Pre-Test #3 Flashcards
The capacity of an evaporative condenser depends on what entering air temperature?
a) dry bulb
b) wet bulb
c) warm
d) differential
b) wet bulb
An expansion valve set for high superheat will cause
a) flooded evap
b) starved evap
c) high back pressure
d) high head pressure
b) starvation
What factors determine the size of an expansion tank?
a) amount of space the water must expand to
b) amt of air in system
c) operating pressure
a)
To check speeds or rotary equipment, which instrument is used?
a) tachometer
b) psychrometer
c) manometer
d) velometer
a)
What is the gross weight of a refrigerant cylinder?
a) freon plus tare
b) weight of cylinder
c) cylinder contents only
d) cylinder and line
a)
If a thermostatic expansion valve is partially feeding the coil
a) low superheat
b) no superheat
c) superheated
d) high superheat
d)
On an A/C system, low power factor to a motor will cause it to
a) not run at all
b) run slow
c) heat up
d) hum
c)
A modulation thermostat employs what to achieve its purpose
a) pressure
b) transformer
c) switch contacts
d) a potentiometer winding
d)
In a direct expansion chiller the refrigerant is on what side of the tubes?
a) on the shell
b) outside
c) inside
d) both sides
c)
Hydronic systems there are three rules need to divert air in the system to the expansion tank. What is NOT true?
a) we should be at lowest point of pressure
b) highest point of pressure
c) highest temp
d) lowest velocity
b)
IN brine systems on measuring the PH reading of the brine, what PH would represent neutrality?
a) 7
b) 10
c) 5
d) 0
a)
When there is overflowing and flood back, what control is being used to indicate this?
a) txv
b) axv
c) low side float
d) high side float
d)
Soft soldered joints on refrigeration piping which leak may be repaired by?
a) brazing
b) re-soldering
c) NEVER
c)
If you use R12 in machine designed for R22, what will happen?
a) cause copper plating
b) capacity of the machine will be greatly overloaded
c) capacity will be greatly reduced
d) no difference
c)
Piping system where several heat transfer units are returned along paths so that all circuits are practically equal lengths is known as?
a) reversed return
b) indirect
c) two pipe
d) down feed
a)
High pressure drop in the liquid line will result in?
a) increased efficiency
b) increased capacity
c) flash gas in the liquid line
d) superheat in the liquid line
c)
ON s ingle temp pneumatic control temperature system, a PRV reduces the tank pressure to maintain a main pressure of how much?
a) 10psi
b) 13psi
c) 15psi
d) 17psi
c)
When the thermo-controls are made of metal, the elements in the controls depend on the principle of?
a) specific heat of the metal
b) density of the metal
c) equal expansion of the metals
d) UN-equal expansion of the metals
d)
It is easier to burst tubes in a flooded chiller than in a dry chiller in a freeze up. True or False?
True
Freeze-up in a flooded chiller is prevented by __________ control
a) low water
b) low freon
c) suction pressure
d) overload
b)
If the float ball in a. high side float becomes full of liquid, the float will?
a) open
b) chatter
c) expand
d) close
d)
In a dry chiller , the freon is in the shell and the water is in the tubes. True or False?
False
A cold equalizing line on an expansion valve indicates what fault in the valve?
a) high superheat
b) leaking pin packing
c) low superheat
d) weak power assembly
b)
A water cooled condensing unit is running high head pressure and has water TD of 22degrees. What is the probable cause?
a) dirt condenser
b) air in system
c) too much freon
d) not enough water
d)
How much condenser water required for a 5 ton air conditioning system using tower water?
a) 15gpm
b) 10gpm
c) 30gpm
d) 8gpm
a)
What should be the max time delay between the steps of an increment start motor?
a) 15sec
b) 5sec
c) 30sec
d) 1min
b)
Electrical resistance is always measured in?
ohms
The oil safety switch is operated by?
a) oil pressure
b) sum of oilP and crankP
c) Diff between crankP and oilP
c)
Condensing temperature split = condensing temp - air inlet ___ bulb temperature?
dry
In a refrigeration system, suction line pressure drop = refrigerant pressure in the evaporator minus
a) suction pressure at compressor
b) 2psi
c) suction pressure at evaporator
d) superheat
a)
A technician finds the suction line pressure drop on a system is 4psig per 100feet of line, which would NOT be a cause?
a) clogged suction line filter
b) excessive oil in suction
c) dirty filters
d) pinched line
c)
What other component analysis in an air conditioning system besides the evaporator and condenser would indicate low refrigerant charge?
a) expansion valve
b) suction pressure
c) discharge pressure
d) any of the above
b)
Normal suction line pressure drop in a refrigeration system is estimated as
a) 2psig per 50’
b) 4psig per 100’
c) 2pig per 100’
c
A technician diagnosing a txv feels the liquid line downstream and upstream of the solenoid valve or strainer, what measurement would lead him this way?
a) high superheat
b) low superheat
c) high back pressure
d) low suction temperature
a)
Flooded feeds are different from direct expansion feeds in that they
a) are not as efficient
b) use bigger evaporators
c) allow for regurgitation of liquid freon
d) allow for recirculation of liquid freon
d)
The high side float is controlled by
a) rate of freon evaporation
b) rate of freon condensation
c) evaporator temperature
d) evaporator pressure
b)
Low side float is controlled by
a) rate of freon condensation
b) rate of freon evaporation
c) evap temperature
d) evap pressure
b)
Suggested possibilities of trouble indicated by gauge and superheat readings: low suction pressure and low superheat
a) overcharge
b) improper superheat adjustment
c) compressor undersized
d) evaporator is oil logged
d)
A reverse acting pneumatic humidistat increases the air pressure to a controlled device when humidity ________
a) increases
b) decreases
c) remains static
d) mixes
a)
When pressure difference across a cap tube increases, the flow of refrigerant _________
increases
Another name for a normally open valve that is pneumatically controlled?
a) indirect acting valve
b) diverting valve
c) reverse acting valve
d) direct acting valve
c)
By using nitrogen within the pipe during brazing
a) explosion hazard is contained
b) discolouration is prevented
c) copper oxide formation is prevented
d) exterior scale formation is minimized
c)
When using nitrogen to braze, pressure should be
a) very low
b) 50-100psig
c) 250-300psig
d) slightly below atmospheric
a)
Bullheaded tees are not acceptable in discharge lines. True or false?
True
The latent head used in changing a liquid to a gas or vapour is called the latent heat of
a) fusion
b) pressurization
c) condensation
d) evaporation
d
Speed of a belt driven compressor may be increased by?
a) increasing pulley size on motor
b) increasing pulley size on compressor
c) increasing belt dressing on pulleys
d) decreasing pulley size on motor
a)
On a horizontal shell and tube condenser using a water regulating valve, where should the valve be placed?
a) on the inlet side of the condenser
b) either side of the condenser
c) both sides of the condenser
d) on the outlet side of the condenser
d)
What happens when a capillary tube system is overcharged
a) it has a high head pressure
b) it will partially defrost
c) it will not sweat and frost back
d) it will have below normal low side pressure
a
An air compartment or chamber to which one or more ducts are connected and which forms part of either the supply or return of the system is called the
a) proscenium
b) vortex
c) plenum
d) plectrum
c)
What does wet bulb depression mean?
a) cavity in the bulb
b) wet bulb is located below the dry bulb
c) Difference in reading between the wet bulb thermometer and the dry bulb thermometer
c
What does the inner tube opening register on a pitot tube?
a) total pressure
b) velocity pressure
c) static pressure
d) total pressure minus velocity pressure
a)Wi
With what basic function of air conditioning are duct velocities most concerned?
a) air heating
b) air cooling
c) air humidity
d) air distribution
d)
Do all filters have a pressure drop?
Yes
The temperature of the refrigerant in the generator of absorption system is?
a) greater than that of the absorbent
b) less than that of the absorbent
c) same as that of the absorbent
c )
In practically all coils used for cooling air, the flow of air and water through the coil are in the __________ direction to each other
a) water flow
b) parallel
c) same
d) opposite
d)
There take off of a standard long radius 90 weld ELL is equal to
a) the diameter
b) twice the diameter
c) 1.5 times the diameter
c)
Important factor in the piping of supply and return fuel oil lines to an underground oil storage tank is that ______ _____ shall always be used
a) swing joints
b) clean pipe
c) two pipe
d) one elbow
a)
A standard 6” thread that has been properly cut will allow the fitting to hand tighten _____ times
a) 3
b) 6
c) 8
b
All branch (take-off) lines from a steam mainsail be taken from the
a) side
b) top
c) bottom
d) top or bottom
b)
Where oil fuel tanks are lower than the burner, on fuel burning equipment, it is recommended that they have what kind of piping system?
a) oversized
b) 3 pipe
c) 2 pipe
d) 1 pipe
c)
A boiler fitting and tank fitting remove air from the heating sitting to a point of low velocity and put that air in the compression tank. True or False?
True
Gas conversion burner which uses a small blower and discharges the flame horizontally into the fire box is an
a) upshot atmospheric
b) inshot atmospheric
c) upshot power burner
d) inshot power burner
d)
Pressure tanks in forced flow hot water heating systems should contain
a) water only
b) air only
c) steam only
d) water and air
d)
Steam fittings shall NOT be of what material?
a) cast iron
b) galvanized iron
c) malleable iron
d) brass
b
Purpose of a steam trap is to
a) trap and discharge to atmosphere
b) prevent discharge of steam into return and eliminate air and condensate from steam mains
c) collect air
b)
What type of boiler has water around the outside of the tubes being heated by hot gas within the tubes?
fire tube boiler
Science of heating and cooling with liquids is called?
hydronics
Purpose of a Hartford loop is to
a) prevent backing water out of a boiler
b) remove air form return line
c) allow for pipe expansion
a)
On a steam system the operation of an inverted bucket trap is based on the
a) rise and fall of a float
b) combination of steam pressure and wight of condensate
c) steam pressure drop
b)
In a forced flow hot water system, piping must be run around a beam, what is advisable?
a) drop pipe below beam
b) loop over beam only
c) install steam trap at low point
a)
low voltage controls in gas fired furnace are wired in
a) series
b) parallel
c) 8 wire
a)
On water pipes an eccentric reducer should be used on which of the following?
a) horizontal
b) brass pipes
c) vertical pipes
d) wrought iron pipes
a)
The three most common steam traps in use are the
a) float, thermostatic, impulse type
b) float, pea, impulse
c) float, thermostatic, vacuum
a)
All piping, valves, and fittings used to connect instruments to main piping, to other instruments or apparatus, is known as?
a) control piping
b) instrument piping
c) sampling piping
d) branch piping
b)
Air in oil line to burner may cause which one of the following?
a) pulsation
b) excessive fuel consumption
c) blue flame
d) dirty nozzle
a
Condensate mat be formed on fire side of a gas boiler if what condition exists?
a) not enough insulation on boiler
b) draft control not set
c) fuel-air ration incorrect
d) water temp maintained too low in the boiler
d)
An ASME pressure relief valve on a boiler is usually provided with a hand lever, its purpose is to?
a) close valve once it has opened
b) change operating pressure
c) test valve and relief of air on initial fill
c)
Open expansion tanks are open to atmosphere and located
a) anywhere in piping
b) discharge side of pump
c) suction side of pump above highest unit in system
c)
In the discussion of oil heating using a fuel pump, the number of pounds per square inch the pump pressure must drop to close the nozzle valve is
a) delivery
b) differential
c) head of oil
d) lift
b
two stage refrigeration system would be used when
a) ammonia is used
b) compression ratios high
b) comp ratio low
d) suction temp high
b
On refrigeration, what type of pipe or tubing is commonly used with ammonia?
a) iron or steel
b) iron or brass
c) copper or brass
d) any of above
a)
What control would be used on a cap tube or axv system to maintain desired temp
a) dual pressure control
b) high pressure control
c) temperature control
c)
The two basic types of evaporator are
a) finned and plate
b) prime surface and finned
c) flooded and direct expansion feed
c)
R-22 will support combustion under certain conditions
a) true
b) false
false
A refrigerant oil should maintain sufficient body to lubricate at high temperatures and yet be fluid enough to flow at low temperatures
a) true
b) false
a)
Most refrigerant oils are paraffin based. True or False?
False
Horizontal piping should
a) pitch towards compressor
b) pitch away from compressor
c) pitch in direction of flow
d) be level
c)
What type of threads are used in flare fittings?
a) nation fine
b) national course
c) u.s.s
d) stander pipe threads
a)
In a beverage cooler installation the sweet water bath is made of
a) alcohol
b) alcohol and brine
c) tap water
d) sugar solution
c)
A check valve on a multi-temperature system is located where and in what line?
a) coldest unit section
b) warmest unit section
c) either A or B
d) liquid line
a)
In a dry or flooded chiller of the same capacity, which one has the largest refrigerant charge?
a) flooded
b) dry
a)
A suction pressure regulator can not be used to regulate evaporator pressure. True or False?
False
A refrigerant in mechanical refrigeration systems produces its greatest cooling effect
a) through evaporation
b) by condensing
c) by compression
d) superheating
a)
A vale in the liquid line that is usually located immediately outside the condenser or receiver is known as a
a) liquid shut off
b) discharge shut off
c) receiver shut off
d) suction shut off
a)
The term induced draft could refer to
a) a type control
b) a type of compressor
c) a type of cooling tower
d) a type of diagram
c
Temp of the air surround an object is
a) wet bulb
b) dry bulb
c) condensing
d) ambient
d)
Where is the liquid receiver usually located in a cap tube system?
a) there is none
b) in the cooling coil
c) outlet of the condenser
d) suction line
a)
What may result if the compressor cylinder head gasket is too thick?
a) knocking sound
b) decrease in volumetric efficiency
c) oil pumping by compressor
d) no pumping
b)
Where is a metering type two-temp valve usually used?
a) small td required
b) large td required
c) multiple system
d) only on display case
b)
On a pressure controller, which bellows controls the low pressure switch?
a) small bellows
b) large bellows
c) neither bellows
d) both
b)
In a refrigeration system, a solenoid valve is open when the
a) power is on
b) power is off
c) valve is under pressure
d) valve is not under pressure
a)
Gauge manifold contains two shut-offs and how many external connections?
a) 3
b) 5
c) 2
d) 4
b
