Re-Fresher #2 Flashcards
An emergency shut off valve may be installed between a pressure vessel and the emergency discharge valve only under certain conditions. T or F?
F
Feeder protection for freon hermetic compressor must never exceed 225% of FLA according to the Canadian electrical code. T or F?
F
Oil failure control protects compressor against loss of oil lubrication by sensing two pressures: crankP and pumpP to achieve netPoilP. This works on principle of heat and bi-metal action. T or F?
T
backward inclined fan is all known as a no load or non overloading fan. True or False?
T
A dual element fuse is used to protect a compressor motor from excessive starting current only. True or False?
F
Voltages that can be obtained from a delta closed distribution transformer are 208/1/60, 208/3/60, 240/3/60, 120/1/60. T or F?
F
The reversing valve as used with a heat pump system should be replaced after a system burnout of 0.5or greater has occurred. T or F?
T
Normal compression ratio for a centrifugal compressor is 5:1. T or F?
F
For accurate readings of liquid line moisture indicators its temp should be 70degF. T or F?
F
Refrigerant 12 driers should be at least 3-5 times as large as driers used for refrigerant 22 or 500. True or False?
F
A CRO is used to control condenser pressure during periods of low ambient temperatures (below 70f) on air cooled condensers. T or F?
F
With direct staging compression systems cooling of freon vapour between the discharge of 1st and inlet of second comp is needed.
T or F?
F
Calcium chloride may be stored in the same equipment room as ammonia as long as it is safe to do so. T or F?
F
Copper and brass is always used with ammonia gas because of their non-corrosive action in the presence of moisture. T or F?
F
Calculation for COP is Btu’s output/kw input x 3425. T or F?
F
A direct acting controller means that, an increase in output energy, as it senses an increase in controlled variable. T or F?
T
Temp sensors of the electrical resistance type will always have a positive temperature coefficient. T or F?
F
Protection for branch circuit feeding a refrigeration hermetic compressor should be sized at _____ of RLA
a) 110%
b) 125%
c) 140%
d) 225%
B
A perfect vacuum can be expressed by what pressure?
a) 0psig
b) 0psia
c) 29.4” hg vac
d) 10 microns
B
The capacity of an evaporative condenser/cooling tower is
a) greater when wet bulb temp is low
b) greater when wet bulb temp is hi
c) lower when wet bulb is low
d) greater when humidity is higher
A
A liquid receiver must be capable of storing what percentage of a system charge?
a) 125%
b) 120%
c) 110%
d) 90%
D
Efficiency of a compressor could be stated as
a) how cold suction line is compared to discharge
b) how hot condenser is
c) diff between high and low gauge
d) none of the above
D
What is the safety device located and installed on a gauge glass level indicator in case of breakage?
a) hand valve
b) solenoid valves
c) ball check pins
d) ball check valves
D
A sample evap coil operates at a design TD of 8F. What will the relative humidity in the condition space?
a) 80-90%
b) 70-80%
c) over 90%
d) 90%
C