Practice Test Flashcards
Horsepower will increase as ____ and decrease as ____
Increases as the head pressure increases and dcreases as suction pressure increases
A solenoid valve ____
does not vary the flow of refrigerant into the evaporator
The TEV ____
Modulates and controls the flow of refrigerant into the evaporator
If you use an automatic exspansion valve with a variable load you will ____
Starve the evaporaot
An automatic expansion valve with a variable load will ____
Starve the evaporator
An automatic expansion valve maintains ____
constant evaporator pressure
If the evaporator doesn’t respond to the adjustments of the TEV it may be due ____
To oil logged on the low side
Noncondensibles can cause ____
High head pressure
The purpose of having a compressors in a cascade system is to operate at ____
Very low temperatures
A pressure relief valve is better than a fusible plug because ____
A fusible plug cannot be reset
If the TEV’s spring was to break it would ____
Flood the evaporator and raise suction pressures
The TEV equalizer Line makes up for the ____
Pressure drop in the evaporator
Semi Hermetic compressors have the advantage over hermetic because
They can be serviced on site
When using a portable compressor recovery unit to remove vapor the ____
Vapor density is decreased
Unloaders are used to ____
Decrease capacity
The amount of pressure that flows through the orifice plates is determined by the ____
Difference in pressure between the high and low sides
A TEV restricts the amount of refrigerant from the ____
High to low side
A halide torch turns from ____ when a leak is detected
Blue to green or purple
A rectifier turns ____
AC voltage to DC voltage
A thermostat will ____
Cycle compressors
The main reason for a crankcase breather line is to prevent ____
Oil from slugging in the compressor
The middle port on a manifold gauge will be connected to the ____
Recovery cylinder or the charging cylinder
A forced draft cooling tower is better than a natural draft because it is ____
Smaller and not affected by prevailing winds
Solenoids and motors work on ____
Watts
R-22 at 38 degrees is ____
65.6 psi
A purge unit disposes of ____
Non condensibles
An overcharge of refrigerant can cause ____
High head pressure
A sling psychrometer if both wet and dry bulb temps were the same would indicate ____
A lot of relative humidity
A vertical shell and tube condenser uses a ____ to force down the tubes proving good heat transfer
Swirler at the top of the water box
The muffler is located ____
Between the compressor and the condenser
A brine solution with a ph of 7.8 is ____
Slightly alkaline
If the TEV sensing bulb is clamped at the center of the evaporator it cause ____
excessive superheat
Subcooling indicates the performance of the ____
Condenser
A stuffing box lantern is made of ____
Metal with oil circulating through it
TEV’s are rates in ____
Tons of refrigeration
An anemometer measures ____
Air velocity
You check motor windings with an ____
Ohmmeter
A filter drier removes ____
Moisture, acids, and contaminants
When removing a service valve stem cap remove ____
Slowly
Charging liquid using a gauge manifold the ____
High side is open and the low side is closed
In a 3 stage centrifugal chiller the ____
Pressure increases as it reaches its final stage
Inducing draft cooling tower the lowest temp attainable for cooling tower water is ____
Higher than the wet bulb
A compressor safety head is a ____
Pressure relief device
A centrifugal machine is characterized by ____
High volume and low pressure
If condenser pressure is high and another pump has to be turned in you would have the ____
Suction valve be completely opened and the discharge valve opened to a throttling position
If you disconnected the external equalizer on a TEV you would ____
Starve the evaporator
You achieve capacity control on a reciprocating compressor by ____
Opening suction valves by using some form of control
A sling psychrometer is used to measure ____
Relative humidity
The ratio of actual water vapor in the atmosphere to the saturation pressure is called ____
Relative humidity
Refrigerant effect is always lower than latent heat because ____
Heat required to cool the refrigerant from compressor discharge to evaporator temperature is subtracted from latent heat
You use a TEV with an external equalizer when there is more than a ____
2.5 pressure drop through the evaporator coil
Cylinder Unloaders are used for
Controlling capacity
R-22 head pressure with condenser water temperature if 85 degrees is ____
200-215 psi
When you run 2 pumps in parallel you ____. Pressure is the same when running 1 or 2 pumps
Increase total flow rate (gpm)
Frost in the suction line and compressor could be caused by the ____
TEV being opened to wide
If cooling tower is not chemically treated it could cause ____
Bacteria growth and rusty pipes
The low-pressure control _____ off and on
Cycles the compressor
____ require an oxygen deprivation sensor (R-12, R-12, R-22, R-134A)
All group 1 refrigerants
A low pressure chiller’s rupture disc is set at ____
15 psi
An automatic purge unit is required for systems that operate ____
Below atmospheric pressure (in a vacuum)
An undesirable property in a refrigerant is ____
Low latent heat
Scale particles lodged in a TEV could cause ____
High super heat
High head pressure and temperature could be caused by ____
Dirty condenser tubes
If wet bulb temperature decreases it can ____
Lower the temperature of the cooling tower water
You can always charge refrigerant into the ____
Low side
Clogged eliminator fins on a cooling tower could lead to a ____
Higher temperature supply
A jet ejector if restricted will have ____
Insufficient head to lift the oil back to the oil sump
The low side gauge (saturation pressure) can be used to ____
Estimate chill water temperature
Water tube leaks a low-pressure chiller cab be found with a ____
Hydrostatic tube test
R-11 and R-123 refrigerants are ____
Oxygen depleting, heavier than air, and class 1 and class 11 substances
A centrifugal chiller purge unit first ______________
Takes a combination of air and refrigerant from the top of the condenser, then removed air and non condensibles, and finally returns liquid refrigerant back to the condenser
_______ are use to defrost evaporators
Electric resistance heaters (resistor circuit)
Low condensing pressure is not good because ____
Expansion valves will not feed properly
An in-line refrigerant cleaning system is advisable because ____
Refrigerant reacts with lube oil
If the water pump is facilitating this problem could be caused by ____
A faulty water level control
Capacitors are devices which have the ability to ____
Store electricity and used to start motors
The refrigerant with the highest latent heat is ____
Ammonia
____ are electric devices which change the value of AC voltage to another AC voltage
Transformers
The maximum pressure to leak test low pressure chillers is ____
10 psig
Under EPA regulations you can pressurize a system for a ____
Non major reissue with nitrogen
Under EPA regulations replacement of an evaporator coil is ____
Always considered a major repair
R-11 at 14.7 psia (0 psig) will boil at approximately ____
74.5 degrees
If a system is excessively cycling ,crankcase temp is high, discharge is low and suction is high this could be caused by ____
Faulty compressor valves
Centrifugal compressors can control capacity with ____ and/or ____
Variable guide vanes and/or variable speed motors
On a reciprocating compressor there are stop valves on the ____
Inlet (suction side) and the outlet (discharge side)
Refrigerant is added to a low-pressure centrifugal chiller through the ____
Evaporator charging valve
You can store ___% refrigerant on site
20%
Before a low-pressure appliance is dismantled and salvaged ____
Refrigerant must be recovered
Chill water pumped are ____
Always insulated
Compound gauges measure ____
positive and negative pressure
Oil pressure should be at least ____ in a reciprocating compressor
15 to 30 pounds above the suction pressure
The motor is connected to the pump with a ____
Flexible coupling
She’ll and COIL condensers are not mechanically serviceable and must be cleaned ____
Chemically
Shell and TUBE condensers can be _____
Mechanically cleaned with brushes
Water regulating valves work off of ____
Head pressure
Outdoor cooling towers have ____ to prevent freezing
Heater coils
A refrigeration system with a cooling tower the heat from the building sis rejected as the ____ in the cooling tower
Heat of evaporation
An older type of cylinder Unloaders is designed to control ____
Cylinder clearance pockets
An efficient condenser runs with a ____
Low condenser pressure
If a unit using a low side float was short cycling it could need ___
Additional refrigerant to be charged
A disadvantage if fusible plug is that it ____
Only works on temperature
If a centrifugal pump is running fine at full discharge but if throttled it loses flow a ____ could be the cause
Clogged strainer
A compressor stuffing box prevents the ____
Leaking of refrigerant vapor
The AEV works on 2 pressures ____
Evaporator pressure is opening pressure and spring pressure is closing pressure
The most superheat occurs after when ____
Boiling is complete
High pressure is found ____ and low pressure is ____
Above the valve plate and below the valve plate
Automatic water regulating valves vary water flow according to ____
Condenser Head Pressure
