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Quiz 9

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Created by: Rayofsun

Question	Answer
The fun spacing recommended for chilled water air conditioning coils is	8 to 14 fins per inch
The fin spacing recommended for hot water and steam	4-14 fins per inch
The fin spacing recommended for direct expansion coils for low temperature applications such as cold storage or freezer rooms	3 to 8 fins per inch
In air conditioning systems coils with rippled fins and a staggered tube pattern	Create more turbulence and improve heat transfer efficiency
The two types of finned surfaces used on most modern air conditioning coils are	Spiral finned and continuous plate finned
The effects of using ethylene glycol in a hot water heating coil include	A lower heat transfer rate Better protection against freezing Increased friction losses in the coil and piping A requirement for a larger pump with more horsepower
What are four true statements about vacuum breakers	prevent freeze ups caused by negative pressure in coil Pipe connections of check valves used as vacuum breakers connected to return header “”of check valves used as vacuum breakers may be left open
Where must a vacuum breaker be installed in relation to the control valve	It must be installed after the control valve and as near as possible to the inlet connection to the coil
Short steam coils are not likely to freeze providing	Positive drainage of condensate is ensured
A high velocity terminal reheat system differs from a low velocity system in the	Supply air velocity Size of supply air duct Increased fan size
By keeping the supply air temperature for a low velocity terminal reheat system at 12.5 c year round this system is	High in energy consumption
In a combined air conditioning system the conditioned air supplied from the mechanical room normally provides	Cooling and ventilation
When analyzing a building for an air conditioning system the two most important considerations include	Which of the basic requirements must be provided Which requirements are desirable but not essential
In a central air conditioning system where are the thermostats located	One in each zone
In a fan coil unit with makeup air system the supply air from the central AHU to the fan coils in each room is delivered by	A low velocity duct
A room thermostat of a fan coil unit	Regulates the water control valve on the fan coil
Fan coils with a makeup air system utilize a central system to provide	100 percent fresh air and humidity control
The similarity between the constant air volume system with perimeter heating and a variable air volume system with perimeter heating is that the supply air is controlled at	12.5 c
Among the various types of heat pumps the simplest most practical and most desirable is the	Water to water type using a well as the heat source
The term coefficient of performance is used for rating	Heat pumps
By tilting the evaporator section of a heat pipe recovery unit below the horizontal the heat recovery rate of the system will be	Increased
The heat recovery rate of a thermal wheel can be improved by	Reducing the speed of wheel rotation
For a small HVAC system employing a refrigeration compression unit the simplest control would be	To cycle the compressor on and off
To manually reposition an air conditioning systems outside air damper the device that must be installed is	A gradual switch
Freestanding portable units used for home humidification normally have a delivery rate of	5 litres every 8 hours
The difference between a steam pan humidifier and a steam grid humidifier is that the steam pan type	Has a greater time lag in responding to a change Uses an on off or a modulating control valve Is generally used on smaller systems with lower demand
The provisions that must be followed to obtain proper performance of a hot water heating coil include	Counterflow arrangement of air and water Connection of water supply at the bottom of the coil Install air vent at the top of the coil
For normal heating applications the required number of rows for a hot water coil seldom exceeds	2 to 3 rows
One of the methods used to provide uniform steam distribution to the individual tubes of a steam coil is	Employ an orifice at the supply end of each tube
When a preheat coil is employed in an air conditioning system to prevent overheating the space temperature the mixing air temperature is limited to	18 c
The preferred steam trap for insulation on air conditioning heating coils operating at higher pressures ( in excess of 172 kPa) is the	Inverted bucket type
Steam coils with long tubes are more likely to freeze when the outside air temperature is	Mild such as-2 to -1
To prevent the freeze up of a hot water coil used in sub freezing temperatures the velocity of air passing over the coil should not exceed	3.55 m/s
An air handling system located in a single mechanical room distributes conditioned air throughout the building by means of ducts is the	Central system
A small air conditioning system with DX coils condenser compressor fans and controls all located in a closed casing that only provides air filtration cooling ventallation and dehumidification is called a	Window air conditioner
The air handling system that has its cooling coils and heating coils arranged in an offset parallel pattern	Multi zone system
The application of an air conditioning system depends on	The geographical location The type of occupancy The building layout
What are four things that a forced air system used in a residential house does	Provide natural gas heating Humidification Ventilation Cooling
Fan coil unit in a hotel or motel room provide the room with	Heating cooling and air circulation
In a constant air volume system with perimeter heating the set supply air temperature may result in over cooling in rooms if	Cooling loads are less than maximum
The property by which an induction air conditioning system gets its name is	The way the air in the room is circulated
The benefit of using a compartmental variable air volume system is	Operating flexibility allowing each floor to be operated independently
To convert a large refrigeration system into a heat pump	A reversing valve must be installed A second expansion valve must be installed Two check valves must be mounted in parallel to the expansion valve
Coefficient of performance is defined as a units	Heating output divided by the energy input
A heat recovery system that operates in sub freezing temperatures is likely to have ice formation on the	Recovery coils
The system that has little threat of preheat freeze up is the	Preheat system with face and bypass dampers
To insure good mixing of the outdoor air with the return air the dampers in the mixing plenum should be installed	Opposite each other
When referring to tubes as used in heating or cooling of air the tube surface itself is called the. Blank surface and the extended fin surface is the blank surface	Primary Secondary
What are three methods used to ensure uniform distribution of steam within the tubes of steam heated coils	Steam distributing inner tube Orifice in tubes supply end Distribution plate in header
Why is it more likely for outside air heating coils to freeze up when the outside air is slightly below freezing than when it is like -20	Because of modulating steam control valves in low temp are fully open but -2 they modulate letting in a sluggish flow that freezes easy
What sizes coils is it good to use	Ones small enough so that at least 40 percent is used
Why does the minimum steam supply pressure before the control valve should be 68 kPa or greater	To overcome pressure drops in the coil
What are four points to consider when using hot water to heat sub freezing air	Constant stream of water to the coil Air velocity through the coil should not exceed 3.55 m/s Positive air venting of the coil is essential Control system must be selected to warn if Circulating pump fails or heat source fails
What is the purpose of a “freeze stat” in the outlet of the heating coils for a hot water system	It is a safety control which will stop the fan and close the outside dampers in the event that the t4 should malfunction
State the purpose of a flow switch in the outlet of the heating coils for a hot water system	Or sail switch it is another safety control. It will stop the fan and close the outside dampers if the flow of water is interrupted due to pump failure or the failure of hand valves
Explain why ethylene glycol should not be heated in a boiler	Because the heat transfer surface shouldn’t exceed 140 c if it does it will cause a breakdown of the inhibitors
What is the proper way to heat ethylene glycol	Through a heat exchanger using steam as the main source of heat also called a steam glycol converter
What are three recommendations that must be followed in steam heating systems	Tubes must be in a vertical position to ensure condensate drainage When not in a vertical position coils must be sufficiently pitched to allow proper condensate drainage Make sure that the coils are completely stainable when system is switched off
What are six recommendations for piping handling systems	Support piping independently of coils Provide swing joints of all flexible fittings Pitch the condensate 21mm per 1/4 inch per foot No modifying or adding coil extensions Use pipe size at the inlet and outlet of the steam trap
What is the proper pitch for steam condensate return lines?	10mm per 1/8 inch
Five t recommendations for installing steam traps in steam heating systems	Selection based on pressure difference across trap minimum capacity = to 3 x coil condensation rate Location 12 inch below coil return Trap each coil separately Float and thermostat F and T preferred Inverted bucket trap pressure 172 kPa +
What are the three last recommendations for the installing of steam traps	Overhead returns require 7 kPa of available pressure at the trap discharge Install strainer near inlet of each trap Use same pipe size for drip leg as the rest of the system
A single control valve Blank Blank Blank Blank Blank Blank Blank Blank connected in parallel since each coil has equal loading and pressure drop	May be used on a bank of coils
List the seven functions of a building air conditioning system	Heating Cooling Ventilation Humidification Dehumidification Air circulation Filtration
List the three basic different air conditioning systems	Unitary each individual room has a self contained unit Central air comes from a central mechanical room air distributed through air ducts Combined systems. Air control in a central room that supplies ventilation and cooling other ind equipment
Define “free cooling”	This involves modulating dampers that a just to the outdoor temperature. When the outdoor temperature is between 12.5 to 24 c they are fully open and are subjected to some cooling Above 24 they move to 10-15 percent
How is temperature control of window air conditioner is achieved	A thermostat with a sensing bulb located in the return air flow to the evaporator coil starts and stops the compressor Wide swings of temperature
How does a slinger ring operate in a window air conditioner	Condensate from the evaporator coil is drained back into a pan located below the condenser and is evaporated when thrown against the condenser coil by a slinger ring on the fan
What is the difference between a window air conditioner and a packaged air conditioning unit	Packaged mounted on the floor Connected with duct work Can handle much larger areas Humidification provided Are quieter
How much cooling can roof top heating handle in comparison to packaged units	3-75 tinned Packaged 2.7 to 13.6
Single zone constant air systems are similar to rooftop except that	The air handling unit is located in a mechanical room within the building
How does a terminal reheat low velocity air conditioning system	Located central mechanical room Every zone is fed through a different branch duct A steam or hot water reheat coil is installed in each duct
What is the disadvantage of terminal reheat low velocity systems	Very high energy consumption Is designed for a maximum cooling load
Describe the operation of a multi zone air conditioning system	From 2-12 zone mixing dampers are located at the discharge of the unit Each pair is connected by a separate duct to each zone A space thermostat in the zone acts to adjust the mix of hot and cold air Dampers are linked so full opening of the cold
What are five combined air systems	Constant volume system with perimeter heating Fan coil system Hydronic heat pump system Variable air volume w perimeter heating system Compartmental variable air volume system
What is unique about the constant volume system with perimeter heating	Room thermostats regulate temperatures Wall fin radiators located against exterior walls Low velocity duct work Operates at constant volume Heating is supplied under windows Hot water is supplied by a boiler
What are constant volume system with perimeter heating used primarily for?	Multi zone buildings and schools
What is the negative about constant volume system with perimeter heating	Not well suited for larger buildings due to the space requirement
What is special about the fan coil system	Located in the exterior wall or in the ceiling 100 percent outdoor system Temperature is controlled by a wall thermostat Boilers and chillers located in the boiler room 2 pipe arrangement return and supply
What is special about a hydronic heat pump system	Consists of a central hydronic heat pump with central makeup air system 1-5 tonnages of cooling Units are installed false ceiling space one unit zone 100 percent outside air system Provides ventilation humidity control heating cooling coil
What are the advantages of the hydronic heat pump system	Good multi zone control capability Reduced mechanical space requirements Low energy consumption
What is bad about a hydronic heat system	High electrical consumption Stop start compressor may result in temperature swings Compressor noise
What is so special about the variable air volume with perimeter heating system	Similar to constant volume but air treated diff Air supplied at constant temperature reheat by perimeter reheat coils They have a VAV variable air volume box located in each branch duct The air volume is constantly changing
What are the good and bad things about variable air volume	Good popular and energy efficient Bad controls difficult and expensive Diffusers have to be carefully selected not to dump air on occupants
What is so great about compartmental air volume system	Similar to VAV designed for larger buildings Uses smaller air systems Mechanical room contains filters cooling coil supply fan 100 percent outdoor air providing 10-15 percent Units may be located on outside wall
What is good about compartmental variable air volume What is bad about the “”	Occupancy is only one floor If one component breaks down the entire system is shutdown Units are not capable of free cooling
Describe the run around system used for heat recovery in air conditioning systems	Consists of two fin-tube heat exchangers coils coupled together by a circulation system in which liquid is pumped One coil is installed in the exhaust duct work The other one is installed where air is introduced into the building
How does one fix the problem of freezing and ice formation of the exhaust system during cold weather and the glycol dropping below freezing	Coils are limited to 6-8 rows Install a three way mixing valve When temperature reaches-3 some the warm liquid will be diverted back to the recovery coil
What are the advantages of a run around system	Good no contamination occurs if exhaust and ventilation System adaptable to retrofit applications Installation cost is cheap Doesn’t take up much space Maintenance is simple
What is the disadvantage of a run around system	Recovery range is 45-55 percent low for an HVAC system Temperature difference must be large between 25-45 percent in order for the system to be efficient
What is a heat recovery wheel	Rotary regenerative heat exchanger Has a single exchange unit mass of material services as a heat carrier Has a casing split into two sections a rotating wheel Wheel is divided into sections each section filled with suitable heat transfer material
What sort of heat transfer material does thermal wheels use	Corrugated knitted aluminum Alumized steel wire
Advantages of thermal wheels	Piping and plumbing not required Small motor Good recovery for sensible heat 60-70 percent Latent heat 20-50 percent
Disadvantages of the thermal wheel	Side by side duct work required Large space required Cross contamination possible Perfect sealing is impossible
In a thermal wheel direction of the exchange depends on the blank	Season
How do you generate max transfer efficiency in a thermal wheel	Two air streams must work in opposite directions
What is a heat pipe recovery system	It is a tube with a capillary wick consisting of fine circumferential striation machined into its surface Tube is permanently sealed at both ends and filled with refrigerant
How does a heat pipe recovery system work	Warm air flows over one end of the pipe transferring the heat and causing the refrigerant to vapourized Vapour flows back to the cold end of the pipe and condenses The condensed liquid is entrained by the capillary action of the wick
What are three types of how to apply heat recovery processes	Process to process Process to comfort Comfort to comfort
What are the advantages of heat pipe and recovery units	Piping and pumps not required No continuously moving parts Recovery is practical for a wide range of temperature from -50 to 700 No cross contamination No external power needed Wide variety of sizes that makes them adaptable to many spaces
Disadvantages of the heat pipe recovery system	More expensive than the runaround system
What is the main advantage of using a heat pump over a more conventional air conditioning system	The heat pump produces three times the heat of a conventional heater
What are the disadvantages of using a heat pump over a conventional heater	Initial cost is higher Efficiency drops off rapidly when outside temperature is lower so basically when they are needed the most
What are three types of heat pumps	Water to air Water to water Earth to air
What are 5 methods of regulating air heating in heating an air conditioning system	Direct modulation of the control valve By modulating the position of the three way valve on the hot cold line of the heating coil By changing positions of the dampers to change the flow across the heating coil By modulating the actuators on steam
What is the purpose of a static pressure damper in a variable volume system	The purpose is to control the static pressure in a system It measures the pressure in the supply duct in response this control modulates the damper on the fan
Steam distributing heating coils	Distribute steam evenly over the entire coil
Fin surface area of a heating or cooling coil is called	Secondary surface area
Flat finned surface type coils are normally used for	Low temperature applications where ice may form
Rippled-finned surface type heating coils	Increase the heat transfer efficiency by creating more turbulence at fin surfaces
To assure air is properly vented from a heating or cooling coil	Supply water connection should be at the bottom of the coil
The face velocity of a heating or cooling coil is the	Average velocity of the air flowing over the face area of the fin surface
With the counterflow arrangement of air and water in a cooling or heating coil	The water supply connection is on the same side as the air leaving the coil
What is a limiting factor for the fin spacing of a HVAC coil	Resistance to airflow
What are four true statements about water filled heating or cooling coils	Coils should be hooked up in a counterflow arrangement The bottom connection should always be the water inlet Adequate air velocity over the finned surface must be maintained Coils need to be able to vent air
Finned tube coils in air handling systems are often called	Extended surface coils
The most vital element to ensure effective heat transfer in a fin-type heat exchanger coil used for HVAC service	A good bond must exist between the tube and fin
What are four true statements about coil surfaces	Finned coils less expensive than smooth coils of same heat transfer capacity Finned coils more compact than smooth tube coils of the same heat transfer capacity Fins increase contact surface area between air stream and tubes Air flows between fins
What are four causes of freezing in hot water coils	Failure of the circulating pump Very low circulating water velocity Failure of the heat source Poor air venting of the coil
What are four true statements about vacuum breakers	used to prevent freeze ups caused by negative pressure in steam heating coils Check valves used as vacuum breakers may be left open to the atmosphere and may be connected to the condensate return header They are essential for functioning steam traps
Steam coils with a short tube length of 1.1 m or less in comparison to steam coils with long tube lengths	Are less likely to freeze if the steam trap is properly chosen and the coil is properly piped
What are four true statements about glycol preheat system using hot water as its heat source	Flanges,manual shutoff valves must provided facilitaremoval of heat exchanger coil Temperature controller opens hot water supply valve when temperature outside10 c Hot water flow switch prevents glycol pump starting until water supply valve established
Ethylene glycol used in glycol coils	Has a lower heat transfer efficiency than hot water
In steam coils with long tube lengths and heating large amounts of low temperature outside air freezing problems are minimized by using	Preheat coils controlled by an outdoor temperature controller
Glycol coils using ethylene glycol	Are not recommended for use in heating and air conditioning systems in the food industry
To prevent freezing of the steam coil when steam pressure at the coil inlet is too low or is lost	Provisions are made to stop the fan and close the outside air dampers
Steam coil piping and trapping	Handle more types of fluids than hot water and glycol coils
What are four things in respect to steam trap installations that are advisable	Install a strainer near the inlet of each trap Drip the steam supply main through a steam trap into the condensate main Each steam coil requires its own dedicated steam trap Choose a steam trap based on the pressure differential across the trap
The flow arrangement best suited for hot water coils used to heat sub-freezing air is	The parallel flow arrangement because it gives better protection against freezing
Which steam trap is preferred to use with steam coils operating at low and medium steam pressure	Float and thermostatic trap
The inverted bucket steam trap as applied to steam heating coils is used when the coil steam pressure is	Higher than 172 kPa or 25 psig
It is good design practice to select a steam coil size so that	At least 40 percent of the coil capacity is needed when the air temperature entering the coil is -1 c
With respect to heating coils air vents are not required when at the steam coil	If a float and thermostat trap is used at the steam coil provided the condensate return lines are under atmospheric pressure and the steam main is adequately vented
When air handling units use hot water heating coils energy can be saved by	Adjusting the water temperature set point according to the outside air temperature
What air handling system is not appropriate for a single zone application	Dual duct system
Which air handling system is not suitable for providing cooling simultaneously to several distinct locations in a building	Roof top unit
The terminal reheat air handling system has very high energy consumption because	It coils the air for solar radiation heated zones and then reheats the air for the remaining zones
The provision of outside air into a building does these four things	Provide make up Replenish oxygen Remove odours Ventilate the building
What are four true statements about central air conditioning systems	major equipment central systems located in a central mechanical room Air is conditioned in main mechanical room and distributed by duct work The central system is able to utilize large central equipment with high efficiency Used in large buildings
Four true statements about unit ventilators	Used in areas with limited floor space Ind room temperature control Provides heating or cooling Room air mixed with outside air
Buildings require heat sources to	Offset the buildings heat losses
Free cooling in regard to the HVAC system operation refers to	Manipulating mixed air dampers in cooler days to eliminate the need for mechanical cooling
What are four characteristics of a dual duct system	Provides constant volume air circulation rate in each zone Provides good control of space conditions Handle more zones than a multi zone system Easier to modify than a multi zone system
Locating HVAC equipment in mechanical rooms is preferred	So that maintenance may be preformed without disturbing occupants
A system used extensively in hotels and motels due to its minimum space requirement relatively low initial cost and high degree of individual zone control is called	A fan coil unit with makeup air system
What are four statements for induction HVAC system	Ratio of secondary to primary air is 4 to 1 Room thermostat modulates flow of chilled or hot water to the unit coil Primary air can be heated proportionally to outside air temperature 2 pipe temperature is difficult during shoulder season
What are four true statements about hydronic heat pump HVAC systems	Unit discharges heat to the water piping system during cooling mode Water temperature must be 15-32 No pipe insulation needed since temperature above dew point System can be thermally self balancing
What are four true statements about two-pipe arrangement	The arrangement is the least costly Piping is connected to the boiler during winter and chiller during summer The arrangement is made up of a supply and return connection to a single coil
Four advantages of a combined HVAC system over a central air system	Usually requires less building space for mechanical equipment duct work More efficient in operation Zones not needed can be shut or temperature regulated differently Additional cooling can be provided to zones that receive heat from solar radiation
While addressing the building function factors of an HVAC system a designer considers	Normal occupancy periods
What are four true statements about variable air volume system with perimeter heating	Air is supplied at 12.5 c Room temperature is controlled by the volume of air supplied Air is distributed via low or medium duct work Zone air supply is modulated by a vav box
What are four true statements about fan coil units with make-up air systems	Used extensively in motels and hotels Minimum space requirements Provide heating cooling filtration and air circulation High degree of individual zone control
An HVAC system that uses high pressure induction system utilizes. Blank blank blank to provide room air circulation	A nozzle arrangement
A common complaint against the fan coil with makeup air system is	The fan noise is excessive
An HVAC system that provides cooling and heating all year round is highly efficient but has a high initial cost. The system consists of two separate supply and return piping systems that are connected to separate coils	Four pipe system
The run around coil heat recovery system uses a. Blank coil in the inlet air duct and a blank coil in the exhaust air duct	Preconditioning Recovery
What is the disadvantage of heat pipe heat recovery systems?	A side by side duct arrangement is needed
A system consists of two finned tube heat exchangers Where is the preconditioning coil of this system located	In the duct work handling outside air
The recovery system which makes use of an underground heat exchange coil is called a	Heat pump
When is the capacity of a heat pipe at a maximum	When the evaporator is lowered below the horizontal
A refrigeration system used in HVAC service that can provide both heating and cooling is a	Heat pump
A variable air volume HVAC system requires static pressure control on the. Blank air duct system	Supply
In an HVAC system to provide a two position damper with manual proportional control a blank is required	Gradual switch
Why is the positioned for the outdoor air damper of an HVAC air handling unit interlocked with the supply fan	So the damper will open when the fan starts
In an HVAC system a differential pressure controller maintains supply air duct static pressure constant by	Modulating the damper on the suction side of the fan
The outdoor air inlet damper of an HVAC air handling unit may be split into two parts to provide	Minimum outside air required for ventilation during times of maximum return air circulation
In an HVAC air handling unit temperature control that uses face and bypass dampers	Closes the bypass damper and opens the face damper to direct air through the coil
What should be done to prevent the compressor in a cooling system from starting and stopping too frequently	Run the compressor continuously and unload it when the temperature set point is reached
When the outdoor air damper of an HVAC system opens to increase the flow of fresh air the return damper	Closes to reduce the recirculated air
HVAC control system maintains minimum. Blank. Air during periods of extreme high and low ambient temperature	Ventilation
In refrigeration systems the most common methods used to control the capacity of a reciprocating compressor are	Intermittent operation and continuous operation
The temperature in the evaporator depends	On the pressure in the evaporator
What are four things that a economizer of a packaged water chiller does	Have an intercooling effect on the compressor Reduce the power required for compression of the refrigerant Reduce flash vapour in evaporator Increase refrigerant capacity of a system
The refrigeration compressors operating control that uses a bimetal element is a	Flow switch
The liquid line shutoff valve of a refrigerant system is	Closed when charging the system with liquid
The safety control of a centrifugal compressor that ensures the compressor only starts under a no load condition is called the	Vane closed switch
Name four steps that are part of the start up procedure of a centrifugal compressor refrigerating system	Operate the oil pump for at least 10 minutes before starting the compressor Open the stop valves in the chilled water system Open the makeup water valve Check the refrigerant levels
The funds allocated for the selection of a buildings HVAC system would be found in the Blank Blank portion of the construction budget	Capital cost
When a chiller has stopped due to low water temperature the chilled water temperature subsequently rises 5-6 c above the chilled water temperature set point the	Compressor will start
During seasonal startup when should the purge pump be started	About one half hour after the absorption unit is started
In a refrigeration system what are four causes of poor condenser performance	Waterside scale accumulation Oil film accumulation on the inside of the condenser Accumulations of non-condensable gases in the condenser Inadequate coolant circulation
What is a pressurestat and what can it not be used in conjunction with?	Automatic expansion valve
What is a true statement about flow switches	They can only be used with liquid not air
What are four components of mechanical purging systems for lithium bromide chiller	Purge pickup tube Purge chamber Oil trap Vacuum pump
Biological fouling in recirculating cooling water towers is caused by algae. Blank and bacterial growth	Fungi
Parallel blade air dampers when used in HVAC systems	Are often used on mixing boxes for both outside and recirculated air
What are four common types of refrigeration condensers	Air-cooled Shell and tube Shell and coil Double tube
Evaporator bypass dampers require. Blank to move	Actuators
In the lithium bromide refrigeration system what is the function of the concentrator	To increase the absorbency potential of used absorbent
In a refrigeration system controlled by a high pressure float valve excessive refrigerant charge will cause	Liquid carryover to the compressor
What are four functions of a refrigeration compressor	Raises pressure of refrigerant Raises temperature of the refrigerant Maintains a low pressure in the evaporator Circulates refrigerant through the system
The automatic expansion valve in a refrigeration system operates on the principle of balancing	Evaporator pressure against a return spring
Multi zone air handling system when the hot deck is fully closed	The cold deck is fully open
Backwards inclined airfoil fans	High capacity high pressure
All refrigeration evaporators	Boil liquid refrigerant at low pressure low temperature
The principle cause of steel corrosion in cooling towers is	Dissolved oxygen
With regard to fan capacity control which of the following has a declutching feature	A fluid drive
An entire centrifugal compressors refrigerating system including auxiliary equipment can be stopped by simply pressing a button unless	The systems auxiliary equipment is not electronically interlocked
What are four true statements about lithium bromide absorption refrigeration systems	Lithium bromide solution has the ability to absorb water vapour readily The system efficiency is increased by forcing water through a spray header Evacuating system lowers the boiling point of water The operating cycle in the system is continuous
What are four true statements about automatic expansion valves	maintains constant pressure in evaporator during compressor operation regardless of load A spring exerting downward force on diaphragm opens it spring force is counter acted by evaporator pressure When compressor stops valve automatically shuts off
The vane axial flow fan	Has less spiral air flow less friction and better efficiency than the tube axial fan
What is not likely to be found in a typical constant air volume system when combined with perimeter heat	Heating coils
In a mechanical air intake natural exhaust ventallation system the pressure in the building is	Slightly above atmospheric pressure
What type of units discharge heat to the water piping during the cooling mode	Hydronic heat pump
Electrical starters and contractors should be inspected	Annually
With all other factors being equal a counterflow cooling tower. Blank as a cross flow cooling tower	Requires less floor space
The chilled water flow switch prevents the	Refrigeration compressor from starting if chilled water flow has not been established
Calculations of supply air duct leakage loss include	10 percent leakage loss when the supply air duct is outside the conditioned space
During summer the effective temperature is	19 and 24
In the lithium bromide refrigeration system what is the function of the concentrator	To increase the absorbency potential of used absorbent
In a refrigeration system controlled by a high pressure float valve insufficient refrigeration charge will cause	Starving of the evaporator and reduced cooling capacity
What are four true statements about shell and tube refrigeration evaporator	Known as a chiller Refrigerant contained in the shell and surrounds the tubes Refrigerant vapour is drawn out of the evaporator by the compressor It cools many liquids
A compressor system can be divided into two parts A high pressure section carrying the head pressure and a low pressure section carrying the	Suction pressure
In an ammonia absorption refrigeration system the. Blank ammonia is absorbed by the. Blank aqua	Vapourized Weak
B 52 refrigerant discharge from a pressure relief device to the atmosphere shall not be less. Blank. From any window ventilation opening	7.6 m
Raising the condescending point of the refrigerant vapour above the temperature of the cooling medium is the function of the	Compressor