ASSIGNMENT 4
Textbook Assignment:
"Refrigeration and Air Conditioning," "Compressed Air Systems,"
"Laundry, Mess Decks, Galley, and Scullery Equipment," "Other
Auxiliary Equipment," and "Lathe and Machining Operations," chapters
5 through 9, pages 5-9 through 9-20.
4-1.
Which of the following conditions
may be caused by excessive buildup
of frost on the cooling coils?
1. Low suction pressure
2. High suction pressure
3. Low suction temperature
4. High condensing pressure
4-2.
The maximum time between defrosting
of the cooling coils depends on
which of the following factors?
1.
Amount of refrigerant in the
system
2.
Moisture content of the
supplies placed in the box
3. Amount of heat to be removed
4.
All of the above
4-3.
You must defrost the cooling coils
before the frost reaches what
maximum thickness?
1.
1/8 inch
2.
3/16 inch
3.
1/4 inch
4.
5/16 inch
IN ANSWERING QUESTION 4-4, REFER TO FIGURE
5-4 OF THE TEXTBOOK.
4-4.
Approximately how many inches of
mercury represent the difference in
temperature between points B and D?
1.
0.200 inch absolute
2.
0.232 inch absolute
3.
0.436 inch absolute
4.
0.640 inch absolute
4-5.
While you are evacuating and
dehydrating a refrigeration system,
the vacuum indicator fails to
attain 35°F.
Which of the
following conditions may be the
cause of this failure?
1.
Lack of lubricating oil in the
compressor crankcase
2.
Lack of moisture in the system
3.
Presence of R-12 in the
lubricating oil
4.
Each of the above
4-6.
To be properly reactivated,
dehydrating agents should be heated
(a) at what specific temperature
and (b) for what approximate length
of time?
1.
(a) 200°F; (b) 12 hr
2.
(a) 300°F; (b) 12 hr
3.
(a) 400°F; (b) 6 hr
4. (a) 500°F; (b) 6 hr
4-7.
If you do not have a tank-type
cleaner, you can clean an R-12
system by which of the following
methods?
1.
By flushing boiling water
through the system three times
2.
By blowing hot air through the
system for 24 hours
3. By inserting a hard, wool felt
filter in the suction strainer
screen and operating the plant
4.
Each of the above methods
4-8.
On the two-position, dual control
(2PD), which of the following
system types uses one common
cooling coil to service several
different spaces?
1. 1
2. 2
3. 3
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