Hvac 1 Flashcards
(256 cards)
1
Q
How long should it take to go throughthe test the first time?
A
45 minutes
2
Q
How many questions should I flag?
A
No more than 70
3
Q
What do the stars on the US American flag represent?
A
States
4
Q
How do you recognize a code question?
A
You WILL, SHALL, MUST, ONLY, MINIMUM, MAXIIMUM
5
Q
What can cause a unit to short cycle?
A
Vibration of the thermostat
6
Q
Troubleshooting questions are found in which book?
A
Modern refrigeration
7
Q
If you insulate the suction line, how will that affect the superheat?
A
The superheat will remain unchanged
8
Q
When testing a capacitor with an ohm meter, if the meter swings toward zero then slowly turns to infinity, what does that tell you about the capacitor?
A
The capacitor is good
9
Q
Where do calculations come from? Science or physics questions. Rules about installation. Which book?
A
Modern refrigeration
10
Q
How much larger should the return air be than the supply?
A
20%
11
Q
Questions about your license come out of which book?
A
Texas license laws
12
Q
If someone dies on the job site how long do you have to notify OSHA?
A
8 hours
13
Q
How long do you have to keep osha records?
A
5 years from the date of completion
14
Q
What class of fire extinguisher should be used for electrical fires?
A
Class C
15
Q
What is the toxicity of a B3 refrigerant?
A
High toxicity. Check ASHRAE refrigerant and toxicity table.
16
Q
What is the maximum permissible noise exposure level for an 8 hour day?
A
90 dBa
17
Q
What do we charge in a component before we install it in the system?
A
Gaseous nitrogen
18
Q
What’s the purpose of charging components with gaseous nitrogen?
A
Keeps them clean and dry until they’re ready to install
19
Q
What is Phosgene Gas?
A
A by-product of some refrigerants when they are exposed to an open flame or extreme heat.
20
Q
How many times should I read through all my tabs?
A
- Spend 8 hours at a minimum and read all the tabs at least 3 times.
21
Q
What does delta mean?
A
Difference
22
Q
Where would you find the formula for calculating the change in heat?
A
Sensible Heat tab in the modern refrigeration book
23
Q
What is the latent heat of vaporization?
A
The latent heat added to a liquid to change it into a gas, or the latent heat removed from a gas to change it into a liquid.
24
Q
What do you call the latent heat added to a liquid to change it into a gas?
A
Latent heat of vaporization
25
What is a Capillary Tube?
A metering device consisting of a length of seamless tubing with a small and precisely formed inside diameter
26
Which of the following metering devices on a refrigeration system can not be adjusted?
Capillary tube
27
Where do you go if the question is asking for a definition or a word, where do you go?
Definition/Glossary section, not the index.
28
When the high side and low side pressures equalize, what position is the compressor in?
The compressor is stopped
29
What are the types of refrigeration lubricants?
MO, POE, AB and PAG
MO - mineral oils
POE - Polyol ester
AB - alkylbenzene
PAG - polyalkylene glycol
30
What do most new azeotropic mixtures use for refrigerant lubricants?
Polyol Ester (POE) lubricants
31
What do traditional refrigerants use for lubricants?
Mineral Oil
32
What type of refrigerant lubricant should be used for 410a
POE
33
What is the atmospheric pressure at sea level?
14.7 psia or could be listed as the next closest whole number which is 15
34
You should repair a leak in a refrigeration system within 30 days if it has how many lbs of refrigerant, AND has yearly leak rates at or above what trigger levels?
GREATER THAN 50 lbs
If commercial or industrial, 35%
If comfort cooling and other appliances, 15%
Does not apply to refrigeration systems with less than 50 lbs of refrigerant
35
What is the trigger level to repair commercial and industrial refrigeration systems?
35%
36
What is the annual leak trigger level to repair comfort cooling and other appliances?
15%
37
38
When can reclaimed refrigerant be installed in a system other than the one you removed it from?
When it’s the same owner
39
Where can you reinstall recovered refrigerant?
In the same unit in was removed from
40
What is subcooling?
The amount of heat removed from a refrigerant after it has condensed
41
Subcooling is typically designed to be how many degrees?
Between 10 - 20 degrees
42
What is Superheat?
The amount of heat added to a refrigerant after it has evaporated.
43
If you have a 95 degree dry bulb temperature and a 66 degree wet bulb temperature, what is your target Superheat?
10 degree target superheat
44
When using a recovery cylinder, it should not be charged more than what percent of its capacity?
80% of the water capacity
45
During brazing, arrange for a continuous low pressure flow of what to pass through the part of the system being brazed?
Nitrogen
46
When brazing, how much nitrogen pressure should you apply to pass through the part of the system being brazed?
1-2 PSI
47
What does purging a system with Nitrogen do when brazing?
It prevents oxides from forming inside the tube
48
If the primary coil has 100 turns and the secondary coil has 50 turns, on a step down transformer, the voltage exiting the transformer will be _____________ of the voltage entering the transformer.
Half
49
On a step down transformer with the primary coil having 100 turns and the secondary coil having 50 turns, if the voltage entering has 120 volts what would be the voltage going out?
60
50
What is the smallest commonly used wire size in HVACR?
18 AWG
51
HVACR equipment is designed to operate in a range of ___________ of its rated voltage? (I.e. something like a motor)
+/- 10%
52
When a capacitor must be replaced you should use the same capacitance value of the capacitor being removed. If the same capacitance value is not available, up to _______________ capacitance is allowed.
10% Greater
53
What is a rectifier?
An electronic circuit that converts AC to DC
54
What is an inverter?
An electronic circuit that converts DC to AC
55
A _____________ converts AC to DC.
Rectifier
56
A _____________ converts DC to AC
Inverter
57
Which of the following motors produce a high starting torque
CSCR (Capacitor Start Capacitor Run)
58
How can a technician wire a 3 phase motor in series to use a 480v power supply or in parallel for a 240v power supply depending on the electrical service available?
using jumper wires
59
What is rated voltage?
The voltage level where the motor will perform at its best. Also known as nameplate voltage.
60
What is a hermetic compressor motor?
A motor sealed inside a compressor dome along with the compressor’s mechanical parts
61
When does a high pressure motor control actuate or operate?
At 20% above normal head pressure
62
What does a high pressure motor control do?
It protects the compressor from the dangers of high pressure and high temperature. It also protects the compressors motor from overheating and overloading.
63
What is cemf?
Counter Electromotive Force
64
The operation of a potential relay is based on increasing voltage in the form of __________?
cemf ——counter electromotive force
65
What is similar to a contactor but has a built in overload protection?
A motor starter
66
When using a volt meter, the volt meter should be connected how when regards to the power or load?
in parallel
67
Which meter is used to measure the electrical resistance in a circuit?
Ohm meter
68
An ohm meter can be used to detect the following?
A short or open circuit?
69
How is an in-line ammeter connected to the load being tested?
In line or in series
70
Which of the following meters can be used to determine the wattage consumed or used by an electric motor?
A Wattmeter
71
When would you use a ladder diagram?
When troubleshooting electrical circuits
72
When would you use a pictorial diagram?
When tying to locate devices within the unit and properly wire the unit
73
Which type of diagram is used to troubleshoot electrical circuits?
Ladder
74
Which diagram is more useful to locate devices within the unit and properly wire the unit?
Pictorial diagram
75
When using an ohm meter to test a capacitor, if the meter swings toward zero and slowly returns to infinity, the capacitor is _________.
Good
76
Widening the groove allows the belt to ride closer to the hub which does what to the speed of a belt driven blower or fan?
Reduces it
77
Belt size is always determined by their _________ length?
Outside
78
A system will short cycle if the thermostat is not mounted securely and is exposed to what?
Vibration
79
When wiring a thermostat, what is the Rc terminal for?
Cooling power
80
When wiring a thermostat, what is the Rh terminal for?
Heating power
81
When wiring a thermostat, what is the R terminal for?
Power
82
What is the advantage of a direct expansion evaporator?
It prevents large amounts of liquid refrigerant from pooling in the evaporator
83
84
The temperature differential between the inlet and the outlet water of a chiller should be about what?
About 10 degrees F
85
If you can’t put your swinging vane anemometer directly in the air stream, what could you use to remotely measure that?
A Pitot tube
86
Static air pressure is based on what?
The density of the air
87
When installing a filter designed to filter out smoke, what micron filter should be used?
0.1
88
How do you measure air drop?
By using a manometer
89
What does a manometer do?
Measure pressure drop across a filters in inches of water
90
What can be used to measure pressure drop across the filters in inches of water?
Manometer
91
When a system is in cooling mode it should provide at least how many cfm of air per person?
15
92
To minimize turbulence and maximize airflow, make any directional changes in the ductwork how?
As gradual as possible
93
When a blower is on medium speed and you have an external static pressure of 0.4 in. WC (water column), what is your cfm?
1318
94
What do we use to test pressure drop?
A Manometer
95
Heat always flows from how/where?
Hot to cold
96
Heat always flows from where?
A warmer environment to a cooler environment
97
For the purpose of sizing an HVAC system, the maximum heat load is determined for a period of how long?
1 hour
98
What ACCA (Air Conditioning Contractors of America) manual is used for Residential Load Calculations?
Manual J
99
What ACCA (Air Conditioning Contractors of America) manual is used for Commercial Load Calculations?
Manual N
100
What is the indoor design temperature (IDT) that a unit is sized to generally set to?
70 or 72 degrees
101
What is the R value of a 4” thick concrete slab with no finish?
1.54
102
What is the U value of a 4” thick concrete floor with no finish?
0.65
103
Define heat transfer rate
The amount of heat conducted through a structure for a given unit of time
104
What is the formula for calculating het transfer using U-values?
Q = (U x area) x (To — Ti)
105
What’s the formula to calculate or convert R and U values?
1 / (divided by)
106
Can you add R values? (I.e. R1 + R2 + R3)
Yes
107
Can you add U values? (U1 + U2 + U3)
No
108
What is one of the best ways to prevent unwanted infiltration?
Provide positive air pressure
109
What is often provided inside a furnace blowers door or furnace blower access panel?
Safety interlock switch
110
Where is the safety interlock switch often located on a furnace?
Inside a furnace’s blower access door or panel
111
What is a by-product of incomplete combustion?
Carbon monoxide
112
What causes a yellow tip on a flame?
Incomplete combustion or lack of air
113
How many btu’s would be produced by the combustion of 1 cu ft of propane?
2500 btu’s
114
If I wanted to combust 1 cu ft of propane, how many cubic feet of air do I need?
24 cu ft
115
Where are you never allowed to install LP or propane equipment?
A PIT or a basement where gases may collect.
116
What is the permissible parts per million of carbon monoxide in natural gas?
LESS THAN 50 ppm
117
The gas pressure for natural gas should be what?
3.5 in. WC (water column)
118
When do I need to make a burner orifice adjustment? At how many feet of elevation?
OVER 2,000 ft of elevation
119
On a heat pump thermostat, what is the O terminal for?
Cooling mode reversing valve
120
On a heat pump thermostat, what is the O/B terminal for?
Reversing valve
121
Heat pump defrost controls are typically initiated by what 2 things?
Time and temperature
122
Most walk in cabinets now use what kind of insulation?
Foamed in place insulation made of rigid polyurethane
123
Insulation in a walk in cooler is usually how thick?
4 inches
124
125
The Stirling cycle, when used in a three-stage system, can produce temperatures as low as what?
- 450 degrees F. (NEGATIVE)
126
In a screw compressor, the male rotor rotates how in regards to the female rotor?
50% faster
127
When adjusting a TXV it should not be adjusted more than how much at a time?
1/4 turn
128
When adjusting a TXV, how long should you wait before making another adjustment?
10 - 15 minutes
129
Where is an externally equalized expansion valve installed?
Just below the diaphragm
130
An equalizer should be used if the pressure drop between the inlet of the evaporator and the outlet is how much?
MORE THAN 4 psi
131
The sensing bulb must be in good thermal contact with the what?
Evaporator outlet
132
What happens if a TXV is too big (oversized)?
The valve will hunt, or surge
133
What happens if a TXV is too small (undersized)?
The evaporator will be starved
134
What limits the high current necessary for the compressor motor to operate?
Crank case pressure regulator
135
TXV sensing bulbs should be mounted at what position if they’re larger than 7/8”?
Eight o’clock and four o’clock
136
At what temperature will the color change element in a moisture indicator change temperature?
275 F or higher
137
What can we do to avoid a moisture indicator from overheating?
Install a cold pack
138
What is the most common non-condensable that gets trapped in a refrigeration system?
Air
139
As water velocity and temperature difference increase, the heat transfer rate also increases. For this particular evaporator, if the water velocity is reduced from 250 rpm to 150 fpm, the cooling capacity of the evaporator is reduced by what?
About 30%
140
How much larger should the liquid receiver be than the total volume in the system?
15% of the liquid volume
141
What is the purpose of installing a trap on a suction line?
It prevents a large slug of oil from returning to the compressor during the system start up
142
If I have a 60,000 btu per hour, also known as a 5 ton per hour system, if I’m going to run 50 ft what’s the minimum size of the discharge line?
3/4
143
How many grains are in 1 lb?
7000 gr
144
According to the EPA, a type I certification is allowed to work on small appliances. Small appliances is defined as what size?
5 lbs or less
145
What is an accumulator?
A storage tank in the suction line that collects liquid refrigerant from the evaporator and suction line and prevents I from flowing farther along the suction line before vaporizing.
146
What is ambient temperature
The temperature of the air surrounding an object
147
What is Boyle’s law?
A gas law describing the inverse relationship between pressure and volume, provided temperature remains constant
148
What is the Clean Air Act (CAA)
A US federal law that seeks to limit ozone depletion and air pollution
149
What do you call a heavy duty relay that can handle high-current loads?
A Contactor
150
What do you call the tube used to carry refrigerant vapor from the evaporator to the compressor?
Suction line
151
Repeated bending or hammer will cause the copper to what?
Work harden
152
A 100 watt light bulb will generate ____________ BTU’s in per day
8194
153
154
12” x 14” duct moves _____ CFM at a velocity of 150 FPM.
174
155
A 3/4 horsepower motor will produce _____ BTU’s per day
45,820
156
A length of flex duct measuring 10ft when fully stretched is installed between 2 duct connections 7 ft apart. What percent compressed would this be?
30%
157
How long do you save the OSHA 300 Log, the privacy case list (if one exists), the annual summary, and the OSHA 301 Incident Report forms?
5 years following the end of the calendar year that these records cover
158
What is the minimum size of a condensate drain line?
3/4”
159
A high pressure boiler is a boiler furnishing steam at what pressure?
A. 5 psi
B. 10 psi
C. 15 psi
D. 20 psi
Answer is D because the rule book says pressure is in excess of 15 psi
160
What do you call a metal connector for medium and high heat appliances?
Breeching
161
Which one of these would be considered a confined space?
A. 45
B. 50
C. 55
D. 60
A. 45
Because a confined space is defined as a room or space having a volume LESS THAN 50 cubic feet
162
At what temperature am I brazing?
At a temperature of greater than 840 degrees
163
At what temperature am I soldering?
Up to and including 840 degrees
164
What is the maximum pressure of a steam heating boiler?
15 psi
165
What is the maximum allowed output temperature of a water heater?
210 degrees
166
A brazing alloy with 45% silver content starts flowing at what temperature?
1145 F
167
A brazing allow with 45% silver content starts melting at what temperature?
1120 F
168
What is Pascal’s Law?
Pressure applied upon a confined fluid is transmitted equally in all directions.
169
What is Boyle’s Law?
The volume of gas varies inversely to the pressure, provided the temperature remains constant
170
What size platform is required when working on appliances in attics and under floor spaces?
30 x 30
171
When accessing appliances on the roof, how much clearance shall be available between the access opening and the edge of the roof?
6 ft
172
When servicing appliance on a roof, if the access between the opening and the edge of the roof is less than 6 ft, how tall should the rails or guards be at?
42”
173
A nail salon has an area of 800 sq ft. According to the IMC, how much exhaust airflow is required for the space?
480 CFM
174
For ducts conveying explosives or flammable vapors, how far must the exhaust be from a property line?
30 ft
175
For ducts conveying explosives or flammable vapors, how far must the exhaust be from operable openings into buildings?
6 ft
176
For ducts conveying explosives or flammable vapors, how far must the exhaust be from exterior walls and roofs?
6 ft
177
For ducts conveying explosives or flammable vapors, how far must the exhaust be from combustible walls and operable openings into buildings that are in the direction of the exhaust discharge?
30 ft
178
For ducts conveying explosives or flammable vapors, how far must the exhaust be from the adjoining grade?
10 ft
179
What type of refrigerant is R410A?
HFC
180
When adding a bonding jumper to gas piping, what is the minimum copper wire size
6 AWG
181
According to the IMC, joints and connections of condensate lines shall be made in accordance with the applicable provisions of what standard?
The IPC (International Plumbing Code)
182
For unlisted appliances having draft hoods, the thimble shall be not less than what size?
Not less than 6” larger in diameter than the metal pipe
183
According to the IMC, exhaust ducts for clothes dryers shall be supported at what intervals?
Every 4 ft
184
According to the IMC, transition ducts for clothes dryers shall not be greater than how many feet?
8 ft
185
According to the UMC, what is the maximum length of a clothes dryers exhaust duct?
14 ft, including 2 of the 90 degree elbows. A length of 2 feet shall be deducted for each 90 degree elbows in excess of 2.
186
To calculate exhaust duct length, where do I go?
IMC page 5-10
187
Attics containing appliances shall bear provided with an opening not less than what size?
30” high and 22” wide
188
Appliances in attics are required to have a level service space not less than what size at the front or service side of the appliance?
30” x 30”
189
When combining spaces on the same story, each opening shall have a minimum free area of how much?
1 sq in per 1,000 BTU’s, but not less than 100 sq inches
190
When combining spaces on the same story, each opening shall have a permanent opening within how far of the top and bottom of the enclosure?
12” of the top and bottom
191
When combining spaces on the same story, the minimum dimension of air openings shall not be less than how much?
3 inches
192
A 120v electrical receptacle shall bear provided located within how many feet of the equipment for service?
25 ft
193
Pressure vessels having an inside dimensions of 6” or less shall be protected by what?
A pressure relief device or fusible plug
194
If a refrigeration system uses 2,888,000 BTU’s in a 24 hour period, what tonnage is the system?
10 ton
195
What is the most common type of ACR copper tubing used?
Type L
196
Where a closet is designed for the installation of a clothes dryer, an opening of not less than how many square inches for makeup air shall be provided in the door or by other approved means?
100 sq in
197
What is the spacing for hanging copper refrigerant lines? Or steel pipe for gas?
Check UMC pg 34
Copper - Horizontal lines 1 1/2” and smaller, 6 ft. 2” and larger, 10 ft. Vertical, each floor not to exceed 10 ft
Steel pipe for gas -
198
What is the toxicity and safety classification of R-32 refrigerant?
A2L
199
According to the IMC, what is the maximum length of a clothes dryers exhaust duct?
35 ft from the connection to the transition duct from the dryer to the outlet terminal
200
According to the UMC, transition ducts for clothes dryers shall not be greater than how many feet?
6 ft
201
A system in a cooling mode should provide at least how many cfm’s of air per person?
AT LEAST 15
202
How do you calculate the required air exchange rate?
Number of occupants x 15 cfm
203
Brazing alloy with 45% silver content STARTS FLOWING at what temperature?
1145 F. (And starts melting at 1120 F)
204
What type of refrigerant is R410A?
HFC
205
When adding a bonding jumper to gas piping, what is the minimum copper wire jumper size?
6 AWG
206
Makeup air supply locations in a machine room shall be positioned relative to the exhaust air locations to avoid what?
Short circuiting
207
For appliances on the roof, how much clearance shall be available between the access opening and the edge of the roof?
6 ft
208
Appliances in residential garages and in adjacent spaces that open to the garage and are not part of the living space of a dwelling unit shall be installs so that all burners and burner ignition devices are located not less than how far above the floor?
18 in
209
Condensate lines should be drained to where?
Approved plumbing fixture or disposal area
210
Condensate or wastewater shall not drain over what?
A public way
211
The condensate drain line should be physically discharged where?
Somewhere readily observed
212
To install a clothes dryer in a closet, how big should the opening be for makeup air in the door?
Not less than 100 sq in
213
At what angle are grease filters supposed to be installed in a hood?
Vertical, meaning not less than 45 degrees from the horizontal.
214
What is the minimum gauge steel of a type II hoods shall?
Not less than 0.024 gauge
215
Hoods constructed of copper shall be of copper sheets weighing not less than how much per sq in?
0.17 ounces per sq inch
216
Hoods constructed of copper shall be of copper sheets weighing not less than how much per sq ft?
24 oz per sq ft
217
What’s the minimum clearance your ducts have to be off the ground if they’re made out of anything other than plastic?
NOT LESS THAN 4 inches
218
Metal ducts have to be supported every time they do what?
change directions
219
What is the maximum temperature you can dump through a FLEX DUCT?
250 degrees
220
When using an underfloor space as a supply plenum, what size access opening shall be required?
24 x 24
221
When using the under floor space as a supply plenum in a house, what is the maximum allowable outlet air temperature?
200 degrees
222
Automatic shutoff shall be accomplished by interrupting the power source of the air moving equipment upon detection of smoke in the where?
Main supply air duct
223
Air moving systems supplying air to enclosed spaces within a building shall be equipped with an automatic shutoff when supplying how much air to that space?
MORE THAN 2000 cfm
224
What is the MINIMUM standard method for combustion air?
50 cubic feet per 1000 BTU’s
225
What is the minimum dimension of a combustion air opening?
Not less than 3 inches for both indoor and outdoor
226
What is the minimum area of an indoor combustion opening?
100 sq in
227
What’s the minimum dimensions of an indoor combustion opening?
3 inches
228
Where instructions are not available, what is the minimum clearance required in the back of a refrigerator?
2 inches
229
Manually operated dampers ___________ be installed in combustion air openings
Shall not
230
What is the minimum thickness of a galvanized steel vent connectors for a 6” diameter connector?
.023 inches
231
What is the minimum slope for a vent connectors
At least 1/4” per foot
232
What is the maximum horizontal length of a single wall vent connectors?
75% of the height of the chimney or vent
233
What kind of vent does a wall furnace require?
B-W
234
What’s the minimum distance a floor furnace shall be off the ground?
6 inches
235
What kind of a vent does a wall furnace require?
Type B-W
236
How much clearance should be around a floor furnace?
12” from all sides except the control side which is 18”
237
On a suspended type room heater, it should be supported to damp out excessive amounts of what?
Vibration
238
239
On a unit heater, what shall hangers and brackets be constructed of?
Noncombustible material
240
For an infrared heater, how much ventilation is required?
At least 4 ft
241
What 2 things will is every installer supposed to provide on every boiler installation?
Control diagram and operating instructions
242
Who’s supposed to provide a control diagram and operating instructions when a boiler is installed?
The installer
243
A furnace supplying warm air to under-floor space shall be equipped with an automatic control that will start the fan that circulates the air when?
When the air in the furnace bonnet reaches a temperature not exceeding 150 degrees
244
What is the maximum temperature a furnace can supply air to a plenum that is located under the floor?
200 degrees
245
If I have a room containing a condensing unit, I need enough ventilation to change the air in that room how often?
Every 20 minutes
246
If I have a room containing a condensing unit, I need the air to be completely changed how many times per hour?
3 times per hour (every 20 minutes)
247
Where can a condensate line be drained to?
An approved location
248
In a refrigeration machinery room, what size must the door be to get into the room?
36 x 80
249
What size passageway is required for a refrigeration machinery room?
36 x 80
250
I need to be able to approach how many sides of the equipment in a refrigeration machinery room?
Not less than 2 sides
251
What type of emergency shut off switch is required for a refrigeration machinery room?
break glass type or with an approved tamper resistant cover
252
Where is the emergency shut off switch located of a refrigeration machinery room?
Outside the principal refrigeration machinery room entrance
253
What is the maximum distance between supports on a refrigeration lines following the 2nd bend?
2 ft
254
In a heat pump, when the system is in heat mode, where is the extra liquid refrigerant stored?
In the charge compensator tank
255
Where do we want the pressure relief device on a positive displacement compressor?
In the discharge line between the compressor and the stop valve
256
What tool measures wind speed and direction?
Anemometer
