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Technician interview Answers:
What does The CHILLER do?
Chiller is used to generate ice water . It Can be used for example to provide air conditioning in buildings and cooling of machines
Why use chiller?
- a) In large buildings, the cold generation is centralized in a single point.
- b) By concentrating the generation of cold, the need for a large number of air conditioning equipment is avoided.
- c) The need for electrical and power connections throughout the building is avoided.
- d) Having less equipment reduces the chances of failure.
- e) Excess ducts are avoided throughout all the premises.
- f) The distribution of the low temperature is carried out by means of pipe networks that carry the ice water to all the premises of the building.
- g) If the selection of the chiller is adequate, it can generate quite interesting efficiency values.
How is the traditional chiler?
The traditional chiller consists of a compression refrigeration circuit with the four basic components, plus the water distribution:
- a) evaporator.
- b) condenser.
- c) compressor.
- d) expansion device.
- e) Water distribution system.
How does the chiller work internally?
- a) The refrigerant inside the refrigeration circuit passes through the evaporator, where it is at low pressure and low temperature, in this way it can cool and generate ice water.
- b) The ice water passes through the evaporator, to cool down, but never mixes with the refrigeration circuit.
- c) The ice water is directed to the building, and cools the premises.
- d) The refrigerant inside the refrigeration circuit, leaves the evaporator with the heat that was removed from the ice water, and enters the compressor.
- e) The refrigerant gets pressure in the compressor, to be taken to the condenser.
- f) In the condenser, the heat that was removed to the ice water is lost.
- g) The refrigerant passes through the expansion device, to lower its pressure and become cold again.
- h) The refrigerant enters the evaporator and the cycle is repeated.
What are the types of chillers?
By the type of condenser cooling, we can classify them into:
- a) chiller with air-cooled condenser.
- b) chiller with condenser cooled with fresh water.
How does the air cooled chiller work?
- a) The traditional chiller has a compression refrigeration circuit, where the heat needs to be dissipated in the condenser.
- b) When the chiller is air cooled, powerful fans are needed in the condenser to help release the heat, which was removed to the ice water.
How does the water-cooled chiller work?
- a) The traditional chiller has a compression refrigeration circuit, where the heat from the condenser needs to be dissipated.
- b) When the chiller is cooled by water, an additional fresh water circuit is needed, passing through the condenser, to help release the heat, which was removed from the ice water.
- c) In these equipments there are two totally different water circuits.
- d) There is an ice water circuit to cool the premises of the building, and a fresh water circuit to cool the chiller condenser.
Where are the air conditioning chillers located?
The chiller can be located in the basement, or up on the roof of the building.
How is ice water produced?
- a) the ice water is produced in the evaporator of the refrigeration circuit.
- b) Usually the ice water leaves the chiller at a temperature of 7 degrees Celsius.
What function Do the ice water has on buildings?
- a) A centrifugal type pump sends the ice water around the building.
- b) Chilled water enters the air handling units, to cool the air of the premises with in the building.
What function Do air handling unit has?
- a) They are responsible by means of coils, to remove the heat from the air inside the building, using the ice water from the chillers.
- b) The management unit totally conditions the air, mixes it, moistens or dehumidifies it and adapts it to the needs within the building.
How is the air cooled in the air handler unit?
- a) The chilled water from the chiller is passed through coils, through which the air flows that need to be cooled pass.
- b) Water enters the amu at a temperature of 7 degrees Celsius, 44 Fahrenheit and exits at 12 degrees, 54 Fahrenheit.
- c) Meanwhile the air notably lowers its temperature, thereby air conditioning the building.
What do you do with the ice water coming out of the air handler unit?
- a) When the ice water leaves the air handling unit, it comes out with a higher temperature, a product of the cooling carried out in the air, usually 12 degrees Celsius, 54 Fahrenheit.
- b) the water should be brought back to the chiller to cool down again, and brought back to 7 degrees Celsius, 44 Fahrenheit.
What happens to the ice water again when it comes out of the chiller?
- a) When the water comes out of the chiller, it will have given up the heat gained in the air handling unit.
- b) The ice water will return to 7 degrees Celsius, 44 Fahrenheit.
How is the working cycle of the chilled water in the chiller installation?
- a) The cycle repeats and repeats, the water comes out of the chiller at 7 degrees Celsius, 44 Fahrenheit.
- b) The water is directed to the air handler unit and gains 5 degrees Celsius, 10 Fahrenheit
- c) The water returns to the chiler at 12 degrees Celsius, 54 Fahrenheit
- d) the water comes out of the chiller again at 7 degrees Celsius, 44 Fahrenheit.
Why is the water coming out again at 7 degrees Celsius, 44 Fahrenheit?
- a) The heat from the ice water reaches the chiller.
- b) The ice water now has a temperature of 12 degrees. centigrade, 54 Fahrenheit.
- c) The heat from the water is delivered to the refrigerant in the cooling circuit in the chiller.
- d) the heat of the refrigerant leaves the latter circuit, through the condenser of the chiller refrigeration circuit.
What does the heat received in the condenser of a water-cooled chiller do?
- a) The heat from the condenser is sent to another water circuit at room temperature.
- b) Water at room or cool temperature belongs to a totally different circuit, to the ice water circuit.
- c) The new heat exchange with the new water circuit, we will call it the exchange of the fresh water circuit.
How does the fresh water circuit of the water cooled chiller condenser work?
- a) There is a new centrifugal pump station, which we will call cooling tower pumps.
- c) The water is carried through the circuit, towards the cooling tower.
What is a cooling tower?
- a) The cooling tower is the point where air from the outside environment is forced into the tower.
- b) The tower uses a powerful internally located fan.
- c) The air inside the tower dissipates and rejects the heat of the water that has just cooled the condenser.
How many exchanges do we have, in the installation with chiller cooled with fresh water?
we have four heat exchanges.
- a) heat exchange of the chilled water with the internal air of the premises, to cool the air of the building.
- b) Heat exchange of the refrigerant within the refrigeration circuit, to generate the ice water.
- c) heat exchange of the refrigerant of the refrigeration circuit, with the fresh water circuit, to send the heat of the condenser refrigerant to the environment.
- d) Heat exchange of the fresh water, with the outside air, to cool the fresh water.
What happens to the fresh water in the cooling tower circuit?
- a) Fresh water reaches the chiller condenser at a temperature of 30 degrees Celsius, 86 Fahrenheit.
- b) The cool water takes the heat away from the condenser, and goes from 30 to 35 degrees Celsius, 86 to 96 Fahrenheit.
- c) Through a system of pumps, fresh water is taken to the cooling tower.
- d) Fresh water loses heat in the cooling tower, and goes from 35 to 30 degrees Celsius. 96 to 86 Fahrenheit.
- e) Fresh water at 30 degrees centigrade is directed back to the chiler condenser. 86 Fahrenheit.
What are the causes of lower than normal chiller suction pressure?
- Lack of refrigerant.
- Too many compressors on, in the case of chillers with several compressors.
- Lack of cleaning of the chiller evaporator.
- Lack of chilled water flow through the chiller evaporator.
- Failure of temperature sensors.
- Expansion valve failure.
Excess discharge pressure in the chiller?
- Lack of cleanliness in the condenser.
- Failure in fans in air cooled chiller.
- Lack of water from the cooling tower, in case of water cooled chiller.
- Excess of thermal load.
- Lack of compressors on, in case of chiller with several compressors.
- Lack of insulation in suction piping.
- Excess of refrigerant.
What is the cause of a lower than normal return chilled water temperature?
- Lack of thermal load in the application.
- Dirty heat exchangers, such as fan coil or air handler exchangers.
- Failure of air handling unit fans or fan coils.
- Dirty air filters in air handling unit or fan coils.
- Wrong control strategies, regarding number of chillers, or number of compressors on.
How is an efficient chiller?
It is a system that has the capacity to generate only the cooling required by the application. It is characterized by having a high value of the parameter I P L V high.
What are the chillers that exist, according to the temperature of the chilled water they generate?
- Conventional chillers, generally for air conditioning applications, with water temperatures of 44°F or 7°C.
- Chiller in industrial refrigeration applications, for medium-low temperature: For chilled water temperature values between +20°F and +35°F.
- Chiller in low temperature industrial refrigeration applications: Generally, to generate chilled water between +20°F and -59°F.
- Chiller in Ultra-low temperature industrial refrigeration applications: To generate water between -60°F and -112°F.
How can chillers be classified according to their cooling capacity?
- Low Capacity Chiller with less than 50 KW cooling capacity.
- Medium Cooling Capacity Chiller, with cooling capacity between 50 and 200 KW.
- High Cooling Capacity Chiller, with a cooling capacity greater than 200 KW.
What are the possible combinations between compressor and condenser in chillers?
- Chiller with air-cooled piston compressor.
- Chiller with water-cooled piston compressor.
- Chiller with air-cooled scroll compressor.
- Chiller with water-cooled scroll compressor.
- Chiller with air-cooled screw compressor.
- Chiller with water-cooled screw compressor.
- Chiller with water-cooled centrifugal compressor.
What are the most important conditions that must be known for the correct selection of a chiller?
- Minimum temperature value and required chilled water flow rate.
- With the minimum temperature value, you must classify the type of chiller you need.
- To know the return water temperature values for each process or machine to be cooled.
- Make a balance of supply and return flows, to know the capacity of the chiller that is needed, so as not to oversize the equipment.
- To know the water treatment required by the installation.
What special treatment does the water of an industrial chiller have?
- The purpose of the chiller water treatment is:
- Control corrosion.
- Prevent bacteria growth.
- Prevent water freezing
What is the best-selling type of chiller in the world?
The water-cooled condensing chiller with screw compressor, with more than 200 KW of power, is one of the most commercialized chillers in the world
Which chiller requires very little maintenance?
The scroll compressor chiller with air-cooled condenser is characterized by low maintenance requirements.
What is the most common application sector for chillers?
Undoubtedly the air conditioning sector, in commercial applications.
What are the most frequently recommended refrigerants for low-capacity chillers for air conditioning?
Refrigerant gas R-410A, R-407C, R-32, R-454B, R-452B.
What are the most frequently recommended refrigerants currently used in medium capacity chillers for air conditioning?
Refrigerant gas R134a, R-450A, R-513A, R-1234yf, R-1234ze (E)
What are the most frequently recommended refrigerants currently used in large capacity air conditioning chillers?
R-1233zd (E) R-1336mzz (Z)
What is the most popular low pressure refrigerant in chillers?
What is the best known medium pressure refrigerant in chillers?
R-134a, R-513A, R-1234ze, R-515B, R-1234yf.
What is the best known high pressure refrigerant in chillers?
R-410A, R-454B, R-452B, R-32.
Chiller Operator Plant interview Questions:
What function do the primary pumps have in the chilled water plant?
Deliver the water to the evaporator of the chiller, for its cooling.
What function do the secondary pumps have in the chilled water plant?
Deliver the ice water to the place where cooling is needed.
Do all chilled water plants have secondary and primary pumps?
No, in fact the trend is to eliminate the secondary pump, and only work with the primary pump.
What other type of pump can exist in chilled water plants?
When the chiller’s condenser is water-cooled, pumps are needed to deliver the water to the condenser and cooling tower.
Why does the frequency inverter in the chilled water plant pumps generate energy savings?
Because at times when less chilled water is needed, only the necessary flow can be sent.
How do you get the chilled water plant pump to control the water flow? Through the frequency inverter, changing the speed of the water pump motor.
What variable controls the amount of chilled water needed by the pipeline distribution?
Often through pressure.
Why does the pressure indicate the amount of water required in the chilled water plant?
In air conditioning applications, when a site does not need chilled water, its control valve must be closed, causing an increase in pressure in the network.
Which circuit of the chilled water plant has more problems?
The water circuit that cools the chiller condenser, because this circuit is open to the environment.
What is the function of the expansion tank in the piping network of the chilled water plant?
Absorb pressure changes in the network produced by changes in water temperature.
HVAC Interview Questions
What does HVAC mean?
Heating, Ventilation, Air conditioning.
what is the main local heating system?
A natural gas furnace, called a central heating system, uses a blower motor and air ducts to distribute hot air through vents.
Can the chiller be used for heating?
the chiller can be used for heating, when it has the possibility of working as a heat pump
How is heat pump efficiency measured?
The efficiency of the heat pump can be measured with the parameter COP
What is the typical value of the cop of a heat pump?
A heat pump that has a COP of three can create three kW of heat for every kW of electricity.
What is the most efficient heating system?
In general, ovens are the most efficient of the heating systems,
What factors should be taken into account in the design of air conditioning duct systems?
- Design speed.
- Air flows according to thermal load.
- Pressure requirements.
- Renewal rates.
- Number of supply and return grilles.
What is the easiest method to design air conditioning duct systems?
Design taking into account only the noise level and the speed of the air inside the ducts. This method does not guarantee the required flows in installations greater than 24 feet.
How much air does a room that receives air conditioning need?
On average 400 cfm for each ton of refrigeration
What is the advantage of ducted air conditioning compared to mini-split?
- Ducted air conditioning system can supply larger thermal loads.
- With the ducted air conditioning system, cold generation can be centralized at a single point.
- With the ducted air conditioning system, the amount of renewal air in each room can be controlled automatically.
- In the ducted air conditioning system, supply air flow purification equipment can be installed.
What is the natural replacement for equipment that works with R410A refrigerant?
Systems that work with R-32 refrigerant are replacing equipment that worked with R410A
What is the most frequent replacement of R22 in the same air conditioning system?
When is R417A refrigerant used?
It is used in medium and high temperature evaporator systems to replace R-22 refrigerant gas.
What is the use of R-452A refrigerant?
Direct substitute for refrigerant R-404A and R-507 in installations that may have years of use. It is also used as a replacement and in new transport refrigeration equipment.
What is the main use of R-407A refrigerant?
R407A is a substitute for R22 and R404A in existing equipment.
What should be done when changing from R-22 to R-407A?
Change the mineral oil for POE type oil, and change the filter dryer.
When is R449A refrigerant used?
The r449A is used in new equipment and as a replacement for the refrigerant gas r404A and R507 in existing equipment.
What does the acronym GWP mean?
The global warming potential, abbreviated as GWP, is used to describe the power of a greenhouse gas, taking into account how long it remains active in the atmosphere.
HVAC Certification Practice Test
We have prepared four tests with automatic qualification specialized in HVAC
|Type of Test for HVAC
|Knowledge test in heating systems
|Test of basic knowledge in ventilation systems
|Knowledge test on individual air conditioning equipment and ducted systems
|Knowledge test on chilled water plants and chillers