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Refrigeration 2nd Year > Controls Ft. T Frank > Flashcards

Controls Ft. T Frank Flashcards

1
Q

What does a closed loop control circuit do

A

Uses feedback to make control system automated

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2
Q

Purpose of an automatic gas valve

A
  • comfort
  • safely
  • economy
  • convenient
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3
Q

What does a pressure transducer sense?

A

Pressure than coverts to electrical signal

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4
Q

On a A19 temp controller feat position is B in?

A

Closes on a rise in temp heating

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5
Q

What does an anticipator do

A

Creates false load to prevent overshoot

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6
Q

Like voltage thermostat can be temporarily used in a millivolt application?

A

Yes

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7
Q

What’s in a mercury bulb thermostat

A

Bimetal coil and contactor

-must be carful levelled

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8
Q

Strip type sensor is used for what

A

Electric baseboard heating

- no anticipator

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9
Q

Natural gas “WC?

A

3.5”

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10
Q

How much power does a thermocouple make

A

30mv DC

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11
Q

What kind of power does flame rectification create?

A

DC micro amps

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12
Q

What is an anticipator in heating

A

A resistance wire in series with thermostat contacts

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13
Q

In heating is anticipator energized in the off cycle

A

No

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14
Q

Thermistor change in temp=

A

Change in resistance

Negative temperature

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15
Q

2nd Series if events for hearing

A

Pre purge

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16
Q

What makes a spiral sensing element more accurate

A

Increase length

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17
Q

Setting at LPC how long do you watch it for?

What temp can it not go below

A

2 cycles

33.5F

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18
Q

Direct Spark or hot surface igniter use flame rectification?

A

Yes

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19
Q

Is a resistor temp detector more accurate than a thermistor?

A

Yes

Can be positive or negative

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20
Q

A-19 is snap acting? Why?

A

Yes to avoid arking

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21
Q

How is an anticipator wired in a cooling cycle

A

In parallel

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22
Q

When does a constant cut in control cut in?

A

38F or 41F

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23
Q

Combination gas valve, must must be held open manually when lightning pilot?

A

Yes

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24
Q

When does the fan shut off

A

90-100F

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25
Q

Igniter warm up period?

A

17 seconds

26
Q

Do millivolt thermostats have anticipators?

A

No draws too much voltage drop

27
Q

What does open loop mean?

A

No feed back

Operates by time

28
Q

Power goes from where to where in furnace ac control

A

In from R to Y though the CC than to C

29
Q

Disadvantage of pump down?

A

Compressor could short cycle

Ex. Leaking solenoid, improperly set LPC

30
Q

Dry bulb is effected by
Humidity
Air movement
Radiation

A

Yes

31
Q

When does the fan turn on?

A

120-140F

32
Q

How long does inducer motor run after blower off?

A

15 seconds

33
Q

Call for heat terminals

A

R and W close

34
Q

Approximate settings if a high limit switch in the high voltage circuit?

A

180-200F

35
Q

Blower off delay what terminals?

A

Cr and W open

36
Q

Combination gas valve, how much power does the main valve need?

A

24VAC

37
Q

What is LVT cable

A

Extra low voltage cable

For thermostat wiring

38
Q

Why is a jumper factory installed

A

When cooling and heating use same control voltage

39
Q

Advantages of pump down?

A
  • No flooding the comp

- very good liquid refrigerant control

40
Q

I’m cooling when is the anticipator energized?

A

On the off cycle

41
Q

Combination gas valve, what is powers by the thermocouple

A
  • safety
  • power unit
  • pilot start
42
Q

What’s in a combination gas valve?

A
  • Regulator
  • safety valve
  • power unit
  • main gas valve
  • manual gas shut off
43
Q

What temp does AHRAE recommend for cooling

A

75F for cooling

44
Q

Does power from a thermocouple open the pilot valve?

A

No only holds it open

45
Q

What class of transformer do most furnaces have?

A

Class 2

46
Q

With a F-140-20 disk type overload what does the 140 mean and 20

A

140 is cut out

20 is differential cut in

47
Q

Checking volts in electrical circuit

A

Power is on and Meter in parallel

48
Q

Motor starters and contractors are different because

A

Motor starters have overloads

49
Q

Ad stages of hot water heating

A

Less space

Less air movement

50
Q

Hot water disadvantages

A

No ventilation

No air filtration/humidity control

51
Q

What so zone thermostats control

A

A pump or valve

52
Q

On mid efficient furnaces they need to maintain return water temp of ______ to prevent condensation

A

130

53
Q

Hot water, .43 psi pressure drop for upwards piping

A

Yes

54
Q

Can a mop txv and a cpr be together

A

No

55
Q

High limit is set at what fir hot water application

A

210F

56
Q

Hot water uses float type and electric for

A

Proving water flow and low water cut out

57
Q

Hot water expansion tank w no bladder is called a

A

Compression tank

58
Q

Make up water regulator is set between

A

10-25 Psi

59
Q

Can zone valves be power open abs power closed

A

Yes

60
Q

Transformer can only be loaded to

A

80%

Refrigeration 2nd Year (13 decks)

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