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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

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

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13
Q

Can a cintinue 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

34
Q

What is the recommended manifold pressure for a natural gas furnace

A

3.5” wc

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

36
Q

What 2 factors should be checked when calibrating thermostats

A

Operating temperature, and operating differential

37
Q

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

A

Thermostat

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

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

40
Q

What is the recommended way to discharge a capacitor

A

A 10 watt resistor

41
Q

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

A

Manual

42
Q

What is the purpose of the inducer motor

A

To assist the flue gases to rise up through the vent

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

44
Q

What does a manometer measure

A

Pressure

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

46
Q

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

A

Multimeter

47
Q

Name four types of efficiencies

A

Combustion efficiency
Steady state efficiency
Annual fuel utilization efficiency
Thermal efficiency

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

49
Q

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

A

There is insufficient combustion air

50
Q

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

A

Too much combustion air

51
Q

Which dial is used for the purpose of clocking the meter

A

The proving dial

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

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

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

55
Q

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

A

Flame rectification

56
Q

Why have flame conductivity systems been used for proving the flame?

A

The system will NOT distinguish between a flame short and a ground short

57
Q

What is the importance of a ladder diagram

A

It shows how appliances work for troubleshooting

58
Q

What is the difference between interrupted and intermittent pilot

A

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

59
Q

Hot surface ignition systems are usually what time of ignition

A

Direct ignition

60
Q

What are the parts of a dual rod pilot

A
  1. Spark igniter
  2. Flame sensor
61
Q

What is a HSI made of

A

Silicon Carbide

62
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

63
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

64
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

65
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

66
Q

What do you use to clean a flame rod

A

Only scotch Brite pads or 000 steel wool

67
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
68
Q

What are the 2 main principles of rod defection systems

A
  1. Flame rectification
  2. Flame conductivity
69
Q

What is the definition of a Rectifier

A

A device used for converting alternating current into direct current

70
Q

Will the flame conduct electricity

A

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

71
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

72
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
73
Q

List 5 parts of a Relay

A
  1. Coil
  2. Core
  3. Return spring
  4. Armature
  5. Contacts
74
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
75
Q

Name the 2 most common capacitors used in HVAC systems

A
  1. Run capacitor
  2. Start capacitor
76
Q

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

A

Dielectric

77
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

78
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

79
Q

Where is the CPU located

A

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

80
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

81
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

82
Q

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

A

For switching equipment off and on

Sheet Metal 4th Year (7 decks)

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