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Austin's Sheet Metal 4th Year > Troubleshooting > Flashcards

Troubleshooting Flashcards

1
Q

Household electrical outlets contain what kind of current?

A

AC

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2
Q

A 24 voltage hot surface intermittent pilot ignition system is know as a?

A

Smart valve

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3
Q

An interrupted pilot ignition system, what state are the main burner and pilot during standby?

A

They are both off

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4
Q

In which ignition system does the pilot stay on once the main burner is lit?

A

Intermittent

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5
Q

In a direct ignition system, what lights the burner in place of the pilot?

A

A spark

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6
Q

In a pilot ignition system, with an HSI, what lights the pilot and what lights the main burner

A

The HSI lights the pilot and the pilot lights the main burner

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7
Q

Name the 2 parts of a dual rod pilot burner

A

The short rod is the spark igniter and the second rod is the flame sensor

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8
Q

Where is a flame rod mounted

A

So it will be immersed in the main burner flame

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9
Q

What 2 voltages do HSI’s normally come in

A

80V or 110V

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10
Q

What’s the advantage of a valve train

A

It’s allows you to replace components as needed instead of replacing the entire gas valve if there is a failure

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11
Q

What happens to the voltage during flame rectification

A

It changes from AC to DC

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12
Q

What is the ratio of the burner ground to the flame rod in flame rectification

A

1:4 This is to ensure the current can be rectified from AC to DC

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13
Q

Can a continued trial for ignition be allowed on propane appliances or direct ignition systems

A

No

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14
Q

How many times does the polarity change direction in a 60hz system

A

120 times a second

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15
Q

What type of wring diagram shows the color of wires, the components, and how they are connected to an appliance in standby mode?

A

Pictorial or connection diagram

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16
Q

What does a schematic or ladder diagram show?

A

How the appliance works for troubleshooting purposes

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17
Q

What 3 components make up a combination gas valve

A

The solenoid valve, diaphragm valve and the pressure regulator

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18
Q

What is the name given to the sequence of operations that take place before the gas valve opens?

A

Pre purge

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19
Q

What is the first step of sequence of operation for a heating appliance with electronic ignition

A

Call for heat at the thermostat

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20
Q

What are the typical voltage input and output of a transformer

A

120V input
24V output

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21
Q

What is used to measure gas pressure

A

Manometer

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22
Q

When using a multimeter to check for continuity, is the appliance on or off

A

It is off. The meter provides the power for the test

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23
Q

A multimeter will read volts in what type of circuit? And amps in what circuit?

A

Voltage in parallel and amperage in series

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24
Q

1 psi = how many inches of water colum

A

27.7” wc

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25
Q

What is used to measure the flow of electrons

A

Amperage

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26
Q

If you are using voltage, what are you measuring in regards to the electrons

A

The force being applied to them

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27
Q

What is the formula to calculate watts

A

Volts x Amps = Watts

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28
Q

How does a transformer create energy

A

Depending on the number of Wraps, 120 Wraps on the 120V side and 24 Wraps on the 24V side. The energy is created in a electromagnetic field

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29
Q

What safety control switch opens on temperature rise

A

High limit switch

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30
Q

What does the thermostat “Switch” do on temperature drop

A

It closes on temperature fall

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31
Q

What part of the furnace takes heat from the products of combustion and moves it to a space that requires heat?

A

Heat exchanger

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32
Q

What is the sequence of operations for a standard efficient furnace

A
  1. Call for heat
  2. Gas valve opens
  3. Main burner lights
  4. Blower turns on
  5. Heat is satisfied
  6. Gas valve closes
  7. Fan control is satisfied
  8. Blower turns off
  9. Furnace is back in standby
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33
Q

What are the following thermostat terminals

RH
RC
W
Y
G
C

A

RH - 24V power for heating
RC- 24V power for cooling
W - heat Relay or valve
Y - Cooling
C - Common
G Blower fan Relay

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34
Q

What is the recommended manifold pressure for a natural gas furnace

A

3.5” wc

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35
Q

What gauge of wire is used for 120V side and the 24V side of the furnace?

A

120V side uses 14 gauge
24V side uses 18 gauge

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36
Q

What 2 factors should be checked when calibrating thermostats

A

Operating temperature, and operating differential

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37
Q

What control piece of equipment can be used to reset a lock out on a furnace

A

Thermostat

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38
Q

Name a component that is an automatic or a remote control device that uses one or more initiating devices to operate or control another device

A

A Relay

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39
Q

What component is used to either increase the running efficiency of the motor or give it an initial boost in torque at start-up

A

Capacitor

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40
Q

What is the recommended way to discharge a capacitor

A

A high wattage resistor

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41
Q

Is the flame roll out switch on a furnace automatic or manual reset

A

Manual

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42
Q

What is the purpose of the inducer motor

A

To assist the flue gases to rise up through the vent

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43
Q

How is a pressure switch connected and wired

A

It is connected to the inducer motor assembly and wired in series with the gas valve

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44
Q

What does a manometer measure

A

Pressure

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45
Q

What type of pressure is found on the supply side and what type of pressure is found on the return side of a system

A

Supply is positive and return is negative

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46
Q

What type of meter combines a voltmeter, ohm meter and amp meter

A

Multimeter

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47
Q

Name four types of efficiencies

A

Combustion efficiency
Steady state efficiency
Annual fuel utilization efficiency
Thermal efficiency

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48
Q

What is the stack temperature or flu exhaust temperature of a standard efficient furnace? A mid efficient? A high efficient?

A

Standard - 500°F
Mid - 350°F
High - 110°F

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49
Q

What does low oxygen indicate when troubleshooting a furnace in regards to combustion

A

There is insufficient combustion air

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50
Q

What does high oxygen levels indicate when troubleshooting a furnace in regards to combustion

A

Too much combustion air

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51
Q

Which dial is used for the purpose of clocking the meter

A

The proving dial

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52
Q

What can be done if the temperature rise on a furnace start up is to low or to high?

A

If it is to low you must decrease the fan speed and if it is to high you must increase the fan speed

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53
Q

What are two ways to adjust the fan on and the fan of setting on a furnace

A

Switching positions of dip switches or changing locations of a jumper

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54
Q

What is the sequence of operations for a high efficient furnace

A

Call for heat R-W closes- 24V
The inducer motor starts- 120V
The pressure switch closes- 24V
The HSI energizes- 120V
Main valve energizes- 24V
Ignition takes place- flame proves 0.8secs
HSI de-energizes
Main blower energizes- 120V
Call for heat is satisfied R-W opens
Main valve de-energizes
Inducer motor runs a post purge and then shuts down - 5 second delay
Blower fan turns off 90-210 second delay
Furnace is now in standby

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55
Q

When using electronic ignition, what’s the process of proving the flame called

A

Flame rectification

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56
Q

What is the importance of a ladder diagram

A

It shows how appliances work for troubleshooting

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57
Q

What is the difference between interrupted and intermittent pilot

A

Intermittent pilot continues to burn with main burner. Cheaper, less parts.

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58
Q

Hot surface ignition systems are usually what time of ignition

A

Direct ignition

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59
Q

What are the parts of a dual rod pilot

A
  1. Spark igniter
  2. Flame sensor
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60
Q

What is a HSI made of

A

Silicon Carbide

Newer HSIs are made of Silicon Nitrate (last twice as long)

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61
Q

How does a direct-spark ignition system work

A

The system turns on the main burner gas, lights the burner, and proves the flame

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62
Q

Do direct fire ignition modules have a fuse

A

Older modules do, but newer ones do not. Appliance manufacturer is left to supply a fuse protection in the wiring of the application

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63
Q

What happens if the spark from the ignition touches the main burner

A

It will eventually blow a hole in the burner casting, spark should NEVER touch main burner

64
Q

How do you handle a HSI with your BARE hands/fingers

A

ONLY on the ceramic base. Getting oil from your skin on the hsi can cause uneven heating and wear and tear on the HSI

65
Q

What do you use to clean a flame rod

A

Only scotch Brite pads or 000 steel wool

66
Q

With HSi igniters, what are the steps to flame ignition

A
  1. HSI is allowed to heat up pass the temperature required to light the gas
  2. Main gas valve is energized
  3. Ignition of the burner takes place
67
Q

What are the 2 main principles of rod defection systems

A
  1. Flame rectification
  2. Flame conductivity
68
Q

What is the definition of a Rectifier

A

A device used for converting alternating current into direct current

69
Q

Will the flame conduct electricity

A

Yes, ionized particles that form from the burning gas conduct electricity

70
Q

Define Flame Ionization

A

Heat from the flame causes the molecules between the electrodes to collide with each other, this removes electrons knocked off molecules and ions are formed

71
Q

What is the start up sequence of operations from “call for heat” to energize a ignition module

A
  1. Call for heat
  2. R-W terminals close
  3. Energizes inducer fan Relay
  4. Starts inducer fan
  5. Pressure switch closes (air pressure increase in response to fan)
  6. Allows power to flow to ignition module
72
Q

List 5 parts of a Relay

A
  1. Coil
  2. Core
  3. Return spring
  4. Armature
  5. Contacts
73
Q

What are the 4 most common arrangements for the contacts on a Relay

A
  1. SPST - NO (Normally open) single pull single throw
  2. SPST - NC (Normally closed)
  3. DPDT - Double pole double throw
  4. SPDT - Single pole double throw
74
Q

Name the 2 most common capacitors used in HVAC systems

A
  1. Run capacitor
  2. Start capacitor
75
Q

What is the material called that is used to super heat the two plates in a capacitor

A

Dielectric

76
Q

What activates the pressure switch

A

The pressure switch is activated when the IDM (induce motor) starts turning and creates enough pressure, it will force the diaphragm to move towards the microswitch, closing it

77
Q

What is flame rectification

A

Flame rectification is an AC electrical circuit that sends a very small current from the furnace electronic board-up to the flame rod. When the flame is established, the flame acts as a path or a conductor. Which allows the current to flow across the flame from the rod to the ground (burner), thus completing the circuit

78
Q

Where is the CPU located

A

The electronic control board contains the CPU in most modern HVAC equipment

79
Q

Define Relay

A

A Relay is a device or a remote control device that uses one or more initiating devices, such a switch, to operate or control another device connected either in the same circuit or in another circuit.

They can be operated electro-mechanically or electronic solid state components

80
Q

On a schematic wiring diagram, what state are relays drawn in

A

It is always shown in the de-energized state and the contacts are said to be in their normal position. That is the position they are in when the coil is NOT energized

81
Q

Regarding relays, what applications are SPST and DPDT Used for?

A

For switching equipment off and on

82
Q

Define TDOE Relay
(Time Delay On Energization Relay)

A

When contacts change only after a specified time has passed from the moment the relay is energized

83
Q

Define (TDOD) Relay
Time Delay On De-Energization Relay

A

When the contacts change instantly when the relay is energized, BUT will revert back to their original position only after a specified time when the relay is de-energized

84
Q

Define Capacitance

A

Capacitance is the ability of a electrical device to store energy into a electrostatic field and release energy from the electrostatic field to a electrical circuit

ALSO

Is the ability of an electrical device to oppose any change in voltage across any change in voltage across that said device

85
Q

What is the international system of units (SI) for capacitance

A

Farad

86
Q

Define SI Unit, Coulomb

A

The coulomb (symbol: C) is the unit of electric charge in the International System of Units (SI).It is equal to the electric charge delivered by a 1 ampere current in 1 second and is defined in terms of the elementary charge

87
Q

Name 3 types of dielectric materials

A
  1. Air dielectric (least capacity)
  2. Paper dielectric (more capacity)
  3. Ceramic dielectric (greater capacity)
88
Q

What must be done before testing a capacitor

A

You MUST discharge the stored energy

89
Q

What are the 2 methods you can use to de-energize a capacitor

A
  1. Place leads of a high voltage RESISTOR On the leads of the CAPACITOR
  2. PLace leads on 100 watt electric BULB on the leads of the CAPACITOR
90
Q

What types of furnaces have inducer motors

A

All furnaces that are

  1. Mid-Efficient
  2. High-Efficient
91
Q

What does a pressure switch prove in a furnace operation

A
  1. That the inducer motor is running (IDM)
  2. NO obstructions in the venting system
92
Q

What does a pressure switch consist of

A
  1. Diaphragm
  2. Microswitch
93
Q

Purpose of the inducer motor

A
  1. Draw the correct volume of air for the heat exchanger
  2. Assist the flue gasses in rising up through the venting
94
Q

Purpose of the flame roll out switch

A

To detect any flame that blows back or rolls out of the combustion chamber

95
Q

How many flame roll out switches are in furnaces

A

Two of them. One on each side of the burner box

96
Q

How does a flame roll out switch reset after it opens

A

It must be manually reset at the switch, there is a little red button between contacts on the switch

97
Q

Regarding high limit switches, is the switch normally open or close?

A

Normally closed, when exposed to high temperature the switch opens

98
Q

Can the set points of a high limit switch be changed by a HVAC journeyman?

A

No, they are factory calibrated and cannot be adjusted or tampered with.

99
Q

How hot do HSI’s get?

A

Raise to approximately 2600°F (1427°C)

100
Q

What does CPU stand for

A

Central processing unit

101
Q

What is the function of the CPU

A

CPU contains a number of electronic circuits that can execute a sequence of stored instructions called computer programs

102
Q

What are the 4 steps that a CPU uses in its operation

A
  1. Fetching
  2. Decoding
  3. Executing
  4. Write back
103
Q

Where are CPUs found on furnaces

A

On the control board normally

104
Q

Where are high pressure switches (HPS) found in a heating/cooling system

A

Located in the tubing between the discharge side of the compressor and the condensing coil in a furnace

105
Q

What is the purpose of a low pressure switch (LPS) in refrigeration

A

Monitors the refrigeration system for a loss of charge

Also helps preventing the indoor coil from freezing up, due to dirty filter or low air Airflow over the indoor coil

106
Q

What is the main difference between an intermittent pilot gas valve and a direct ignition gas valve

A

The direct ignition gas valve has no pilot connection

107
Q

What is the recommended flame rod to ground connection ratio

A

1:4
1(Flame) - 4(Ground rod)

An AC voltage on the flame rod will conduct current through the flame to a grounding surface, usually the metal parts of the burner. The signal will be rectified to DC with a 1 to 4 ratio of surface areas of the burner ground and flame rod that are in contact with the flame.

108
Q

What is the first step in sequence of operation for any heating appliance with electronic ignition

A

Call for heat from the thermostat

109
Q

What is the importance of connection diagrams

A

It shows where the wires go and the colors of each wire

110
Q

In a furnace, what component is connected to a capacitor

A

Blower Motor (BLM)

111
Q

Define interrupted pilot ignition system

A

a pilot that is automatically ignited when an appliance is called on to operate and is automatically extinguished after the main burner operation has been initiated.

112
Q

Concerning refrigeration, how are High Pressure Switch and Low Pressure Switch (HPS & LPS) reset once tripped

A

Manually, either in the unit or by turning off the thermostat

113
Q

It is considered safe practice to inspect components with the power on True or False

A

False

114
Q

A typical furnace circuit board will only have one voltage

True or False

A

False, it normally have 120V on the primary side of the transformer and 24V on the secondary side of the transformer

115
Q

What should be checked on the furnace blower assembly when starting up a furnace for the first time

A

Confirm that all shipping blocks and bolts have been removed. Also the wheel should be checked to make sure it’s running on the center of the housing and not off crooked.

116
Q

List 3 methods to test for a gas leak

A
  1. Test dial
  2. Commercial leak detector
  3. Electronic leak detector
117
Q

What direction must the Venting on a furnace slope and what grade should it have

A

Venting must be moving upward and away from the furnace to the outside of the building envelope. Venting must be graded 1/4” per foot back to the furnace for proper grade.

118
Q

What is the max support that supports can be apart on Venting PVC 636

A

5 feet MAX

119
Q

What should you be looking for when checking duct connections

A

Openings or gaps that may cause excessive leakage

120
Q

What should the heat anticipator setting match

A

The amperage draw of the 24 Volt circuit

121
Q

What are the reasons for getting the manifold pressure

A

Setting the manifold pressure is a critical adjustment that is made not only to ensure that the appliance is not over firing, but can be used to derate the appliance as well.

Setting the gas pressure extends the life span of components in the furnace

122
Q

What are the formulas for converting gas quantity into BTUh

A
  1. Hourly consumption = size of test dial x 3600 seconds for one full revolution of test dial
  2. BTUh = Hr consumption x Calorific value of the gas
123
Q

What are the Calorific values of Propane and natural gas

A

Natural Gas - 1000/ft²
Propane - 2500/ft²

124
Q

How is temperature rise calculated

A

The difference between the return air and supply air temperature

125
Q

When do the blower speeds have to be changed on a furnace

A

The blower speed must be changed if the temperature rise is to high or to low

126
Q

What 3 items does a combustion analyzer test when testing efficiency

A
  1. CO2
  2. O2
  3. Excess air
127
Q

What is a draft gauge used for

A

To measure flue draft and pressure drop across air filters

128
Q

List 3 types of efficiencies

A
  1. Combustion
  2. Steady state thermal
  3. Annual fuel utilization
129
Q

Define annual fuel utilization efficiency

A

It measures the amount of heat actually delivered to the enclosure, compared to the amount of fuel you must supply to the appliance in a season

It also takes into account the cycle losses and associated energy losses of the heating unit as it responds to change in the load, which in turn, is affected by changes in weather and operator controls

130
Q

What dial is used in the purpose of clocking the meter

A

Proving dial

131
Q

What is the formula for calculating BTUh after clocking the meter

A

Btuh = (volume test dial X 3600/ time 1 revolution) calorific value

132
Q

What is the Calorific value of Natural Gas

A

1000 BTU

133
Q

List conditions that could possibly cause low O2 in the flue gas

A
  1. Insufficient combustion air
  2. Burner over firing
  3. Low vent (stack) draft
134
Q

List 3 conditions that may cause low vent draft in an appliance

A
  1. Improperly sized vent
  2. Vent system blocked
  3. Poor workmanship
135
Q

ThE LED light on a printed control board (PCB) can be used to help aid in the fault of a furnace

True or False

A

True

136
Q

Every manufacturer uses LED fault on their control boards

True or False

A

True

137
Q

You should turn the power off to the appliance before you read the LED fault code

True or False

A

False

There must be power to the appliance to flash the code for you

138
Q

List the 4 possible causes for a pressure switch not closing

A
  1. Blocked vent pipe
  2. Damaged tubing from the inducer draft assembly to the pressure switch
  3. Faulty inducer motor
  4. Dirty or worn inducer fan wheel
139
Q

List 5 possible causes for a limit switch to open

A
  1. Plugged filter
  2. Restriction in the duct work
  3. Loose blower
  4. Faulty blower motor
  5. Faulty switch or electrical connection
140
Q

Where is the flame roll out switch located

A

Beside the burners

141
Q

A flame sensor is checked by measuring the amount of what flowing through it

A

DC microamps

142
Q

All HSI’s are supplied with 110 Volts

True or False

A

False

Some HSI’s are 240 Volt

143
Q

Can a over sized furnace shorten the lifespan of a HSI?

A

Yes, excessive temperature will wear out the HSI

144
Q

The troubleshooting procedure
for a direct drive multi-speed
motor is exactly the same as it is
electronically commuted motor

TRUE or FALSE

A

False

145
Q

Air velometer can measure airflow
in cfm directly from any diffuser
grill or register

TRUE or FALSE

A

FALSE

Holes are drilled into duct to insert probe.

146
Q

What is the maximum static pressure of a velometer?

A

10” wc

147
Q

When performing a rectangular
duct traverse, the duct cross-section must be divided into a number of equal sections and the reading should be taken at the _____ of each of the sections

  1. Right
  2. Left
  3. Centre
  4. Bottom
A
  1. Centre
148
Q

What is the minimum number of
readings that should be taken when performing a rectangular duct traverse?

A

12 readings is the minimum

149
Q

What is the formula for corverting fpm to cfm on retangular duct?

A

The average fpm readings multiplied by the square footage of the duct.

150
Q

A round duct traverse is performed using the same method as the rectangular duct traverse

TRUE or FALSE

A

False

151
Q

AK factor are the same for all type of diffusers, grills or registers

TRUE or FALSE

A

False

152
Q

When balancing a HVAC system, you must start with all the dampers in what position?

A

All dampers must be in fully open position

153
Q

What is the correct formula for calculating percent of design?

A

Preliminary cfm divided by Design cfm

154
Q

The first outlet to be adjusted is
the outlet with the what percent of
design pressure?

A

The second lowest percentage of design

155
Q

To convert fpm to cfm at a diffuser grill or register, you would use the formula?

A

CFM = AK x FPM

156
Q

Why has flame conductivity systems not been used for proving the flame ?

A

The system will not distinguish between a flame and a shortage

Austin's Sheet Metal 4th Year (9 decks)

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