8. NATE Industry Competency Exam:
Commercial Refrigeration
With the condensing pressure and compressor speed remaining constant, a
decrease
suction in
pressure will cause
a(n):
a. Decrease in compressor capacity and decrease in
current.
b. Increase in compressor capacity and decrease in
current.
c. Increase in compressor capacity and increase in
current.
d. Decrease in compressor capacity and increase in current. correct
answers D
An indication of non-condensable gas in a refrigeration system is
significantly:
a. Lower-than-normal suction
pressures.
b. higher-than-normal suction
pressures.
c. Lower-than-normal head
pressures.
d. higher-than-normal head pressures. correct
answers D
An automatic expansion valve controls refrigerant flow to an evaporator by
maintaining
a
constant:
a. Suction
pressure.
b. Pressure differential across the valve
port.
c. Liquid line
pressure.
d. Superheat. correct
answers A
What is the approximate compression ratio of a compressor operating at 35
psig suction
pressure and 135 psig discharge
pressure?
a.
1:03.
b.
3:01.
c.
1:04.
d. 4:01. correct
answers B
The BTUs rejected at the condenser are always greater than the heat
absorbed in the
evaporator
because:
a. The condenser is mounted outside with restricted
airflow.
b. Of the high temperature of the discharge vapor and length of the
discharge
c. line.
Of the inefficiency of the condenser and pressure drop in the
discharge
d. line.of compression in the compressor. correct
Of the heat
answers D
,A unit cooler is inspected and found to be completely iced up. The heaters
and defrost
timer are found to be working properly. A technician
should:
a. Adjust the defrost termination switch to a higher
temperature
b. Adjust the setting.
thermostatic expansion valve to a higher
superheat setting.
c. Clear all of the ice from the coil and find out why the coil
is frosted.
d. Increase the frequency of the defrost cycle. correct
answers A
what is the correct gauge pressure corresponding to an absolute pressure of
24.7
at seapsia
level?
a. 10
psig.
b. 12.6
psig.
c. 39.4
psig.
d. 39.7 psig. correct
answers A
For a lineup of medium temperature case, an evaporator temperature
0f 23°F isThe following conditions
needed.
exist:
· The suction line pressure drop is equivalent to
·approximately
The liquid line2°F.
pressure drop is equivalent
to 1°F.
The compressor capacity should be selected based on a saturated suction
temperature
of
:
a.
20°F.
b.
21°F.
c.
23°F.
d. 25°F. correct
answers B
What is true of systems with multiple evaporators at different
temperatures?
a. It is required to install evaporator pressure
regulator(s).
b. The compressor discharge pressure will be a function of the
coldest
c. space. to install a head pressure control
It is required
valve.
d. It is required to install a crankcase pressure regulator. correct
answers A
If charging a system by subcooling, what metering devices is
installed?
a. Capillary
tube.
b.
Restrictor.
c. Thermostatic expansion
valve.
d. Fixed orifice. correct
answers C
The most critical refrigerant line with respect to sizing for compressor
performance is
the
:
a. Liquid
line.
, b. Discharge
line.
c. Suction
line.
d. Bypass line. correct
answers C
In a liquid line, excess pressure drop can
cause:
a. Sweating suction
lines.
b. Flash
gas.
c. Compressor
overload.
d. Liquid subcooling. correct
answers B
What are the two factors making up the safety classification for
refrigerants?
a. Toxicity and time weighted
average.
b. Toxicity and
flammability.
c. Emergency exposure limit and time weighted
average.
d. Flammability and TEWI. correct
answers B
What would be most affected by the use of an oversized
suction line?
a. Discharge
temperature.
b. Oil
return.
c. Return gas
temperature.
d. Refrigerant migration. correct
answers B
On an electrical diagram, the below symbol represents a
control that:
a. Closes on pressure
rise.
b. Opens on pressure
rise.
c. Closes on temperature
d. Opens on temperature rise. correct
fall.
answers B
During the pulldown periods of single compressor condensing units,
compressor
overloading can best be prevented by
using a(n):
a. Thermostatic expansion
b. Evaporator pressure regulating
valve.
valve.
c. Crankcase pressure regulating
valve.
d. Head pressure valve. correct
answers C
The purpose of a crankcase heater
is to:
a. Reduce refrigerant migration into the oil during the
offMinimize
b. cycle. refrigerant flooding into the
compressor.
c. Remove any oil that may have migrated into the
refrigerant.
d. Warm the oil to allow compressors to start easier. correct
answers A
Commercial Refrigeration
With the condensing pressure and compressor speed remaining constant, a
decrease
suction in
pressure will cause
a(n):
a. Decrease in compressor capacity and decrease in
current.
b. Increase in compressor capacity and decrease in
current.
c. Increase in compressor capacity and increase in
current.
d. Decrease in compressor capacity and increase in current. correct
answers D
An indication of non-condensable gas in a refrigeration system is
significantly:
a. Lower-than-normal suction
pressures.
b. higher-than-normal suction
pressures.
c. Lower-than-normal head
pressures.
d. higher-than-normal head pressures. correct
answers D
An automatic expansion valve controls refrigerant flow to an evaporator by
maintaining
a
constant:
a. Suction
pressure.
b. Pressure differential across the valve
port.
c. Liquid line
pressure.
d. Superheat. correct
answers A
What is the approximate compression ratio of a compressor operating at 35
psig suction
pressure and 135 psig discharge
pressure?
a.
1:03.
b.
3:01.
c.
1:04.
d. 4:01. correct
answers B
The BTUs rejected at the condenser are always greater than the heat
absorbed in the
evaporator
because:
a. The condenser is mounted outside with restricted
airflow.
b. Of the high temperature of the discharge vapor and length of the
discharge
c. line.
Of the inefficiency of the condenser and pressure drop in the
discharge
d. line.of compression in the compressor. correct
Of the heat
answers D
,A unit cooler is inspected and found to be completely iced up. The heaters
and defrost
timer are found to be working properly. A technician
should:
a. Adjust the defrost termination switch to a higher
temperature
b. Adjust the setting.
thermostatic expansion valve to a higher
superheat setting.
c. Clear all of the ice from the coil and find out why the coil
is frosted.
d. Increase the frequency of the defrost cycle. correct
answers A
what is the correct gauge pressure corresponding to an absolute pressure of
24.7
at seapsia
level?
a. 10
psig.
b. 12.6
psig.
c. 39.4
psig.
d. 39.7 psig. correct
answers A
For a lineup of medium temperature case, an evaporator temperature
0f 23°F isThe following conditions
needed.
exist:
· The suction line pressure drop is equivalent to
·approximately
The liquid line2°F.
pressure drop is equivalent
to 1°F.
The compressor capacity should be selected based on a saturated suction
temperature
of
:
a.
20°F.
b.
21°F.
c.
23°F.
d. 25°F. correct
answers B
What is true of systems with multiple evaporators at different
temperatures?
a. It is required to install evaporator pressure
regulator(s).
b. The compressor discharge pressure will be a function of the
coldest
c. space. to install a head pressure control
It is required
valve.
d. It is required to install a crankcase pressure regulator. correct
answers A
If charging a system by subcooling, what metering devices is
installed?
a. Capillary
tube.
b.
Restrictor.
c. Thermostatic expansion
valve.
d. Fixed orifice. correct
answers C
The most critical refrigerant line with respect to sizing for compressor
performance is
the
:
a. Liquid
line.
, b. Discharge
line.
c. Suction
line.
d. Bypass line. correct
answers C
In a liquid line, excess pressure drop can
cause:
a. Sweating suction
lines.
b. Flash
gas.
c. Compressor
overload.
d. Liquid subcooling. correct
answers B
What are the two factors making up the safety classification for
refrigerants?
a. Toxicity and time weighted
average.
b. Toxicity and
flammability.
c. Emergency exposure limit and time weighted
average.
d. Flammability and TEWI. correct
answers B
What would be most affected by the use of an oversized
suction line?
a. Discharge
temperature.
b. Oil
return.
c. Return gas
temperature.
d. Refrigerant migration. correct
answers B
On an electrical diagram, the below symbol represents a
control that:
a. Closes on pressure
rise.
b. Opens on pressure
rise.
c. Closes on temperature
d. Opens on temperature rise. correct
fall.
answers B
During the pulldown periods of single compressor condensing units,
compressor
overloading can best be prevented by
using a(n):
a. Thermostatic expansion
b. Evaporator pressure regulating
valve.
valve.
c. Crankcase pressure regulating
valve.
d. Head pressure valve. correct
answers C
The purpose of a crankcase heater
is to:
a. Reduce refrigerant migration into the oil during the
offMinimize
b. cycle. refrigerant flooding into the
compressor.
c. Remove any oil that may have migrated into the
refrigerant.
d. Warm the oil to allow compressors to start easier. correct
answers A
