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- 1. Multiple Choice
The high and low pressures in a refrigeration system are separated by the:
Condenser and metering device
Evaporator and compressor
Metering devise and compressor
Filter drier and liquid line
- 2. Multiple Choice
The pressure at which the refrigerant changes state, from a vapor to a liquid is the:
Evaporation pressure
Superheated perssure
Back pressure
Condensing pressure
- 3. Multiple Choice
A pressure gauge placed anywhere, from the metering device to the compressor will read:
The low side or evaporating pressure
The head pressure
The total high pressure
The sub cooling
- 4. Multiple Choice
Most modern refrigerants exist either in:
(a) The saturated vapor state
(b) The saturated liquid state
Answers (a) and (b) are true
Solid state
- 5. Multiple Choice
In an operating system, you should have liquid and vapor in the:
Evaporator only
Condenser only
Compressor
Evaporator and condenser
- 6. Multiple Choice
The term, Refrigerant "Conditions" refer to which of the following?
Saturated, superheated or subcooled refrigerant
Pressurized refrigerant only
A system in a complete vacuum
The outdoor ambient temperature
- 7. Multiple Choice
The heat energy that causes a liquid refrigerant to change to a vapor at a constant saturation temperature for a given pressure is referred to as:
Sensible heat
Latent heat
Superheat
Subcooled
- 8. Multiple Choice
The temperature/pressure chart is only good when the refrigerant is in the:
Saturated liquid state only
Saturated vapor state only
Superheated saturated state only
Liquid and vapor mixed
- 9. Multiple Choice
Superheat always refers to:
(a) A liquid refrigerant
A vapor
(c) A mixture of liquid and vapor
Both (a) and (c)
- 10. Multiple Choice
Subcooling always refers to:
A vapor cooled elow its saturation temperature
A liquid cooled below its saturation temperature
The refrigerant that cools the compressor
The flashing of refrigerant at the metering device
- 11. Multiple Choice
The basic components of a refrigeration unit are:
Compressor, discharge line, condenser, metering device, receiver, evaporator and suction line.
Filter drier, receiver, high and low sides
Condenser, discharge line, condenser, metering device, receiver, and suction line
Compressor, metering device and referigerant
- 12. Multiple Choice
In the first few passes of the condenser:
The refrigerant should be de-superheated
The refrigerant should completely change to a vapor
The refrigerant should completely change to a liquid
The pressure should drastically drop
- 13. Multiple Choice
One of the main functions of a condenser is to:
(a) Change the liquid to a vapor
(b) Superheat the liquid
Change the refrigerant vapor to a liquid
Both (a) and (b)
- 14. Multiple Choice
Subcooling can be defined as:
The cooling effect of the refrigerant in an evaporator
Any sensible heat taken away from 100% saturated liquid
The superheat taht is removed at the top of the condenser
The cooling of the compressor motor by returning refrigerants
- 15. Multiple Choice
The component in the refrigeration system used to catch and prevent liquid from entering the compressor is called the:
The liquid receiver
The accumulator
The oil separator
The filter drier
- 16. Multiple Choice
The greatest advantage of a TXV over a capillary tube or fixed metering device is the:
Cost factor
Capillary tube can adapt to the load very quickly
TXV can adapt to the load very quickly
TXV can completely stop the refrigerant flow
- 17. Multiple Choice
The greatest need for "subcooling" the refrigerant is to:
Prevent liquid line flash, thus making the system much more efficient
Cool the refrigerant suction line
Prevent liquid from entering the compressor
To store liquid in the filter drier
- 18. Multiple Choice
The purpose for a LLiquid Pressure Amplification LPA is to:
Increase the superheat only.
Increase the liquid pressure only.
Help prevent flashing and increase sub cooling.
Increase the liquid pressure and sub-cooling.
- 19. Multiple Choice
The refrigerant charge in a TXV remote bulb or power element must be:
Changed when the filter drier is changed
Identical to the refrigerant in the system.
Discharged before it is effective.
R-134a
- 20. Multiple Choice
The External equalizing tube on the TXV is used on:
Units with a high efficiency condenser
Units with a pressure drop due to condenser length.
All refrigeration applications.
Long evaporators having a significant pressure drop.
- 21. Multiple Choice
The factory superheat settings for TXVs used with central air conditioning systems should be:
20 degrees or more
Less than 5 degrees
About 10 degrees
Reset by the installer
- 22. Multiple Choice
The remote bulb of a TXV should be fastened to the:
Outlet of the TXV, about 6 inches
Inlet of the TXV, about 6 inches
Outlet of the condenser and on the superheat line.
Outlet of the evaporator.
- 23. Multiple Choice
The refrigerant passing through a filter drier on the high side of the system should be in what state?
Superheated vapor
Gaseous
Saturated vapor
Liquid
- 24. Multiple Choice
The TXV's operation uses which of the following pressures?
Remote bulb, spring pressure and superheat
Remote bulb, spring pressure and evaporator pressure
Discharge, suction and spring pressures
External pressures only
- 25. Multiple Choice
At higher loads, a sight glass located in the liquid line of a refrigeration system will:
Bubble if the system is undercharged.
Have no bubbles.
Be perfectly clear.
Turn yellow or green inside.
- 26. Multiple Choice
Always charge a TXV/receiver/sight glass system under a:
No load condition
Low load condition
High load condition
Warm weather condition
- 27. Multiple Choice
The initial refrigerant charge into an evacuated system should be made:
Into the running compressor as a liquid
Into the evaporator as a liquid with the compressor off.
A small amount of vapor first, followed by liquid into the high side.
Into the accumulator as a liquid first, followed by vapor.
- 28. Multiple Choice
The compressor superheat should always be:
Between 20 and 30 degrees
Less than 5 degrees
Prevented
Never be a concern
- 29. Multiple Choice
The evaporator temperature on an air conditioning system should be:
40-50 degrees F
No more than 32 degrees F
More than 50 degrees at all times.
20-30 degrees F
- 30. Multiple Choice
The refrigerant charge on a capillary tube system is:
Not critical on most unites
Very critical on all units
Critical on some units
Not critical on larger systems
- 31. Multiple Choice
The most accurate method of charging a capillary tube system is to:
Weigh the charge into an empty system
Check the sub cooling system first
Charge liquid directly into the compressor
Use the capillary tube subcooling method
- 32. Multiple Choice
An overcharge of refrigerant will result in:
Lower ampere draw for the compressor
Increased overall efficiency
Elevated head and suction pressures
Little or no effect on performance
- 33. Multiple Choice
The second best way to charge a capillary tube system is to:
Use the superheat charging table or curve
Listen to the sounds the compressor makes
Charge unit and watch for sweating or frost on the suction line
Add refrigerant until the evaporator gets cold.
- 34. Multiple Choice
An air conditioning system or heat pump must have:
550-600 cubic feet of air per minute across the evaporator coil.
500-550 cubic feet of air per minute across the evaporator coil.
400-450 cubic feet of air per minute across the evaporator coil.
Always less than 400 cubic feet of air per minute across the evaporator coil.
- 35. Multiple Choice
When using a charging chart on most fixed orifice type central air condition systems, the following temperatures and conditions must be known:
Outdoor dry bulb and superheat
Indoor wet bulb and superheat
Indoor wet and dry bulb, outdoor dry bulb, and a superheat
Indoor wet bulb and dry bulb temperatures only.
- 36. Multiple Choice
When charging air conditioning systems with a capillary tube or fixed orifice metering device, the technician should:
Consult with the manufacturer and use their exact method of charging and specifications.
Charge until the unit stops frosting back and add a few ounces
Charge the amount shown on the I.D. tag and add 6 ounces for losses.
Turn off most of the registers to slow down the airflow across the evaporator.
- 37. Multiple Choice
An automatic expansion valve is best suited;
when the system load remains fairly constant
whent he system load varies greatly
when the compressor must start often
when multiple evaporators are used.
- 38. Multiple Choice
A rise in evaporator pressure causes the automatic expansion valve to begin to;
open
close
flood the evaporator
starve the evaporator
- 39. Multiple Choice
In the evaporator;
heat is transferred from the refrigerated space to the refrigerant
latent heat is transferred from the refrigerant to the refrigerated space
the refrigerant changes from a vapor to a liquid
the refrigeration system reaches its highest pressure
- 40. Multiple Choice
A palance port TXV
has a needle valve that cancels out the effects of the liquid pressure
will automatically cancel out the pressure drop across the evaporator
has a vapor charged sensing bulb which connects to the liquid line
has a pressure sensing port which connects to the liquid line
- 41. Multiple Choice
A temperature differential across a filter-drier indicates;
a normal operation
a restricted filter-drier
a refrigerant overcharge
a refrigerant undercharge
- 42. Multiple Choice
A liquid receiver is used to;
prevent liquid refrigerant from reaching the compressor
separate oil from the liquid refrigerant
store liquid refrigerant
receive and store vapor refrigerant
- 43. Multiple Choice
An accumulator is used to;
prevent liquid referigerant from reaching the compressor
separate oil from the liquid refrigerant
store liquid refrigerant
receive and store vapor refrigerant
- 44. Multiple Choice
A sight glass would normally be located;
in the liquid line, before the metering device
in the liquid line, after the metering device
in the suction line, before the compressor
in the suction line, after the compressor
- 45. Multiple Choice
A partially clogged capillary tube can cause;
low head pressure
a starved condenser
a starved evaporator
a flooded evaporator
- 46. Multiple Choice
Which of the following is TRUE of a solenoid valve in a pump down system?
It is located after the metering device
It is located before the metering device
It is located after the vaporator
It is used instead of a metering device
- 47. Multiple Choice
A TEV sensing bulb which becomes detached from the suction line will cause these symptoms;
high suction pressure and lower than normal discharge pressure
high suction pressure and higher than normal discharge pressure
low suction pressure and lower than normal discharge pressure
low suction pressure and higher than normal discharge pressure
- 48. Multiple Choice
A liquid-to-suction heat exchanger is often used to;
decrease vapor superheat
increase liquid sub-cooling
decrease head pressure
increase flash gas in the suction line
- 49. Multiple Choice
Superheat suppression is the process of;
injecting liquid refrigerant into the compressor
injecting liquid refrigerant into the evaporator
injecting liquid refrigerant into the suction line
injecting liquid refrigerant into the discharge line
- 50. Multiple Choice
____ can be used for leak detection with ALL high pressure refrigerants
soap bubbles
halide torch
open flame
electronic halogen detector
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