Res Furn Test 1

Question 1

What is the purpose of a thermocouple?

Answer 1

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

Question 2

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

Answer 2

Flame safeguard.

Question 3

Three bimetal temperature sensing devices are:

Answer 3

Stripe type, spiral type, and disc type.

Question 4

What is the purpose of an anticipator?

Answer 4

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

Question 5

On a heat only thermostat, the contacts will:

Answer 5

Close on temperature decrease.

Question 6

The fan control in the furnace:

Answer 6

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

Question 7

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

Answer 7

False.

Question 8

What is the main purpose of a limit switch?

Answer 8

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

Question 9

Transformers found in furnaces:

Answer 9

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

Question 10

The rating plate on a furnace has information about:

Answer 10

The output of the furnace.

Question 11

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

Answer 11

Flow chart

Question 12

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

Answer 12

Hot or black wire

Question 13

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

Answer 13

True

Question 14

All electrical circuits require which three things?

Answer 14

Load, conductor, and power source

Question 15

How are the controls on a wiring diagram shown?

Answer 15

Appliance off

Question 16

Name the three main designs of pilot burners.

Answer 16

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

Question 17

What is the primary function of a pilot?

Answer 17

To effectively ignite the main burner

Question 18

What is the secondary function of some pilots?

Answer 18

Activating a flame failure device (via thermocouple)

Question 19

What is another term used to describe an Aerated pilot?

Answer 19

Bunsen or linting.

Question 20

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

Answer 20

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

Question 21

Define: Proved Pilot

Answer 21

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

Question 22

Define: Standing Pilot

Answer 22

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

Question 23

Define: Expanding Pilot

Answer 23

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

Question 24

Define: Intermittent Pilot

Answer 24

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

Question 25

Define: Interrupted Pilot

Answer 25

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.

Question 26

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

Answer 26

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.

Question 27

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

Answer 27

The orifice.

Question 28

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

Answer 28

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

Question 29

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

Answer 29

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

Question 30

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

Answer 30

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

Question 31

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

Answer 31

Power unit.

Question 32

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

Answer 32

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

Question 33

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

Answer 33

17 to 32 millivolts (mV).

Question 34

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

Answer 34

8 - 17 mV.

Question 35

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

Answer 35

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

Question 36

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

Answer 36

Relocate the pilot burner.

Question 37

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

Answer 37

Direct current (DC).

Question 38

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

Answer 38

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

Question 39

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

Answer 39

Acceptable.

Question 40

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

Answer 40

Replace thermocouple.

Question 41

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

Answer 41

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

Question 42

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

Answer 42

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

Question 43

Name two functions of a thermopile can perform.

Answer 43

Operate the safety system (power unit) | Operate the main burner gas valve (operating gas valve)

Question 44

A thermopile is a number of thermocouples connected in ____.

Answer 44

in SERIES.

Question 45

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

Answer 45

a 24-VOLT system

Question 46

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

Answer 46

Pull-in voltage test.

Question 47

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

Answer 47

An effective ignition test.