Q & A Flashcards
(292 cards)
0
Q
What color are the gauges on a manifold gauge set?
A
Low pressure is blue, and High pressure is red.
1
Q
What are the typical uses of the center port gauge set?
A
Used during evacuation, charging, and recovery procedures.
2
Q
What are the typical ranges of the pressure measurements used on the gauges of a manifold gauge set?
A
High side is 0 to 500 PSIG;
Low side is 0 to 350 PSIG, and 0 to 30 in. Hg below atmospheric pressure.
3
Q
Is the refrigerant leaving a condenser at a high or low pressure? Is it a liquid or a gas?
A
High pressure, liquid.
4
Q
Is the refrigerant entering the expansion valve (variable metering device) a liquid or gas?
A
Liquid, high pressure.
5
Q
Is the pressure of the refrigerant entering the compressor high or low?
A
Low pressure vapor.
6
Q
Where in a refrigerant circuit does a liquid boil to absorb heat?
A
In the evaporator.
7
Q
The refrigerant in the suction line is a gas that has been heated above its saturation. What is this condition called?
A
Superheated vapor.
8
Q
What can cause liquid refrigerant to migrate to a compressor crankcase?
A
If the compressor is located in the coldest location in the circuit
9
Q
List two conditions that can quickly damage a compressor that is starting to run?
A
Operating while in a deep vacuum or when the service valves are closed.
10
Q
What system failures require taking an oil sample?
A
A compressor burnout or if the unit has had a leak.
11
Q
Is flushing with refrigerant an acceptable tube cleaning method?
A
No.
12
Q
In addition to preventing and repairing leaks, what else should a technician do to conserve refrigerant?
A
Recover and recycle used refrigerants.
13
Q
What factors affect the speed of an evacuation?
A
Pump size, hose length, hose diameter, size of system to be evacuated, ambient temperature, suction line size, and the amount of moisture in the system.
14
Q
How should gauge set hoses be sized for use in evacuating a system?
A
Use the shortest length and the largest diameter possible for the quickest evacuation. At least as large as the vacuum pump inlet.
15
Q
When evacuating, what is the benefit of using short hoses with large diameters?
A
Reduces emissions, pressures drop, and evacuation time.
16
Q
Which connection determines the preferred size of hoses used with a vacuum pump?
A
The vacuum pump inlet.
17
Q
As the capacity and suction hose size increase, what happens to the time needed for an evacuation?
A
Time is reduced.
18
Q
What purpose is served by heating a system during dehydration?
A
To speed up moisture removal.
19
Q
Does a thorough evacuation remove moisture from a system?
A
Yes.
20
Q
What can happen to oil in the compressor if the moisture is left in an operating system?
A
The oil will form hydrofluoric and hydrochloric acids which will corrode the internal parts of the system.
21
Q
What is the result of over-evacuation a system?
A
No damage will be done.
22
Q
How can a system be leak checked using a low pressure gauge?
A
Vacuum reading will rise when vacuum pump is turned off.
23
Q
How close should the vacuum gauge be connected to the vacuum pump during evacuation?
A
As far away as possible.
24
When measuring the vacuum of a system being evacuated, the system must be isolated. What must be done to the vacuum pump?
Turn it off and valve it off.
25
What is ozone?
3 atoms of oxygen. It blocks much of the harmful ultraviolet radiation (uv-b) emitted from the sun and it keeps our earths temperature stable.
26
How much ozone can a chlorine atom destroy in the stratosphere?
One atom can destroy 100,000 ozone molecules.
27
What is Ozone Depletion Potential (ODP)?
The ability of any chemical to deplete the ozone layer.
28
What is CFC?
Chlorofluorocarbon.
29
Which refrigerants are CFC's?
R-11, 12,113,114
30
Which chemical in the CFC refrigerants does the damage to the ozone layer?
Chlorine.
31
What is an HCFC?
Hydrochlorofluorocarbons.
32
Which refrigerants are HCFC's?
R-22,123
33
Which is more harmful to the ozone layer, CFC or an HCFC?
CFC's.
34
What is it about the CFC's that make them more harmful to the stratosphere?
Chemical strength, they will not breakdown in the lower atmosphere.
35
What is an HFC?
A fluorocarbon that contains no chlorine.
36
Which refrigerants are HFC's?
R-134a, 404a, 407c, 410a.
37
What is the ODP of the HFC refrigerant?
Zero.
38
Which refrigerants contain chlorine?
CFC's and HCFC's.
39
Which refrigerants have high ODP?
CFC's.
40
Which refrigerants have low ODP?
HCFC's, HFC's are zero.
41
What is an azeotrope refrigerant?
A mixture of two or more compounds where the mixture behaves like a single chemical.
42
Is one of the components of R-500 a CFC?
Yes
43
Does stratospheric ozone help or hurt the work of the earths protective shield?
It helps
44
What chemical in the stratosphere tells us ozone depletion is occurring?
Chlorine-monoxide
45
How do we know the chlorine in the stratosphere is coming from CFC's?
The increase in chlorine and fluorine present in the stratosphere, matches the increase in emissions of CFC's.
46
How do we know CFC's get to the stratosphere?
From high altitude air sampling measurements.
47
What role does the ozone layer play in protecting the earth?
It blocks much of the harmful ultraviolet radiation (uv-b).
48
What are the effects in health from increased ultraviolet radiation?
Skin cancer, cataracts, human immunity is reduced.
49
What are the effects on the environment?
Timber growth is reduced, crop yields lowered, marine life and the food chain are impaired.
50
Is ozone depletion a problem for the United States only or a global problem?
A global problem.
51
What is the Montreal Protocol?
A treaty that called for the reduction of production of CFC's.
52
The Montreal Protocol calls for the regulation of what chemicals?
Ozone depleting compounds, CFC's, HCFC's, and Halons.
53
On what date was the production and importation of all CFC's phased out?
In the U.S., after December 31, 1995.
54
Where will we get replacements?
Through recovery of existing refrigerants.
55
What steps are called for by the Clean Air Act?
Taxes on production and use, standards set for the recovery of refrigerants.
56
What is prohibited by the Clean Air Act?
Venting.
57
Do state and local laws have priority over federal law? Can they be less strict?
No. Cities or states can create their own laws but they must be at least as strict as federal laws.
58
To prevent damage to the ozone layer, The U.S. is making laws to capture the CFC's now in use. What else does the new law do to restrict the release of CFC's?
Allows states and municipalities to create their own laws to prevent and monitor the release of CFC and HCFC materials into the atmosphere.
59
By recovering refrigerants, we ensure adequate supplies and prevent venting. What else does the recovery of refrigerants accomplish?
Prevents stratospheric ozone depletion.
60
The Clean Air Act phases out the CFC/HCFC production and prohibits venting. What else does it require?
Standards to be set for recovery of all refrigerants prior to appliance service and disposal.
61
Falsifying or failing to keep required records, failing to reach required evacuation levels and knowingly releasing CFC or HCFC refrigerants, are a violations of the Clean Air Act. What activity with a substitute refrigerant is also a violation?
Knowingly venting CFC's, HCFC's, and their substitutes
62
Which refrigerants must be recovered prior to opening a system?
All refrigerants as of 11-15-1995
63
What releases of a CFC and HCFC are violations of Clean Air Act?
Any knowingly vented refrigerants.
64
On what date did it become illegal to vent CFC and HCFC refrigerants?
July 1st, 1992
65
Which appliances are covered by section 608?
Any device which contains and uses a class 1 or class 2 substance as a refrigerant and is used for household or commercial purposes.
66
What is the primary reason the EPA requires a service aperture or process stub on all appliances?
For adding or removing refrigerant from the appliance.
67
Who sets the regulations for recovery machines?
EPA
68
What is a "self-contained" recovery machines?
A recovery machine that has its own compressor to pump refrigerant out of the system.
69
Is HCFC-123 a "low" or "high" pressure refrigerant?
Low pressure.
70
Is CFC-12 a "low" or "high" pressure refrigerant?
High pressure
71
What is the smallest container in which refrigerants may be sold to a section 608 certified technicians.
20 pounds.
72
What must you do to the refrigerant in an appliance before disposing of the appliance?
Recover refrigerant or verify that the refrigerant was previously recovered.
73
Who is responsible for removing the refrigerants from household refrigerators prior to disposal?
The final person in the disposal chain. (Scrap metal recyclers, landfill owner, etc.)
74
What is the penalty for violation of the Clean Air Act?
Fines up to $27,500 per violation per day and possible loss of technician certification.
75
How much is the bounty for information leading to a conviction?
Up to $10,000.
76
What can happen if a technician cannot demonstrate an ability to use recovery or recycling equipment?
May result in revocation of the technicians certification.
77
What is the name of the process that removes refrigerant from system and stores it without testing of processing?
Recovery.
78
What is the name for the process that removes moisture and acids from refrigerant but does not test the refrigerant?
Recycling.
79
What is the name for the process that removes moisture and acids from refrigerant and also chemically tests the refrigerant?
Reclaim.
80
What must be done with reclaimed refrigerant before it can be legally resold?
Chemically tested to ARI Standard 700, the purity level of factory new refrigerant.
81
What is the preferred instrument for detecting small leaks!
Electronic leak detector and ultrasonic detector
82
What is an inert gas typically used in leak detection?
Dry nitrogen.
83
What is typically indicates by a dehydrated system failing to hold a vacuum?
Leaks.
84
What should be done when recovering the refrigerant from a system where the refrigerant has been improperly mixed?
Recover into a separate container.
85
Can mixed refrigerant be reclaimed?
No.
86
What precautions should be taken recovering refrigerant from systems with multiple service valves?
Insure that liquid is not trapped between service valves.
87
What is the effect of low ambient temperature on the time required to complete a recovery of refrigerant?
Increases recovery time.
88
Technicians must explain to customers that recovery is necessary and it is required by law. What else should the technician tell the customer?
That all service personnel are duty bound to follow the law and protect the environment.
89
What is different about any leaks in systems charged with a blended refrigerant?
Because they are blended, the ingredients will leak at different rates.
90
What is "temperature glide"?
A family of lines depicting pressure versus temperature curve.
91
What is ternary blend?
A blend of three different refrigerants.
92
How should systems using blended refrigerants be charged?
In liquid form into the high side of the system.
93
Is there a "drop-in" refrigerant for CDC-12?
No.
94
How do you leak check an HFC-134a system with a partial charge (no HFC-134a detector available)?
Recover the remaining 134a and then pressurize the system with nitrogen and a trace charge of R-22 so you can use an HCFC electronic leak detector:
95
What is the preferred oil to be used with HFC-134a?
Ployolester
96
Can water based oils be mixed with other oils?
No.
97
What does "hygroscopic" mean?
Oil that absorbs moisture easily.
98
What lubricant is recommended for use with a ternary blend?
Depends on the blend: for HCFC's-Alkylbenze, for HFC's-Ployolester.
99
Safety glasses and butyl lines gloves should be worn for what procedures?
When operating recovery or recycling devices and when handling and refilling refrigerant cylinders.
100
What safety component must be used whenever dry nitrogen is used to pressurize a system?
Pressure regulator.
101
Safety rules for technicians such as: no open flam or hot steam near a refrigerant, never cutting or brazing a charged refrigerant line, and never using oxygen to purge or pressurize lines, are all important. Which one should a technician follow?
All of them.
102
What is Material Safety Data Sheet?
A sheet the states the safety ratings and precautions to be taken for use and handling of chemicals.
103
What safety classification within the ASHRAE standard is the most safe?
A1.
104
What is caused by the inhaling of refrigerant vapors?
Heart Irregularities or Asphyxia.
105
What is the major causes of death involving refrigerants?
Oxygen deprivation.
106
What breathing problem can be caused by CFC-12?
Asphyxia.
107
How can ice be removed from a sight glass?
With alcohol spray.
108
What must be done with a badly corroded relied valve?
It must be replaced.
109
Where can you find the allowable read pressure on a system?
Unit data plate.
110
Can oxygen be used to check for leaks? If not, why not?
No. Oxygen in the presence of oil under high pressure can be explosive.
111
What is the likely result of heating a recovery cylinder with open fame?
Refrigerant will decompose into a toxic material, venting of refrigerant in the atmosphere or the tank may explode.
112
What is the primary purpose of a disposable cylinder?
For virgin refrigerant from the manufacturer.
113
To what internal pressure should a disposable cylinder be reduced to for disposal?
Reduced to at least 0 PSIG.
114
Should you ever us a disposable cylinder for refrigerant recovery?
No.
115
To dispose of a cylinder you should be sure all refrigerant is recovered and the cylinder is no longer usable. What else should you do?
Puncture the container before disposal.
116
For safety, refrigerant cylinders should not be rusted or damaged and always properly color coded. What additional step should also be taken with these cylinders?
Properly secured at all times.
117
What is the proper color code for recovery cylinders?
Gray with a yellow top.
118
What is the maximum percent by weight that a cylinder may be filled?
80%
119
What can happen if a cylinder overfilled?
Hydrostatic pressure could cause the cylinder to explode.
120
List three methods for measuring the full level of recovery cylinder.
Floats, thermistor type sensors. And weighing scales.
121
How often must reusable cylinders be hydrostatically tested?
Every five years.
122
Why must only refillable cylinders be used for transport?
Federal code of regulations title 49 (parts 100-177) states this.
123
What must be affixed to a refrigerant cylinder prior to its shipment to reclaimer?
DOT classification tag.
124
What is the purpose of a DOT classification tag?
For transportation purposes.
125
What is the correct shipping position for a refrigerant cylinder?
I'm a vertical or upright position with their valves at the top.
126
What is the EPA definition of a small appliance?
Appliances typically charges at the factory with five pounds or less of refrigerant. Refrigerators and freezers designed for home use, room air conditioners, including window and PTAC units, package heat pumps, dehumidifiers under the counter ice makers, vending machines and drinking water coolers.
127
Does the EPA require the repair of leaks on small appliances?
Repair of leaks on small appliances is not required, but leaks should be repaired whenever possible.
128
What EPA certification type must technicians have to service any appliance that EPA calls a "small appliance"?
Type 1 or Universal.
129
What service aperture may be used on small appliance?
Access tubes or process tubes.
130
What is the name for a fitting, used to connect a recovery device to an appliance, which can close to prevent loss of refrigerant form hoses?
Low-loss fitting. (Shut-off valve)
131
What is the primary purpose for using hand valves or self-sealing hoses when using a gauge set?
To prevent loss of refrigerant.
132
Which refrigerants must be recovered under section 608 of the EPA regulations?
CFC, HCFC, and HFC refrigerants.
133
Is there a "drop-in" refrigerant for CFC-12?
No.
134
What is the replacement refrigerant for CFC-12 in household refrigerators?
HFC-134a.
135
When doing a non-condensables check, a recovery cylinder should stabilize in temperature before any readings are taken. Why?
To find the correct pressure for that temperature on a T/P chart.
136
What is the internal pressure of CFC-12 refrigerant stored at 75 deg. F?
77 PSIG.
137
What is the exception to the rule that says that someone servicing any appliance must have at least one self contained recovery machine available at their place of business?
Only when the person is working on a small appliance.
138
Ammonia, hydrogen, and water can be found in the refrigerators in some campers and other recreational vehicles. Should these compounds be recovered with EPA approved recovery equipment?
No.
139
May the nitrogen used for purging or pressurizing a system be vented to the atmosphere?
Yes.
140
May a technician use a passive recovery machine for recovery from a domestic refrigerator?
Yes.
141
What requirements are place on recovery machines built after November 15, 1993?
Must be able to recover 80% of the refrigerant is the compressor is inoperative or 90% if the compressor is operative. Must be EPA certified.
142
When using a recovery machine manufactures after November 15, 1993, what percentage of the refrigerant must be recovered in a household refrigerator with an operating compressor? What percentage of the compressor is NOT operating?
90%, 80%
143
Is a certified technician responsible for future changes in EPA regulations?
Yes.
144
What type of certification is required to purchase CFC and HCFC refrigerants?
Type 1.
145
What must be done with any regulated refrigerant vented from a graduates charging cylinder?
It must be recovered.
146
What first step must you always take before starting a recovery of refrigerant from any equipment?
Check which refrigerant is being used.
147
What is a "system-dependent" recovery machine?
System dependent recovery machines rely on the compressor of the system being serviced, or the pressure of the refrigerant to pump the refrigerant into a recovery drum.
148
Describe a system dependent (passive) recovery process for small appliances.
Evacuate or cool a cylinder. Connect the high and low hoses to the system. Pull refrigerant into the cylinder with vacuum or the low tank pressure.
149
What two conditions require that you access both the high and low side of the system for refrigerant recovery?
When there is an inoperative compressor on the system or when necessary to reach required recovery levels.
150
What are the benefits of accessing the low and high side access valves when recovering refrigerant from a system with an inoperative compressor?
It speeds up recovery, improves efficiency and may be necessary to reach requires recovery levels.
151
How should you access the system and should you run the compressor when using a system-dependent (passive) recovery on a refrigerator with an operable compressor?
Access the high side and run the compressor.
152
Which access valve (s) should you connect to when recovering from a system with an operating compressor and a completely restricted capillary tube?
High side valve.
153
When using a self-contained (active) recovery device, what two conditions can cause excessive pressure on the recovery machines high side?
A recovery container that is not properly evacuated or one that has unopened valve.
154
Why should defrost heaters be turned on during a recovery from a small appliance?
To speed up refrigerant release from the oil.
155
When should entrapped refrigerant from oil be recovered?
Any time oil is removed from a large system and on small appliances when using system dependent recovery with a non-operating compressor.
156
What does striking the appliance compressor do during a recovery?
Helps to free refrigerant that may be trapped in the oil.
157
A recovery machine should be checked daily for what?
Refrigerant leaks.
158
Can a standard vacuum pump be used as a recovery machine?
In theory yes, but unlikely. First it would have to be certifiable, second it would have to be connected to a non-pressurized recovery container.
159
Should technicians ever mix refrigerants in the field?
No.
160
How should you recover refrigerant that is different from the refrigerant you usually recover?
Different refrigerants must be placed in recovery vessels containing the same type of refrigerant.
161
What can a reclaimer do with any mixed refrigerant you ship to them?
They may either refuse to process and return it at owners expense or agree to destroy the refrigerant for a substantial fee.
162
To ship recovered refrigerant you must label the container and complete all necessary paperwork. What else should you do?
Use DOT approved cylinders.
163
What federal agency sets the standards for portable refillable tanks or containers used to ship CFC or HCFC refrigerants?
DOT.
164
Safety glasses and butylined gloves should be worn for what procedures?
When you are connecting and disconnecting hoses.
165
Piercing valves are used for what purpose?
To allow access to the sealed system for recovery.
166
On what materials are piercing valves used?
Copper or aluminum refrigerants lines.
167
What should be done to a piercing type Schrader valve after it is installed on charged system?
It should be capped after any service procedure.
168
Why should solder-less type piercing valves be removed after completion of repairs?
To prevent leaks.
169
What are the critical maintenance checks done to a Schrader valve?
Periodically checked for leaks and replaced if damaged.
170
What does a pungent odor detected after opening a system mean?
It may mean acids are present due to a compressor burnout.
171
What do you do if the oil is contaminated?
Tubing flushing might be required.
172
What system pressure would indicate a recovery should not be performed?
0 PSIG.
173
What are the current methods used to monitor the 80% fill level in a recovery tank?
Floats, thermistor-type sensors and weighing scales.
174
Why do large refrigerant leaks cause suffocation?
Refrigerants will replace air in a confined space leading to possible oxygen starvation.
175
Before entering an area of a large leak of refrigerant, what apparatus must be worn
Self contained breathing apparatus.
176
What should be done if a large leak occurs and no breathing apparatus is available?
Ventilate the space and leave the area.
177
Which acids are formed when refrigerant touches sources of high heat?
Hydrochloric and hydrofluoric acids and phosgene gas.
178
What safety component must be used whenever dry nitrogen is used to pressurize a system?
Nitrogen tanks should be equipped with regulator.
179
What information does DOT require when shipping require when shipping refrigerant cylinders?
Shipping papers must indicate the refrigerant type and number of cylinders.
180
Which government agency sets the standards for refillable refrigerant cylinders used to transport CFC and HCFC refrigerants?
DOT.
181
What component is always replaces after a system is opened for service?
Filter-driers.
182
What is the purpose of the moisture indicator in a sight glass?
To permit a check of moisture content in the system.
183
What does "back-seating" a suction valve do?
Allows flow through the main line while closing the access port.
184
What will non-condensables do to the pressures in a refrigerant circuit?
Increases discharge pressure.
185
What causes oil foaming in a system and where does it normally occur?
Oil that is mixed with refrigerant will foam in the compressor crankcase.
186
What system failures require taking an oil sample?
Compressor burnout or if the unit has had a leak.
187
A vacuum pump that is too large can cause what problem?
It can cause the moisture to freeze in the system.
188
Where is a receiver typically installed on a system?
At the outlet of the condenser.
189
What will be the boiling temperature of HFC-134a be at 0 PSIG?
-15 degrees F.
190
Is it a requirement that recovery machines contain an oil separator?
No.
191
Which refrigerant is typically used on a residential split system air conditioner?
HCFC-22
192
Is the refrigerant leaving a receiver a liquid or a gas? Is it at a high or low pressure?
Liquid, high pressure.
193
What is the initial charging method of a system when the charge is specified at 70 pounds?
Charged in liquid state.
194
Is the receiver on the high or low side of a system?
High side.
195
What is the minimum recommended capability (measures in microns) of a vacuum pump used for evacuations?
Should pull a vacuum of 500 microns.
196
What is the pressure of a CFC-12 machine at 72 deg. F while the machine is idle?
73 PSIG.
197
What is the preferred unit of measurement for checking a deep vacuum?
Microns.
198
Where is an accumulator located in refrigeration system?
On the suction line before the compressor.
199
To prevent freezing of any moisture in a CFC-12 system, valor should first be charged until the pressure is at what level?
33 PSIG.
200
What gas should be used during an evacuation to increase pressure to prevent freezing?
Dry nitrogen.
201
What is the purpose of compressor heater?
To reduce the amount of refrigerant in the lubricating oil.
202
How is moisture remaining from an evacuation removed from the refrigerant in a system?
By the filter-drier.
203
What is the preferred method of leak checking a built-up system prior to charging?
Bubble solution.
204
What would a technician initially look for during a visual inspection of a leaking hermetic system?
Stains around tubing and fittings.
205
What is typically indicated by excessive super heat on a high-pressure system?
Undercharged system, possibly the result of a leaky system.
206
Which refrigerant should be used for a trace charge during leak detection?
R-22.
207
How do you leak check an HFC-134a system with a partial charge (no HFC-134a detector available)?
Recover remaining 134a, pressurize the system with nitrogen and trace charge of R-22 so you can use an HCFC electronic leak detector.
208
For what purpose are soap bubbles used in leak checking?
For a visual check for leaks.
209
Shaft seals on an open type compressor are susceptible to what failures?
Refrigerant leaks.
210
What leak rate is permissible on industrial process refrigeration?
Effective 6/14/93, any leak rate of 35% or more on equipment with 50 lbs. of charge or more must be repaired. Less than 35% is permissible.
211
What leak rate is permissible on equipment (other than industrial or process equipment) that contains more than 50 lbs. of refrigerant?
Less than 15% annually.
212
What is the easiest way to check the type of refrigerant used in a packaged rooftop system?
By the equipment data plate.
213
Refrigerant will recover fastest in which phase, liquid or vapor?
Liquid.
214
Which refrigerant line should a recovery machine be attached to in order to recover liquid refrigerant from a system?
To the liquid line.
215
After a liquid recovery, what must be done with the vapor still in the system?
Vapor recovery must be performed.
216
Recovering in a vapor phase reduces unwanted loss of what?
Oil and unwanted contaminants from the system to the recovery machine and recovery drum.
217
On a high pressure system recovery, should the recovery cylinder be heated or cooled?
Cooled.
218
What must be done to a recovery machine when changing to a different refrigerant?
Clean out all residual refrigerant, change oil, replace filters, evacuate machine by pump-out or another machine.
219
What besides filters must periodically be charged out on a recovery machine?
Oil.
220
Recovered refrigerant can contain oil and acids. Name another compound found in refrigerants?
Moisture.
221
What is the water source for a condensing coil on a water-cooled recovery machine?
Municipal water tap.
222
What access location should you use when recovering from an air cooled system with its condenser several feet above the evaporator?
Suction line.
223
What access location should you use when recovering from a system with its condenser below the evaporator?
Liquid line.
224
Before using a recovery unit, the technician should check service valve positions and check the recovery unit oil level. What additional step must be taken?
All solenoid valves should be open.
225
What is the primary purpose for using hand valves or self-sealing hoses when using gauge set?
To prevent loss of refrigerant when connecting and disconnecting hoses.
226
What can cause recovery equipment with a hermetic compressor to overheat when drawing a deep vacuum?
No airflow over the compressor body or no suction gas flow over the internal motors, or a combination of the two.
227
What is the reason for not operating a hermetic refrigeration compressor while it is in a deep vacuum?
To prevent overheating the compressor motor.
228
What is the reason for not starting a reciprocating compressor with its discharge service valve closed?
To prevent overheating the compressor motor.
229
When can a "system-dependent" recovery device be used?
On small appliances as long as the device meets EPA standards and the technician adheres to the servicing procedures specified for the recovery equipment. Cannot be used on systems with more than 15 lbs. of refrigerant.
230
What vacuum level must you reach when recovering from a system with 38 pounds of R-502 using a recovery machine manufactured in 1995?
10 inches of Hg.
231
What is EPA's definition of a "major repair"?
Any repair that involves the removal of the compressor, evaporator, condenser, or any auxiliary heat exchanger coil.
232
Prior to making a major repair, what vacuum level must you pull when using recovery equipment manufactured in 1996 on a unit with 215 lbs. of CFC-12?
15 inches of Hg.
233
What vacuum level must you pull when using recovery equipment manufactured in 1992 when disposing of an appliance containing 12 lbs. of R-500?
4 inches of Hg.
234
Under what circumstances may a technician recover the CFC refrigerant in an appliance to atmospheric pressure only?
If leaks are in the system or if recovery to target levels would contaminate the refrigerant.
235
What procedure should be performed on an empty recovery cylinder before it is used for storing recovered refrigerant?
It must be evacuated of all non-condensables.
236
What may legally be done with refrigerant recovered from a system in order to replace a condenser coil?
Reused in the original system or transferred to another system with the same owner after it is checked so that it is free of non-condensables.
237
When servicing an operating unit with a receiver, where should he recovery hoses be attached to the unit?
To the liquid line.
238
In order to recover from a system with parallel compressors, the individual compressors must be isolated. Why
It isolates the refrigerant that must be recovered from the rest of the system.
239
Which refrigerant (s) require and equipment room monitor per ASHRAE Standard 15?
All refrigerants.
240
What protection is mandatory to protect a system against damage from excessive pressure?
A pressure relief device.
241
Are multiple relief valves connected in series or parallel?
Parallel.
242
Why is the use of a regulator required when using dry nitrogen?
To limit the outlast pressure of the nitrogen cylinder.
243
How can ice be removed from sight glass?
Cleaned with alcohol spray.
244
How high should you pressurize an idle low pressure chiller to prevent air accumulation?
Slightly above atmospheric pressure.
245
What effect does air in a chiller have on head pressure?
Raises head pressure.
246
What system failures require taking an oil sample?
A leak or major component failure (compressor burnout).
247
Why must water be circulated through a chiller during refrigerant recovery?
To prevent freeze-up of the water as pressure is reduced ok the refrigerant.
248
What is the lowest access valve on a low pressure chiller?
The evaporator charging valve.
249
Where is a centrifugal chiller's rupture disk attached?
At the evaporator.
250
What is he typical pressure setting for a low pressure chiller's rupture disk?
15 PSIG.
251
Where is he outlet of a rupture disk discharged?
Outdoor for venting.
252
How is a chiller typically charged?
Liquid through the evaporator charging valve.
253
What minimum saturation temperature needs to be achieved before liquid is barged into a chiller?
Above freezing, typically 36 deg. F.
254
To prevent freezing of water when charging a chiller, what pressure should be reached with vapor before using liquid CDC-11?
16.9 inches of Hg.
255
What could result from liquid refrigerant being charged into a chiller that is holding a 29 inch Hg. vacuum?
Can cause system water to freeze.
256
What function is served by a purge unit on a chiller?
Minimize the effects of contamination. To remove non-condensables.
257
What is the most likely cause of air leaks into a chiller refrigerant circuit?
Gaskets and fittings.
258
How is a purge unit connected on a low pressure chiller?
The inlet of the purge unit is typically connected to the top of the condenser.
259
What is a high efficiency purge unit?
It removes non-condensables that contain a low percentage of refrigerant. This adds to the value of the purge drum in refrigerant containment.
260
Shaft seals on an open type compressor are susceptible to what failures?
Refrigerant leaks.
261
Purge units work best when they are not needed. How can purge unit operating time be reduced?
By regular leak checking and repairing any leaks on a regular schedule.
262
What is the maximum pressure that can be used when leak checking a low pressure chiller?
10 PSIG on low pressure equipment that utilizes a rupture disk.
263
What is the preferred method of leak checking a charged low pressure chiller?
By increasing the refrigerant pressure using an external heat source or running hot water though the chiller tubes bit to exceed 10 PSIG.
264
Where should you check for leaks between a chiller refrigerant tube and the water box?
The chiller barrel can be emptied of all water and a leak check can be made at the drain valve with the water off. If the tubes themselves require a leak check, the check can be made with a hydrostatic tube test kit.
265
What is a hydrostatic tube test kit used for?
To check for leaks in a chiller tubes.
266
What leak rate is permissible on industrial and process refrigeration?
Effective 6/14/93, any annualized leak rate of 35% or more on equipment with 50 lbs. of charge or more must be repaired. Less than 35% is permissible.
267
What leak rate is permissible on equipment other than industrial and process equipment?
For appliances with 50 lbs. of charge or more an annual leak rate of 15% or more must be repaired. Less than 15% leak rate is permissible.
268
According to ASHRAE 3-1990, what rise is permitted in vacuum level during a standing vacuum test?
Startling at 1mm of Hg., after 12 hours the vacuum reading should not increase to more than 2.5 mm of Hg.
269
List two steps to reduce the run time of a purge unit.
Regular leak checks and repair any leaks.
270
Why should the water side of he evaporator and condenser he drained before recovering refrigerant from a chiller suspected of having tube leaks?
To prevent moisture from being drawn into the refrigerant circuit.
271
In a purge unit is operating excessively, what problem can expect to find?
Leaks.
272
What condition would cause continuous excessive moisture collection in the purge unit of a low pressure refrigeration system?
Leaks between the refrigerant circuit and the water circuit.
273
Why should oil he warmed prior to remove from a low pressure chiller?
To vaporize any liquid refrigerant that might be trapped in the oil.
274
After liquid recovery, what must be done with the vapor still in the system?
Vapor recovery must be performed.
275
Is recovery of refrigerant from a low pressure appliance typically started with liquid or vapor?
Start with liquid removal.
276
Where is the connection made for the water supply used on a water cooled recovery unit?
Local water supply.
277
What should be the maximum pressure on he discharge of a recovery machine for low pressure systems?
10 PSIG, because the rupture disk is set to open at 15 PSIG.
278
What is EPA's definition of a "major repair"?
Any repair that invoices the removal of the compressor, evaporator, confessor, or any auxiliary heat exchange coil.
279
What recovery vacuum must be met on a low pressure appliance using a machine built in 1992?
25 inches of Hg.
280
Why should you wait a few minutes after reaching the required recovery vacuum on an appliance to see if pressure rises?
To see if refrigerant is still trapped in the system.
281
Under what circumstances may the recovery from an appliance be stopped without reaching the prescribed level?
If the recovery would contaminate the refrigerant being recovered. (This level cannot exceed 0 PSIG.)
282
Is it a requirement that recycling and recovery equipment be capable of handling more than one refrigerant?
No.
283
Is it permissible to warm the refrigerant under EPA's regulations to pressurize a low pressure system to do a non-major repair?
Yes.
284
What final vacuum level is required for recovering refrigerant from a low pressure system if the technician is using recovery equipment manufactured BEFORE November 15, 1993? AFTER November 15, 1993?
25 inches of Hg, 25 mm of Hg. Absolute (equal to about 29 inches of Hg.)
285
A vacuum pump that is too large for a particular system can cause what problem?
It can cause moisture to freeze in the system.
286
How can you prevent moisture from freezing during dehydration?
You can raise the pressure with nitrogen and allow the ice to melt, then continue with the evacuation.
287
Are multiple relief valves connected in series or parallel?
Parallel.
288
ASHRAE Standard 15 covers refrigerant level monitoring for what refrigerants?
All refrigerants.
289
According to ASHRAE Standard 15, what is the standard for refrigerant concentration for a machine room that must not be exceeded without activating an alarm and starting ventilation in the machine room?
May not exceed the TLV-TWA. (Threshold limit value- Time weighted average.)
290
List four safety procedures hat should be followed when working with liquid low pressure refrigerant.
1. Use refrigerant sensors in equipment room.
2. Avoid siphoning refrigerant by mouth.
3. Wear buty-lined gloves.
4. Wear safety glasses.
291
What is the toxicity and flammability rating of HCFC-123 per ASHRAE Standard 34?
B1.
