Exam (elaborations)
HVAC FINAL EXAM QUESTIONS AND ANSWERS 2024
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HVAC FINAL EXAM QUESTIONS AND ANSWERS 2024
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HVAC FINAL EXAMA system using R-404a has an evaporation temperature of 0°F. If the line length is
100 ft. and the system needs a capacity of 2 tons, what size line should be used? -
ANSWERS-7/8 in
Refrigerant oil flow through the liquid line is not a problem because: - ANSWERS-
The oil mixes with the liquid refrigerant.
Flash gas in the liquid line can be identified by: - ANSWERS-A significant
temperature drop in the liquid line temperature.
In a parallel compressor system, oil often does not return at the same rate to all
of the compressors because: - ANSWERS-All the compressors do not operate for
the same length of time.
Which pair of factors most directly affects the maximum allowable pressure drop
within a system? - ANSWERS-Temperature of refrigerant and type of refrigerant
For most systems, the minimum velocity in a horizontal suction line is: -
ANSWERS-750 - 1000 feet per minute.
For most systems, the minimum velocity in a vertical suction line is: - ANSWERS-
1000 - 1500 feet per minute.
,The refrigerant line whose sizing has the most effect on the compressor's
compression ratio is the: - ANSWERS-Suction line
What is an oil lift? - ANSWERS-An oil lift is a trap at the bottom of a vertical
suction riser.
Why are vertical suction risers often smaller than the horizontal runs on the same
suction line?` - ANSWERS-The risers are sized smaller to maintain a minimum
velocity to lift the oil.
One difference between refrigerant piping practices for air conditioning systems
and refrigerant piping practices for commercial refrigeration systems is that: -
ANSWERS-Most air conditioning manufacturers do not recommend oil traps
Why is it necessary to purge gauge manifold valves while they are connected? -
ANSWERS-To prevent contamination of the system
Why do some technicians recommend using a separate refrigerant tank when
purging hoses? - ANSWERS-To preserve the system charge.
When a manual service valve is front seated: - ANSWERS-The service port is open
and the system is closed to the line.
,What controls when Shrader valves open and close? - ANSWERS-They open and
close when hoses with depressors are connected and disconnected to them.`
One way to reduce the amount of refrigerant spray when connecting and
disconnecting refrigeration hoses from Schrader valves is to: - ANSWERS-Use
positive shut off hoses.
What types of system access valves do residential air conditioning systems usually
have? - ANSWERS-Shrader valves on the suction line and liquid line
When connecting gauges to an already installed and operating unit with split
system installation valves, the installation valves should be - ANSWERS-Left alone.
If a technician needs to read the refrigerant pressure of a window unit, they must:
- ANSWERS-Use a piercing valve.
After servicing a system using bolt-on piercing valves, the technician should: -
ANSWERS-Recover the refrigerant, remove the bolt-on valve and replace it with a
permanent valve.
Commercial refrigeration systems normally have: - ANSWERS-A suction service
valve, discharge service valve, and a king valve.
Which is the primary purpose of a split-system installation valve's service port?
, A) System evacuation
B) Valve maintenance
C) Controlling leaks
D) Trapping refrigerant - ANSWERS-A)
System evacuation
What is the problem associated with disconnecting a gauge manifold through its
middle leg? - ANSWERS-There is a loss of refrigerant.
Which refrigeration hose end has a Schrader valve core depressor? - ANSWERS-
The crooked end
How do the three position service valves differ from other valves? - ANSWERS-
They have no closed position.
What type of units are required by the EPA to have service valves? - ANSWERS-
Type II and Type III
Why are split-system installation valves typically not used following installation? -
ANSWERS-They do not control flow to service ports.
What types of system access valves do household refrigerators usually have? -
ANSWERS-A process stub on the compressor
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