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2nd Year SM > Res Furn Test 1 > Flashcards

Res Furn Test 1 Flashcards

1
Q

What is the purpose of a thermocouple?

A

To produce 20 to 30 millivolts of power to energize an electromagnet in the power unit which keeps gas flowing to the pilot.

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2
Q

The power unit and the thermocouple together make up a system called:

A

Flame safeguard.

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3
Q

Three bimetal temperature sensing devices are:

A

Stripe type, spiral type, and disc type.

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4
Q

What is the purpose of an anticipator?

A

Anticipate the temperature in the room, shutting down the furnace just before the temperature reaches the setting on the thermostat.

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5
Q

On a heat only thermostat, the contacts will:

A

Close on temperature decrease.

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6
Q

The fan control in the furnace:

A

Turns the fan off between 90F and 100F and on between 120F and 140F.

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7
Q

True or false: Limits with reset on them can be used to replace snap disc fan controls with summer fan switches?

A

False.

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8
Q

What is the main purpose of a limit switch?

A

To shut down the gas supply, should the furnace get too hot.

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9
Q

Transformers found in furnaces:

A

Take 120 volts AC and transform it into 24 volts AC through magnetic induction.

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10
Q

The rating plate on a furnace has information about:

A

The output of the furnace.

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11
Q

The diagram that would show you the most information about sequence of operation is an:

A

Flow chart

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12
Q

The designation L1 (Hot) on a ladder diagram means:

A

Hot or black wire

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13
Q

True or false: The switch is always placed before the load on a ladder diagram?

A

True

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14
Q

All electrical circuits require which three things?

A

Load, conductor, and power source

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15
Q

How are the controls on a wiring diagram shown?

A

Appliance off

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16
Q

Name the three main designs of pilot burners.

A

Non-aerated
Aerated
Post-aerated(incinerating/target)

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17
Q

What is the primary function of a pilot?

A

To effectively ignite the main burner

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18
Q

What is the secondary function of some pilots?

A

Activating a flame failure device (via thermocouple)

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19
Q

What is another term used to describe an Aerated pilot?

A

Bunsen or linting.

20
Q

A post-aerated pilot utilizes primary air and secondary air, but has no _____.

A

A post aerated pilot utilizes primary air and secondary air but has no MIXING TUBE.

21
Q

Define: Proved Pilot

A

A pilot flame that is supervised by a flame failure device (thermocouple).

22
Q

Define: Standing Pilot

A

A pilot that burns constantly whether the main burner is fired or not.

23
Q

Define: Expanding Pilot

A

A pilot that constantly burns at a low turndown but is automatically increased at the call for heat for proper ignition.

24
Q

Define: Intermittent Pilot

A

A pilot that is automatically ignited at the call for heat, ignites the main burner and remains on throughout the main burner cycle.

25
Q

Define: Interrupted Pilot

A

A pilot that is automatically ignited at the call for heat, ignites the main burner and is extinguished once the main burner is proven lit.

26
Q

List the purpose of having different flame patterns for a gas pilot.

A

Ignite the main burner under all conditions while providing heat to the thermocouple. The heat from the main burner flame shall not come in direct contact with the thermocouple.

27
Q

What is the fixed element that controls the amount of gas that a pilot will burn?

A

The orifice.

28
Q

Name the adjustable component that controls the amount of gas the pilot will burn.

A

A needle valve or, on larger appliances, a pilot regulator.

29
Q

What is the most common problem associated with a pilot that produces an orange flame?

A

Dirt, dust, and other impurities in the air used for combustion.

30
Q

The two types of hook-ups used for safety devices are ____ hookup and ____ hookup.

A

The two types of hook-ups used for safety devices are SAFE hookup and 100% SAFE hookup.

31
Q

What is the electromagnetic device used as a load in a safety circuit usually called?

A

Power unit.

32
Q

What is the recommended distance from the ends for bending a thermocouple?

A

The rule is ONE INCH. In extreme cases, it can be bent 1/2” from the ends, but caution must be exercised.

33
Q

What is the recommended output range for the open-circuit test on a thermocouple?

A

17 to 32 millivolts (mV).

34
Q

What is the recommended output range for the closed-circuit test on a thermocouple?

A

8 - 17 mV.

35
Q

What is required by a thermocouple open-circuit reading that exceeds 32 mV?

A

The pilot flame must be reduced to achieve 32 mV maximum.

36
Q

What is the solution for a failed turn-down test?

A

Relocate the pilot burner.

37
Q

Name the type of electrical current generated by a thermoelectric device?

A

Direct current (DC).

38
Q

What does the electrical output of a thermoelectric device depend on?

A

The amount of heat applied to the thermocouple and the difference in temperature between the hot and cold junction.

39
Q

What does an analysis of a thermocouple reading 30 mV open and 15 mV closed indicate?

A

Acceptable.

40
Q

What does an analysis of a thermocouple reading 26 mV open and 6 mV closed indicate?

A

Replace thermocouple.

41
Q

What does an analysis of a thermocouple reading 16mV open and 16mV closed indicate?

A

Check power unit (also, a weak thermocouple; replace at the same time)

42
Q

The pilot flame should cover the tip of the thermocouple by ____.

A

The pilot flame should cover the tip of the thermocouple by 3/8” INCH to 1/2” INCH.

43
Q

Name two functions of a thermopile can perform.

A

Operate the safety system (power unit)

Operate the main burner gas valve (operating gas valve)

44
Q

A thermopile is a number of thermocouples connected in ____.

A

in SERIES.

45
Q

If the wiring on a thermopile circuit exceeds 80 feet, a ____ system should be considered.

A

a 24-VOLT system

46
Q

What is the thermopile test called that is similar to the drop-out test performed on thermocouples?

A

Pull-in voltage test.

47
Q

What test is used on thermopile system to test proper ignition of the main burners at a low pilot flame condition?

A

An effective ignition test.

2nd Year SM (8 decks)

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