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Hvac > old > Flashcards

old Flashcards

1
Q

Bonnet

A

Top cover, often removable. Connects the valve operator to the movable valve disk assembly

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2
Q

Valve operator

A

Any device used to move the stem valve disk assembly

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3
Q

Globe valve has high or low pressure difference

A

High

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4
Q

2 types of three way valves

A

Diverting and mixing

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5
Q

What are 2 applications that use reversing valves

A

Heat pumps and defrost controls

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6
Q

ASHRAE

A

American Society of Heating Refrigeration and Air conditioning Engineers

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7
Q

Flammability levels of refrigerants

A

1-3 no flammability to high

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8
Q

Toxicity levels of refrigerants

A

A or B low or high toxicity

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9
Q

Due diligence

A

Took all reasonable steps for prevent a comission

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10
Q

Which code prevails if they conflict?
Appliance installation or government

A

Government

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11
Q

Do you need certified appliances when placed in mobile homes?

A

No

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12
Q

What must you do with defective heat exchangers in residential and commercial?

A

Can be repaired temporarily but must be replaced in residential.
Can be repaired upon certification in commercial.

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13
Q

Maximum allowable pressure drop on a low pressure system (7-14”WC)

A

1”WC

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14
Q

Rough in piping

A

Between the meter and finish piping

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15
Q

Maximum allowable pressure drop on a high pressure system (above 14”WC)

A

50% standing pressure

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16
Q

When making an extension gas line, where can you connect the extension

A

Within 2 ft of the gas meter of the existing piping

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17
Q

Can you install gas lines in stairwells

A

No

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18
Q

Teflon tape must be applied wrapping it _, with _% overlap, and leaving the first _ starter threads bare

A

clockwise, 50% overlap, first 2 starter threads

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19
Q

What’s the min depth of dirt pockets

A

3”

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20
Q

What type of control system are bimetal strips

A

Electromechanical

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21
Q

What’s an ORI and CRO

A

Open on rise in inlet
Close on rise in outlet

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22
Q

What’s the difference between cut in and cut out in temp control

A

Controller differential

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23
Q

What are the 2 terms for the difference between the controller temp setpoint and the control point (measured temperature).

A

Overshoot and undershoot

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24
Q

Deviation

A

The time it takes for the control point (measured temp) and the set point to equalize

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25
Q

Offset

A

The sustained difference between the control point and the setpoint

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26
Q

Differential

A

The difference between cut in and cut out temps

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27
Q

The OFC stops the compressor because there is no oil in the head but there is not leaks, should you add oil?

A

No

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28
Q

Contactors normally have both NO and NC contacts

A

FALSE

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29
Q

When should you use a contactor vs a relay

A

Contactors for more than 15A

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30
Q

Mullion heater

A

Doorframe heater

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31
Q

Compressors that have _ use oil failure controls

A

Oil pumps

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32
Q

What must you do to thermostats before mounting them.

A

Level them

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33
Q

What’s one of the most common applications for flexible diaphragm sensors

A

Combustion aiproving control

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34
Q

Oil failure control

A

Senses the differential pressure by sensing the difference between the crankcase and oil pump pressure

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35
Q

Hygroscopic sensors

A

Electromechanical devices that consists of organic materials that absorb and releases moisture

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36
Q

Humidistats close on (rise/fall) in RH

A

Fall

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37
Q

Enthalpy controllers

A

Measure actual beat content in the ambient air

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38
Q

Transformer

A

Induces a secondary alternating current with use of coils of varying amounts

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39
Q

Relays or contactors can be repaired

A

Contactors

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40
Q

Electromechanical TDR (time delay relay)

A

Energizes a resistive heater to switch at least 1 bimetal after a predictable time

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41
Q

Overload devices

A

Protects end use devices. Either line duty or pilot duty

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42
Q

Line duty

A

Interrupts current to the motor

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43
Q

Pilot duty

A

Interrupts a control system by opening another control system such as a contactor or relay
(Solenoid valve <-> refrigerant system)

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44
Q

Overcurrent devices

A

Protects conductors from excessive current

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45
Q

Magnetic overcurrent device

A

Usually an underpowered NC contactor that energizes when excessive current causes it to open

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46
Q

Low ambient limit thermostats are often used how?

A

To prevent the compressor from starting at low temps

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47
Q

What do change-over thermostats and enthalpy controllers do

A

Function as a low ambient temperature limit and change to free cooling from the economizer cycle

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48
Q

What are mixed air thermostats

A

Proportional temperature controllers that modulates the dampers of an economizer

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49
Q

Freezestats

A

Evap low limit thermostats, prevent the system from running when the evaporator is too cold. Safety

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50
Q

What’s used to interrupt a roll out

A

Rollout limit

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51
Q

What’s used to interrupt a backdraft

A

Spill limit

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52
Q

What class and symbol of fire extinguisher should be used for electrical fires

A

Class C blue circle

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53
Q

What is the ratio for ladder placement

A

4:1

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54
Q

What percentage of OHS injury claims were musculoskeletal?

A

67%

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55
Q

What percentage of all work related injury claims involved the back?

A

37%

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56
Q

How far should extension ladders overreach the top

A

1m/3ft/3 rungs

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57
Q

What is a type 1A ladder

A

Extra heavy duty ladder rated for 300lbs

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58
Q

What are the cons of Aluminum ladders?

A

It’s electrically conductive

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59
Q

What is the ratio for scaffolds

A

3:1

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60
Q

What must be installed on any scaffolds?

A

Guardrails 0.92-1.07m

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61
Q

What are outriggers

A

Side extensions that add lateral stability to the scaffold

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62
Q

What’s a type of natural fibre for ropes

A

Number One Grade manila

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63
Q

What’s the refrigeration code called

A

B52-5

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64
Q

How many sections are there in the refrigeration code

A

15

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65
Q

LFL

A

Lower flammability limit

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66
Q

TLV-TWA

A

Threshold limit value - Time weighted average

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67
Q

Annexes

A

Provides information to the overall code and archived code

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68
Q

Zeotropic

A

Blend of different refrigerants with varying saturation

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69
Q

What are some factors that affect the probability of arc faults

A

Condensate, equipment failure, corrosion, dust, over voltage

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70
Q

Factors affecting the severity of an arc flash

A

Proximity of the worker
Amount of heat from the arc flash
Exposure time

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71
Q

What code book determines arc flash safety

A

Z462

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72
Q

What clothing material shouldn’t be worn when dealing with electrical

A

Synthetic

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73
Q

What is the code for Mechanical refrigeration code book and who developed it

A

B52-5 by the Alberta Boilers Safety Association

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74
Q

What refrigerants and systems does B52-05 not apply to

A

Water and air, systems connected to railcars, airplanes, motor vehicles, ships

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75
Q

Superheating

A

Adding heat when the refrigerant is at a temperature which exceeds that of saturation (vapour) at the same pressure

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76
Q

Subcooling

A

Removing heat when the refrigerant is at a temperature which is below that of saturation (liquid) at the same pressure

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77
Q

What is the typical temperature difference of superheating and subcooling. And where at what distance?

A

15°F 6” out the evaporator and 10°F 6” out the condenser

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78
Q

IDLH

A

Immediate Danger to Life or Health

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79
Q

How many joules does it take to heat 1kg of water by 1°C?

A

4.2kJ

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80
Q

What is specific heat (c)?

A

The amount of energy required to change the temperature of a substance by 1°C

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81
Q

How is British thermal unit defined?

A

The amount of heat required to heat 1lb of water by 1°F

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82
Q

What are the 2 laws of thermal dynamics?

A

First law: energy cannot be created or destroyed
Second law: heat moves from high to low heat

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83
Q

Desuperheating

A

Removing heat from the superheated hot refrigerant gas down to the condensing temperature.

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84
Q

What are the three methods of heat transfer

A

conduction, convection, radiation

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85
Q

back pressure

A

the low side pressure of a refrigerant system

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86
Q

head pressure

A

the high side pressure of a refrigerant system

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87
Q

head, static

A

Fluid pressure based on the height of a column of fluid.

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88
Q

sublimation

A

solid to gas

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89
Q

Ton of Refrigeration

A

The amount of heat necessary to completely melt one ton of 32 deg. F ice in 24 hours. (200 BTUs per minute or 12,000 BTUs per hour)

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90
Q

Threshold limit value (TLV)

A

Refers to airborne concentrations of refrigerant and represents conditions under which it is believed that nearly all workers may be exposed to without adverse effect

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91
Q

positive displacement

A

Class of compressors that increase pressure by squeezing.

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92
Q

centrifugal/non-positive displacement

A

Class of compressors that increase pressure by using centripetal force and speed.

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93
Q

What must rotary and scroll compressors must have

A

check valves

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94
Q

Pollutant of electronic air cleaning

A

Ozone gas

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95
Q

ASHRAE

A

American society of heating, refrigeration, air conditioning engineers

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96
Q

Three categories of filters

A

Dry, wet and electronic

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97
Q

IAQ

A

Indoor air quality

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98
Q

PM

A

Preventive maintenance

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99
Q

Sick building syndrome

A

Legionnaire syndrome

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100
Q

Glide

A

Range of saturation temperature for a zeotropic refrigerant

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101
Q

Def of heat vs temperature

A

Heat: energy of molecular (kinetic) motion
Temperature: average amount of molecular motion

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102
Q

The amount of energy an object has depends on what

A

It’s composition and size

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103
Q

What current can cause heart failure

A

100mA-200mA

104
Q

What are ohmmeters?

A

Inserted around a resistive element (NON-POWERED) to measure resistance

105
Q

What safety measures should be followed before using the ohmmeter on the system?

A

Remove the power sources

106
Q

What is the three-step voltage test

A
  1. Test the meter to a known voltage
  2. Test the equipment
  3. Test the meter again
107
Q

How many keys must there be to open the lock during lockouts?

A

1

108
Q

Uses for CAT III rated electrical metering instruments

A

600V or less building distribution systems, located after the utility company connection

109
Q

Uses for CAT IV rated electrical metering instruments

A

Utility connections and power lines

110
Q

What is the r.m.s voltage?

A

The value of direct voltage that produces the same power as the alternating voltage.

111
Q

What are the 2 plates in a battery.

A

Anode and Cathode

112
Q

How many electrons are in a Coulomb

A

6.28x10¹⁸

113
Q

What is conventional flow and electron flow?

A

Conventional current is positive to negative, and electron flow is the flow of electrons from negative to positive

114
Q

You can apply pressure to what kinds of materials to produce EMF

A

Crystals of bone, wood, metal, or minerals

115
Q

What does Ohm’s law state?

A

The current in a circuit is directly proportional to the emf and inversely proportional to the resistance

116
Q

What’s the effect of producing electricity from pressure?

A

Piezoelectric effect

117
Q

The energy lines that magnets emit are called

A

lines of magnetic flux

118
Q

When a conductor crosses a magnetic field, what is this process called

A

Electromagnetic induction or generator action

119
Q

Faraday’s law of induction

A

The magnitude of the voltage induced is proportional to the rate at which the conductor cuts the lines of magnetic flux

120
Q

What are the 2 ways electrostatics are used in HVAC/R

A

In air filtration with precipitators and with power coating painted surfaces on equipment

121
Q

Magnetic domain

A

When all the magnetic moments in a group of atoms align.

122
Q

Cathode and anode

A

Positive and negative plate in a battery

123
Q

Connecting various electrodes in different configs can what

A

Create batteries of different voltages

124
Q

Permeability

A

Ability of a material to concentrate magnetic flux

125
Q

Reluctance

A

A materials resistance to magnetic flux.
Opposite of permeability

126
Q

Magnetic saturation

A

When the magnetic material cannot be magnetized any further

127
Q

Inductance

A

Current in a circuit creates a voltage that opposes the change in current

128
Q

How many degrees is one alternation

A

180°

129
Q

What’s one cycle of electrical generated

A

Cutting across 1 pair of N S pole.

130
Q

What angle of sine wave is used to calculate RMS value

A

45°

131
Q

What’s effective AC value

A

RMS value, or value read from multimeter

132
Q

3 factors making up impedance in AC circuit

A

Resistance, inductive reactance, and capacitive reactance

133
Q

Inductance opposes any change of
Capacitance opposes any change of

A

Inductance opposes current
Capacitance opposes voltage

134
Q

Example of process plant

A

The furnace, heat exchanger

135
Q

What does the comparator in the controller do?

A

Compares the value of the controlled variable and the set point

136
Q

What is the controlled medium?

A

The process material in the control system in which the variable to be controlled exists e.g. the air

137
Q

What is the controlled variable?

A

The measurement of the controlled medium e.g. temp of the air

138
Q

Final Control Element

A

a controlled device that receives its signal from a controller and meters the flow of the control agent

139
Q

RGYWC

A

Red - hot wire
Green - Blower motor
Y (blue) - cooling
W (black) - heat
C (white) - common

140
Q

What are the 3 most common proportional analog signals?

A

0-10V DC
2-10V DC
4-20mA DC

141
Q

actuator

A

An actuator is a device that converts a pneumatic or electromagnetic signal to force.

142
Q

anticipating control

A

Anticipating control is the ability to foresee potential changes and take proactive measures to artificially active this control earlier than otherwise

143
Q

averaging element

A

A thermostat that responds to the average duct temperature

144
Q

Coefficient of linear thermal expansion

A

(Thermal expansion) Change in length of a metal due to temperature change

145
Q

opposed blade damper

A

each alternating blade rotates in the opposite direction of the one besides it to throttle airflow without changing the direction of the air

146
Q

parallel blade damper

A

each alternating blade rotates in the same direction of the one besides it to throttle airflow and change the direction of the air

147
Q

direct acting

A

The output signal changes in the same direction of the controlled variable changes. E.G: an increase in resistance from an increase in temperature

148
Q

Reverse acting

A

The output signal changes in the opposite direction of the controlled variable changes. E.G: a decrease in resistance from an increase in temperature

149
Q

thermistor

A

A heat sensitive resistor, worse than RTD but can be positive or negative acting

150
Q

Transducer

A

An electronic pressure sensor utilizing piezoelectric effect to create impedance in a control loop

151
Q

What’s the difference between P, PI, and PID electric control systems

A

P - proportional no algorithm
PI - proportional integral time algorithm
PID - proportional integral derivative time and temperature algorithm

152
Q

What the difference between pump down and solenoid drop

A

solenoid drop -> everything shutdown at the same time
pump down -> waits for low pressure controller to open

153
Q

another name for allen keys

A

Hex keys are also known as Allen keys.

154
Q

another name for pump pliers

A

Another name for pump pliers is slip-joint pliers.

155
Q

bourdon tube

A

Only bourdon tubes can measure both pressure and vacuum

156
Q

How much microns of vacuum should refrigeration systems be at

A

500 or below microns

157
Q

What angle do flaring tools flare at

A

45°

158
Q

What tank size do we normally use for acetylene

A

B tank

159
Q

From what pressure does acetylene regulators reduce them to what pressure

A

250psi to 15psi

160
Q

What colour is the oxygen hose

A

Green

161
Q

What is brass composed of?

A

Copper and zinc

162
Q

What is a street coupling

A

A copper fitting with on side flared

163
Q

What can be used in compression fittings instead of flaring

A

Ferrule

164
Q

What are the 2 common black pipe sizes

A

Sched 40 and sched 80

165
Q

What temps r considered soft soldering and brazing?

A

Solf soldering: <800°F
Brazing: >800°F

166
Q

Is steel a ferrous material

A

Yes

167
Q

Is brass a ferrous material

A

No

168
Q

Cast iron is very porous and brittle?

A

TRUE

169
Q

Aluminum is a ferrous material

A

No

170
Q

What is brass composed of

A

Copper and zinc

171
Q

What is Teflon

A

A plastic polymer. Can be used for thread sealing.

172
Q

What is white, yellow, and pink Teflon tape used for?

A

Plumbing, natural gas, and refrigerant

173
Q

How do you grade bolts with the lines on the bolts

A

Lines + 2 = grade

174
Q

What are these

A

Set screws

175
Q

How many stages are recommended for torquing procedures

A

3

176
Q

At what pressure is gas regulated at at the service regulator at the house meter?

A

7” to 14”WC

177
Q

1 psi = __ “WC

A

1 psi = 28”WC

178
Q

Adsorption

A

Water vapour is removed by passing through granular solids that attract water.

179
Q

Absorption

A

Water vapour is removed by bubbling the natural gas through a liquid desiccant often a glycol solution. The desiccant absorbs the water

180
Q

How many BTUs can gas fitter Bs work on

A

Up to 400k BTUs

181
Q

input rating

A

The heat produced in BTU/hr per unit of fuel burned.

182
Q

1 gallon

A

10 lbs of water

183
Q

propane boiling point

A

-44°F

184
Q

methane boiling point

A

-258°F

185
Q

How many times does propane expand compared to its original size when changing from liquid to gas?

A

270x

186
Q

specific gravity of propane

A

1.5

187
Q

specific gravity of methane

A

0.6

188
Q

calorific value

A

The quantity of heat per unit mass obtained. BTU/gallon

189
Q

BTU per cu ft for propane

A

2500Btu/cuft

190
Q

BTU per cu ft for methane

A

1000Btu/cuft

191
Q

Ignition temperature of methane

A

1200°F

192
Q

Ignition temperature of propane

A

950°F

193
Q

Maximum flame temperature of methane

A

3350°F

194
Q

Maximum flame temperature of propane

A

3500°F

195
Q

Flame speed of methane

A

26”/s

196
Q

Flame speed of propane

A

32”/s

197
Q

Range of Flammability

A

The percentage of gas present in a gas/air mix between the upper an lower limits that will burn

198
Q

Flame speed

A

the measured rate of expansion of the flame front in a combustion reaction.

199
Q

combustion air required for methane

A

10cuft

200
Q

combustion air required for propane

A

24cuft

201
Q

Gas pressure test for finish piping

A

10min, working pressure test

202
Q

Gas pressure at finish piping

A

3-4”WC

203
Q

Propane pressure after low pressure regulator

A

11” - 14” WC

204
Q

Why does lowering the pressure lower the boiling point

A

Lowering the pressure reduces the boiling point because it decreases the force holding the liquid molecules together, making it easier for them to escape as vapor.

205
Q

atmospheric pressure in psiA and kpaA

A

atmospheric pressure: 14.7 psi and 101.3 kpaA

206
Q

absolute zero in Celsius and Fahrenheit

A

Absolute zero: -273°C and -460°F

207
Q

How much excess air do you generally need for a complete combustion?

A

40%

208
Q

Boyle’s law

A

Increase in pressure = decrease in volume
Temp is constant

209
Q

Charles’ first law

A

Increase in temp = increase in pressure
Volume is constant

210
Q

Charles second law

A

Increase in temp = increase in volume
Pressure is constant

211
Q

What are slinger rings

A

Slings condensate onto the condenser which increases heat transfer of the condenser

212
Q

What are swamp coolers

A

Also called evaporative coolers that are most often used with exhaust systems (restaurants). Feeds water to a media that sends moist water as cooling.

213
Q

What are terminal units

A

Heat exchangers that receives are from the central air handling unit.

214
Q

What are makeup airs

A

Exchanges indoor air

215
Q

Direct-fired vs indirect-fired makeup air

A

Direct-fired: exposed flame that adds heat.
Indirect-fired: has heat exchanger.
Both need running exhaust systems

216
Q

What are the 2 types of fans

A

Centrifugal (blowers, squirrel cages) and propellers

217
Q

For blowers, air enters at a _ degree to the fan

A

90 degree

218
Q

What kind of bearings don’t need lubrication

A

When they are made of an alloy with lead

219
Q

What are axial fans also called

A

propeller fans

220
Q

Are propeller fans overloading fans

A

Yes because they push instead of throw/slap air

221
Q

Propeller fans are seated to sit how far out the shroud

A

1/3 of propeller blade height

222
Q

Examples of light duty and heavy belts

A

Light duty: 4L, 5L.
Heavy duty: A, B.

223
Q

When the belt starts squeaking, it needs lubrication.

A

No

224
Q

In a mixing chamber, outdoor air makes up at minimum how much of the total air

A

10-20%

225
Q

Portable air conditioners do what to moisture in the air

A

Extract moisture

226
Q

Why do you always close the covers of fan housings

A

So they don’t overload

227
Q

What type of backward inclined fan blade is the most efficient

A

Curved airfoil

228
Q

Which type of fan blade is good for moving dirty air

A

Radial fan

229
Q

What color is r717 cylinder

A

Silver

230
Q

How much ppm differentiates low and high toxicity refrigerants

A

400ppm

231
Q

What weight must refrigerant cylinders not exceed

A

300lbs

232
Q

Blended refrigerants are numbered what

A

Zeotropic: 400s
Azeotropic: 500s

233
Q

Zeotropic refrigerants experiences what

A

Temperature glide when saturated

234
Q

Do azeotropic refrigerants experience glide?

A

Yes, but it’s negligible

235
Q

Zeotropic vs azeotropic

A

Zeotropic is a mixture and can be distilled whereas azeotropic cannot

236
Q

What’s good practice when charging and evacuating refrigerant

A

Charge and evacuate as a liquid

237
Q

Montreal Protocol when

A

1987

238
Q

Hygroscopic

A

Attracts/retains moisture

239
Q

Floc point

A

Temperature which waxy stuff comes from the oil

240
Q

How much refrigerant do you need for push pull recovery

A

20lbs

241
Q

You must report refrigerant leaks over

A

10kg or 22lbs

242
Q

What can you use for ammonia leaks

A

Litmus paper or sulphur sticks

243
Q

What should you do to vacuum pumps before every use

A

Replace oil

244
Q

What’s the triple evacuation process

A

Vacuum -> inert gas (nitrogen) x3

245
Q

POE oil max exposure time to atmosphere

A

5min

246
Q

TDG

A

Transportation of Dangerous Goods Act

247
Q

What’s an easy indication of a leak of refrigerant in refrigerant system

A

Oil

248
Q

What are hydronics

A

Use of water for heating and cooling

249
Q

What’s an application specific controller

A

Controls 1 type of equipment

250
Q

What are the three most common networking protocols

A

Lontalk, BACnet, Modbus

251
Q

Pneumatic receivers store pressures between what PSIs and has a pressure relief at what PSI

A

Stored at 60 - 90psi, and reliefs it at 120psi

252
Q

Air dryers cool the air to what temperature

A

34°F

253
Q

Are zone valves NC or NO for cooling valves

A

NC. But NO for heating valves

254
Q

Prefered RH

A

30% - 60%

255
Q

What are VOCs

A

Volatile organic compounds: toxic carbon based substances. Stuff like bleach and drain cleaners

Hvac (14 decks)

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