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HVAC Troubleshooting > Testing and Troubleshooting > Flashcards

Testing and Troubleshooting Flashcards

1
Q

What three items does a combustion analyser sample when testing efficiency?

A

CO2, O2, and Excess air

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2
Q

What is a draft gauge used for?

A

To measure flue draft and pressure drop across air filters

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3
Q

What are four types of efficiencies?

A

Combustion, steady state, thermal, and annual fuel utilization

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4
Q

Which dial is used for the purpose of clocking the meter

A

The proving dial

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5
Q

What is the calorific value of natural gas?

A

1000 BTU

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6
Q

What is the calorific value of propane gas?

A

2500 BTU

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7
Q

What are the conditions that could possibly cause low O2 in the flue gas?

A

Insufficient combustion air, burner over firing, and low vent (stack) draft

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8
Q

What are 3 conditions that may cause low vent draft in an appliance?

A

Improperly sized vent, vent system blocked, and poor workmanship

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9
Q

On the PCB, What can be used to aid in the diagnosis of a fault in a furnace?

A

The LED

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10
Q

Every manufacturer uses LED fault codes on their circuit boards. True or False?

A

True

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11
Q

Should the power be turned on or off before you read the fault codes?

A

Turned on

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12
Q

What are the possible causes for a pressure switch not closing?

A

Blocked vent pipe, faulty tubing, faulty induced draft motor, and dirty or worn induced fan wheel

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13
Q

What are the possible causes for a limit switch to open?

A

Plugged filter, restriction in the duct work, loose blower wheel, faulty blower motor, and faulty switch or electrical connections.

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14
Q

Where is the rollout switch located?

A

Beside the burner

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15
Q

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

A

DC microamps

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16
Q

All HSI are supplied with 110 V. True or False?

A

False

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17
Q

What can happen to an HSI if the furnace is oversized?

A

It can shorten the life of the HSI

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18
Q

The troubleshooting procedure for a direct drive multi-speed motor is exactly the same as it is far an electronically commuted motor. True or False?

A

False

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19
Q

What are the variety of test instruments used for testing a furnace?

A

A gas analyzer, manometer, tachometer, multimeter, and thermometer

20
Q

What is the air to gas ratio?

A

10/1

21
Q

What device is used to measure gas pressure and pressure drops in ductwork?

A

A manometer

22
Q

What device is used for measuring the speed of motors and fans in HVAC equipment?

A

A Tachometer

23
Q

What device combines a voltmeter, ohmmeter, and an amp meter in one to perform service and electrical readings?

A

A multimeter

24
Q

What device is used for taking temperature readings?

A

A Thermometer

25
Q

What gauge is used for determining draft pressure?

A

A draft gauge

26
Q

What is Annual Fuel Utilization Efficiency (AFUE) ?

A

A thermal efficiency measure of combustion equipment like furnaces, boilers, and water heaters.

27
Q

What is combustion efficiency?

A

It is a calculated measurement in percent of how well the appliance converts the fuel into useable heat at a specific point in time.

28
Q

What is steady-state efficiency?

A

It used to describe combustion efficiency

29
Q

What is running efficiency?

A

It is defined as the point at which combustion gas content reaches equilibrium and stack temperatures stabilize.

30
Q

What is annual fuel utilization efficiency (AFUE)?

A

It is the off cycle losses of equipment

31
Q

What is the stack temperature and running efficiency in a standard low-efficient furnace?

A

Stack temperature 500 degrees F and a running efficiency of 70 - 79 percent

32
Q

What is the stack temperature and running efficiency in a mid-efficient furnace?

A

Stack temperature 350 degrees and a running efficiency of 80 - 83 percent

33
Q

What is the stack temperature and running efficiency in a high-efficient furnace?

A

Stack temperature 110 degrees F and a running efficiency of 90 - 98 percent

34
Q

What is the smallest dial on the gas meter?

A

The test dial

35
Q

What is the formula for flow rate?

A

Vol of dial X 3600 / time

36
Q

With less gas would you have a larger or smaller orfice?

A

A smaller orfice

37
Q

How do you convert the amount of gas used into Btuh?

A

You must multiply the cubic feet of gas consumed by its calorific value.

38
Q

What is the difference between low oxygen and high oxygen O2 and High CO levels?

A

Low oxygen has insufficient combustion gas, burner is over firing. and has a low vent draft. High oxygen combustion has too much combustion air, burner is underfiring, and has loose access panels.

39
Q

How do you diagnose a pressure switch?

A

By checking both the electrical and the diaphragm that is in the switch.

40
Q

What is a limit switch?

A

A simple auto resetting, on-off switch that opens due to excessive heat in the heat cabinet.

41
Q

What is a rollout switch?

A

It is a manual reset switch that is normally closed that opens when the temperature at the burners gets too high.

42
Q

A flame sensor has power going to it all the time. True or False?

A

True

43
Q

What are some causes of excessive on/off cycling?

A

Installation of an over-sized furnace, dirty filter or squirrel cage blower, or a dirty evaporator coil or heat exchanger.

44
Q

What are the two types of gas valves?

A

Solenoid and diaphragm

45
Q

What are the two basic types of indoor blower motors?

A

Direct drive and belt drive

46
Q

What is an electronically commuted motor (ECM)?

A

It is an ultra-high efficiency programmable brushless DC motor that uses a permanent magnetic rotor and built-in inverter.

HVAC Troubleshooting (6 decks)

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