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)