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Hi > Gas - Unit M > Flashcards

Gas - Unit M Flashcards

1
Q

List the four electrical circuits on a forced warm-air furnace.

A

Combustion safety circuit.

Control circuit[][][][][][][][][][][]

Fan circuit[][][][][][][][][][][][][]]

Transformer circuit[][][][][][]]

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2
Q

True or False?

All control systems have these four basic circuits:

Combustion Safety Circuit.

Control Circuit[][][][][][][][][][][]

Fan Circuit[][][][][][][][][][][][][][]]

Transformer Circuit[][][][][][][][]

A

False.

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3
Q

Identify the basic components of a Combustion Safety Circuit.

A

Safety shut off valve (switch).

Thermocouple[][][][][][][][][][][][][]

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4
Q

How many volts are generated by a single thermocouple?

A

25 - 30 mV.

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5
Q

Describe a thermopile and list the two types.

A

When one or more thermocouple is wired in series, the unit is called a thermopile. Coaxial and Modern.

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6
Q

Describe the difference between 100% safe switches and non-100% safe switches.

A

100% Safe: Shut off gas to burner and pilot.

Non-100% Safe: Shut off gas to burner[][][][]]

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7
Q

True or False?

Safety switches are commonly used on equipment having an input of over 400 cu ft/h.

A

True.

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8
Q

Explain why switches are always put in the hot leg of a circuit.

A

If in the hot leg, there will be no electricity connected to the appliance and no shock hazard when working on appliance when switch is off.

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9
Q

True or False?

A single pole, single throw switch can energize one of two different circuits or loads.

A

False.

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10
Q

True or False?

A double pole, single throw switch can open and close two independent circuits at the same time.

A

True.

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11
Q

True or False?

A normally open flow switch is open when current flows.

A

False.

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12
Q

True or False?

The high-limit switch is a normally closed switch that opens if overheating occurs.

A

True.

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13
Q

True or False?

An operating aquastat senses water temperature and de-energizes the main gas valve when the tempurature reaches the set point.

A

True.

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14
Q

True or False?

A high-limit aquastat is a back up to the operating aquastat but is adjusted to a higher set point.

A

True.

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15
Q

What will happen if the voltage designation of the gas valve’s magnetic coil does not match the power supply?

A

The valve coil may burn out or not operate the valve.

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16
Q

True or False?

A transformer is only used on alternating current.

A

True.

17
Q

True or False?

The primary and secondary coils of a transformer are not electrically connected.

A

True.

18
Q

True or False?

The primary and secondary coils of a transformer are magnetically connected.

A

True.

19
Q

True or False?

In a step-down transformer, the secondary coil has less voltage than the primary.

A

True.

20
Q

True or False?

In a step-down transformer, the secondary coil has more turns than the primary.

A

False.

21
Q

What is the rating of a transformer that drops voltage from 110V to 24V with an ouput of 3 1/3 amps?

A

24 Volts x 3 1/3 Amps = 80 VA.

22
Q

True or False?

The rating of a transformer should be less than the load to which it is attached.

A

False.

23
Q

True or False?

The fan switch turns on the fan as soon as the thermostat calls for heat.

A

False.

24
Q

True or False?

The fan switch is activated by heat.

A

True.

25
Q

True or False?

The fan-on set point tempurature will be reached some time after the gas valve opens.

A

True.

26
Q

True or False?

The fan-off set point tempurature will turn off the fan if the furnace gets too hot.

A

False.

27
Q

True or False?

The fan-off set point will be reached after the gas valve closes.

A

True.

28
Q

True or False?

When the fan-off set point is reached, the fan stops.

A

True.

29
Q

True or False?

If the motor pulley on a belt drive fan motor is made larger, the fan will run faster and deliver more air.

A

True.

30
Q

List four types of electrical drawings.

A

Block and one-line.

Pictorial[][][][][][][][][][]

Schematic[][][][][][][][]

Wiring[][][][][][][][][][][]]

31
Q

Which type of drawing shows the components of an electrical circuit in their actual likeness?

A

Pictorial.

32
Q

Which type of drawing shows electrical components as blocks and arranges them in a logical sequence of events?

A

Block and one-line.

33
Q

Which type of drawing is considered to be a map of the circuits?

A

Wiring.

34
Q

Which type of drawing shows the electrical relationship between the components in a circuit?

A

Schematic.

35
Q

Which type of drawing uses symbols to represent the switches and loads and shows each circuit as a rung of a ladder?

A

Ladder.

36
Q

List the components of an appliance branch circuit.

A

Appliance dissconnect switch.

Appliance junction box[][][][][][][]

Breaker (overcurrent protection device).

37
Q

Describe the two types of circuit breakers.

A

Magnetic.

Thermal[]

38
Q

To dissconnect power from the appliance in an emergency or for service and repair is the definition of?

A

Disconnect switch.

39
Q

To provide an approved location to join line voltage wiring is the definition of?

A

Junction box.

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