase the discharge pressure level to the suction pressure level
maintenance the discharge pressure level to the suction pressure level
increase the suction pressure level to the discharge pressure level
decrease the suction pressure level to the discharge pressure level
The bearing in a motor was found to be overheated. What could be the likely cause?
Loose electrical connection
Not correctly greased with approved lubricant
Low motor current
Overload relay undersized
The purpose of a cooling tower in an air-conditioning system is to cool water by
exposing it either directly or indirectly to the ambient air
suppressing it either directly or indirectly to the ambient air
absorbing heat from ambient air and divert it into the building
dissipating heat from ambient air and divert it to the building
Calculate the Coefficient of Performance (COP) of the chiller if the cooling capacity is 2500kW and the electrical power is 500kW
5
0.2
0.5
7
In accordance to Code of Practice for Air-conditioning and Mechanical Ventilation, office requires minimum rate of outdoor air supply of 2 CMH per m2 floor area. If an office floor area is 200m2, determine the minimum amount of outdoor air required for this office.
400 CMH
200 CMH
600 CMH
800 CMH
When handling the system components of a burnt out compressor, which type of gloves should be worn?
Leather
Cotton
Plastic
Rubber
Which personal protective equipment should be worn when handling transfer of refrigerant?
Gloves and goggles
Helmet and ear plug
Goggles and helmet
Ear plug and gloves
