WorksheetsType 3 (REVISED)
Total questions: 47
Worksheet time: 24mins
A typical setting for the high-pressure cut-out control on a recovery unit used for evacuating refrigerant from a low-pressure chiller is
2 psig
5 psig
10 psig
15 psig
A charged low pressure refrigeration system can be efficiently leak-checked by
adding compressed air since it will be removed from the system by the purging unit.
operating the purge system.
adding HCFC-22.
raising system pressure by heating with circulated hot water or heating blankets.
The existence of air in a low pressure system causes
low head pressure.
low suction pressure.
high head pressure.
high liquid level.
Which safety precaution should be adhered to for low pressure systems?
Do not siphon refrigerant by mouth .. dummy.
Avoid spilling liquid refrigerant on your skin.
Use gloves and safety goggles when working with liquid refrigerant.
All of the above.
Refrigerant-11 (R-11) at 14.7 psia, will boil at about
60.3 F
74.5 F
79.7 F
When there is excessive moisture collecting in the purge unit of a low pressure refrigeration system, this indicates that
the system with contaminated refrigerant.
the condenser or chiller barrel tubes are leaking.
the purge unit is not operating properly.
the purge unit needs adjustment.
ASHRAE Standard 15-1994 requires equipment room refrigerant sensors for what safety group classification?
A1
B2
A2
All refrigerant safety groups.
When recharging a refrigeration system with R-11, what vapor pressure is necessary in the shells before charging with liquid?
21.1 inch Hg vacuum
19.7 inch Hg vacuum
18.1 inch Hg vacuum
16.9 inch Hg vacuum
After reaching the required recovery vacuum on a chiller, you should
Immediately disconnect the recycling or recovery equipment and open the system for service.
wait for at least a few minutes to see if the system pressure rises, indicating there is still refrigerant in liquid form or in the oil.
Immediately break the vacuum with nitrogen and open the system for service.
Immediately pressurize the system with nitrogen and perform a leak check.
A hydrostatic tube test kit is used to
blow all water from the tubes.
remove any water from the machine.
vent refrigerant.
determine if a tube leaks.
When charging a chiller, refrigerant vapor is introduced into the system before charging with liquid refrigerant. This is because
charging with vapor increases pressure slowly, preventing failure of the rupture disk.
charging with vapor is faster than charging with liquid.
liquid charging is more difficult to control than vapor charging.
liquid charged into a deep vacuum will cause the refrigerant to boil and may lower temperatures enough to freeze the water in the tubes.
When evacuating a system, the use of too large a vacuum pump can cause
trapped water to freeze.
trapped oil to freeze.
trapped refrigerant to freeze.
valves to freeze.
On a low pressure chiller with an open-type compressor, the ________ is/are very susceptible to leaks.
chiller tubes
shaft seal
charging connections
shaft bearings
What steps may be taken to prevent air accumulation into an idle low-pressure refrigeration system?
Leave the purge unit on at all times.
System pressure should be maintained slightly above atmospheric pressure.
Open the air vents on the condenser.
Intermittently operate the system with no load.
When recovering vapor from a low pressure refrigeration system,
the water pumps should be on, and the recovery compressor should be off.
the system water pumps should be on, the recovery compressor should be on, and the recovery condenser water should be off.
the system water pumps, the recovery compressor, and the recovery condenser water should all be on.
the system water pumps should be off, and the recovery compressor should be on.
After leaving the purge unit of a low pressure centrifugal system, the refrigerant goes to:
the evaporator
the condenser
the compressor
the expansion valve
Which of the following is the component from which the purge unit takes its suction?
The evaporator
The condenser
The compressor intercooler
The recovery service vessel
The purge unit takes its suction from the
top of the condenser.
compressor oil sump.
top of the evaporator.
suction elbow.
Which of the following repairs would ALWAYS be considered a “major” repair under EPA’s regulations?
Replacement of an evaporator coil.
Replacement of a filter-drier.
Replacement of a switch.
Replacement of a purge unit.
Charging liquid refrigerant into a refrigeration system when it is under a 29-inch Hg vacuum can cause the
liquid refrigerant to absorb excess moisture.
purge unit to operate.
system water to freeze.
liquid refrigerant to freeze.
According to the EPA there is approximately ______ of refrigerant vapor left in an average 350 ton R-11 chiller at 0 psig pressure once all the R-11 liquid has been removed.
0 lbs
10 lbs
20 lbs
100 lbs
An oil sample should be taken when
a new filter drier has been installed.
there has been a compressor burnout.
the unit is not cooling properly.
recycled refrigerant has been added to the unit.
Both CFC-11 and HCFC-123 chillers require purge units because
the purge units remove moisture.
the system operates below atmospheric pressure.
purge units remove refrigerant from the oil sump.
purge units remove CFCs from the chiller.
Under EPA regulations, ________ is used to pressurize a low-pressure chiller for the purpose of opening the system for a non-major repair.
adding nitrogen
warming the refrigerant
adding compressed air
adding carbon dioxide
The primary water source for a recovery unit condensing coil is
chilled water.
condenser water.
the local municipal water supply.
de-ionized water.
Which statement is NOT true of recycling and recovery equipment manufactured after November 15 1993?
It must be tested by an EPA-approved third party.
It must meet vacuum standards more stringent than those met by equipment manufactured before November 1 1993.
It must be equipped with low-loss fittings.
It must be able to handle more than one refrigerant.
A system does not have to be evacuated all the way to the required level when
the repair is major.
the repair is followed by an evacuation of the appliance to the environment.
the appliance is being disposed.
leaks in the appliance make evacuation to the prescribed level impossible.
Which action listed below is the proper method to reduce refrigerant loss from a purge unit on a CFC-11 chiller?
Leak-test and repair the chiller.
Seal the purge-unit discharge.
Pipe purge-unit back into the low side.
Pipe purge unit into recovery unit.
Identify the pressure corresponding to 32F for R-123:
32F for R-123
18.2 psia
22.3 psia
25.6 psia
What precaution should be taken prior to recovering refrigerant from a chiller suspected of having tube leaks?
Drain the water sides of the evaporator and condenser.
Run the circulating pumps.
Be certain the purge unit is operating.
Open the condenser vents.
Pressure relief valves must never be
installed in series.
installed in parallel.
installed vertically.
installed horizontally.
If you are going to be removing oil from a low-pressure system, you should heat the oil because
you can warm your hands on the container.
less refrigerant will be contained in the oil at high temperatures.
warmer oil has a lower viscosity and flows more easily.
it shows that the heater is working.
After recovering the liquid refrigerant you must
recover the refrigerant vapor.
pressurize the system with nitrogen.
remove the oil from the system.
solvent-flush the entire system.
EPA regulations require that any appliances containing more than 50 pounds of refrigerant, except for commercial and industrial, must be repaired when the leak rate exceeds:
15% in a 12-month period
10% in a 12-month period
20% in a 12-month period
25% in a 12-month period
Process refrigeration must be repaired when the leak-rate exceeds _____ of the charge per year.
5 percent
10 percent
20 percent
35 percent
If you are using a recovery machine manufactured BEFORE November 15 1993, you must evacuate any low-pressure appliance to _____ before making a major repair.
0 psig
15 inches of Hg vacuum
25 inches of Hg vacuum
25 mm of Hg absolute
On low-pressure chillers, moisture typically enters the refrigerant system through
air leaks in the rupture disk assembly.
tube leaks.
air leaks from areas with gaskets or fittings.
air leaks from the charging valve.
Refrigerant-11 at a pressure of 17 inches Hg vacuum has a saturation temperature of
30 F
35 F
40 F
44 F
The lowest access point on a low-pressure centrifugal air-conditioning unit is the
evaporator charging valve.
condenser service valve.
compressor cooler jacket.
purge unit exhaust port.
A rupture disc on a recovery vessel for low-pressure refrigerants relieves at
5 psig
10 psig
15 psig
20 psig
During chiller evacuation, water is circulated to
speed up the recovery process.
prevent loss of refrigerant to the atmosphere.
prevent freezing of the water.
maintain constant refrigerant pressure.
ASHRAE Standard 15-1994 requires that each machinery room must activate an alarm and mechanical ventilation before refrigerant concentrations exceed
the EEL (Emergency Exposure Limit)
the TLV - TWA (Threshold Limit Value - Time Weighted Average)
the UTL (Upper Threshold Limit)
the COP (Coefficient of Performance)
Which repair WOULD NOT fall under the EPA definition for major maintenance, service, or repair?
Replacing an oil filter.
Replacing the compressor.
Re-tubing a condenser.
Replacing a fin and tube forced air evaporator coil.
Refrigerant is added to a centrifugal machine through the
float valve.
compressor service valve.
condenser charging valve.
evaporator charging valve.
What is meant by the term “high efficiency purge unit”?
Those purge units which discharge a high percentage of refrigerant with the air they remove.
Those purge units which discharge a low percentage of refrigerant with the air they remove.
Those purge units which draw very little electrical power.
None of the above.
The primary purpose of a purge unit on a CFC-11 chiller is to
remove CFCs from the system.
condense air out of the system.
condense water out of the system.
remove noncondensables from the system.
If you are using a recovery machine manufactured AFTER November 15 1993, you must evacuate any low pressure appliance to _____ before making a major repair.
0 psig
15 inches of Hg vacuum
25 inches of Hg vacuum
25mm of Hg absolute
