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Level 2: Control Fundamentals > Honeywell Pneumatics Exercise > Flashcards

Honeywell Pneumatics Exercise Flashcards

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1
Q

Name 5 functions of a pneumatic hvac system control?

A
  1. fan coils
  2. VAV boxes
  3. perimeter fin tube heat
  4. roof tops
  5. unit ventilators
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2
Q

Why must the pneumatic air supply be dry and clean?

A

T-stats and actuators have small orifices

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3
Q

What is required on an air compressor to prevent moisture?

A

auto drain valve or manually relieve the water

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4
Q

What causes the water to condensate in the air compressor

A

higher pressure change condensing temp causing water to separate

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5
Q

Name two ways of drying the air?

A
  1. Refrigerated air dryers

2. Dessicants

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6
Q

What components are in the PRV/filter station?

A
  1. filter
  2. drain cock
  3. PRV
  4. tank
  5. supply air gauges
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7
Q

What type controller are the thermostats in a pneumatic system?

A

inherently modulating

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8
Q

On a thermostat, what pressure does the air modulate between?

__psi and 13psi

A

3psi and 13psi

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9
Q

Typically, what is the main air pressure supply?

A

approximately 18psi

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10
Q

What is the Nozzle-flapper assembly?

A

provides a modulated air bleed

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11
Q

What is the name of the line between the thermostat and the actuator?

A

branch

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12
Q

What is the purpose of the bimetal in the thermostat?

A

as temp changes the strip will move allowing the flapper to release air or allow press to build up

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13
Q

What are pneumatic relays used for?

A

to manipulate pneumatic control signal for sequence of operation

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14
Q

What forces move the push rod open and closed?

A

open- air pressure

closed - spring

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15
Q

What type of construction are the actuators?

A

rolling diaphragm

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16
Q

Explain how a damper is considered normally open or normally closed?

A

if the actuator return spring drives the damper open or closed at 0psi

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17
Q

What is another term used to describe normally open or normally closed?

A

fail position

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18
Q

What air pressure is required to extend the shaft 1/2” on 8 to 12psi range?

A

10psi

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19
Q

What is the term used to describe the distance a shaft will move?

A

the stroke

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20
Q

What two valve body types are used?

A
  1. direct acting

2. reverse acting

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21
Q

What position is the stem in a reverse acting valve when it is open?

A

stem is down

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22
Q

What position is the stem in a direct acting valve when it is closed?

A

stem is down

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23
Q

When a spring is added in a direct acting actuator, what position is the stem?

A

normally retracted stem

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24
Q

When a spring is added in a reverse acting actuator what position is the stem?

A

normally extended stem

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25
Q

In a normally open valve what Is the air pressure required to open a RA type valve?

A

0psi

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26
Q

In a normally closed valve what is the air pressure required to close a DA type valve?

A

0psi

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27
Q

What does the spring range determine?

A

start and stop of the valve stroke

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28
Q

What is important to for the valve to close off 100%?

A

enough closing torque

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29
Q

What does a valve positive positioner prevent?

A

eliminates disk float

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30
Q

What can be added to use electricity to control the valve?

A

DDC controller

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31
Q

Why add a DDC controller?

A

economical during an upgrade, actuators can remain in place

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32
Q

What is better about a pneumatic actuator?

A

better torque

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33
Q

What pressure is seen when the filter element needs to be replaced?

A

10psi

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34
Q

What should be checked before calibrating a thermostat?

A

ensure you have enough main pressure, 18-20psi

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35
Q

What does the bimetal respond to?

A

room temp

36
Q

What are the terminals labeled on a two pipe thermostat and what pipe on each terminal?

A

M - main

B- branch

37
Q

By bleeding of air, how does this affect the actuator?

A

causes the actuator to modulate

38
Q

Where is the resistor located in a one pipe thermostat?

A

internally inside the thermostat

39
Q

Where is the restrictor located in a single pipe installation?

A

in the main line before the thermostat

40
Q

What material is used for piping air lines?

A

old days copper modern plastic tube

41
Q

How does a low capacity thermostat thermostat effect the actuator?

A

same power but slower reaction time

42
Q

What is the throttling range?

A

is the change in degrees that will cause the valve/damper to go from full open to full close

43
Q

What is set point?

A

desired temp

44
Q

What is control point?

A

current room or space temp

45
Q

What its the difference between the set point and control point called?

A

offset

46
Q

If a thermostat has a throttling range of 4 degrees and the set point is 68 F. What position will the valve be in at 66F in cooling mode (chilled water)?

A

fully closed

47
Q

If a thermostat has a throttling range of 4 degrees and the set point is 68F. What position will the valve be in at 74F in cooling mode? (chilled water)

A

fully open

48
Q

If a thermostat has a throttling range of 3 degrees and the set point is 72F. What position will the valve be in at 74F in cooling mode? (hot water)

A

fully open

49
Q

What causes the room temperature to drop below the thermostat set point?

A

heat loss, if the heat loss is greater than the heat supplied

50
Q

How does proportional control compensate for high heat loss?

A

opens the valve more to allow more heat to enter the space

51
Q

What will a small throttling range cause?

A

the system to hunt causing under and overshoots

52
Q

Where is throttling range adjusted?

A

At the thermostat. True for DDC systems as well

53
Q

Why is it important to check the calibration of a thermostat?

A

To maintain the temp at the correct setting

54
Q

How do you calibrate your temperature measuring device?

A

Ice or boiling water

55
Q

What is the recommended main air pressure?

A

17-20psig

56
Q

What should you check for if the main air pressure is low?

A

leaks, kinks, air blockage, regulator set too low

57
Q

What should be done before you leave after calibrating a thermostat?

A

ensure actuator is responding then set T-stat to normal room setting

58
Q

What is a two temperature thermostat used for?

A

two temperature set points, day and night or heating and cooling

59
Q

How does the thermostat switch from day to night?

A

by changing main air pressure from high to low

set back

60
Q

What type of PRV is required and what other component is needed?

A

dual pressure PRV and electric pneumatic relay

61
Q

What components are used if using the alternate PRV method?

A

two PRV’s, an E/P relay which diverts air from A to C high press or B to C low press

62
Q

How many bimetal strips and flappers are in this thermostat?

A

two of each and both must be calibrated

63
Q

When is it recommended to check the calibration of a thermostat?

A

yearly scheduled maintenance, maybe twice a year for heating and cooling

64
Q

Why is it important to check the calibration of a thermostat?

A

check if they are measuring the proper temperature, check for wear and tear, check valves

65
Q

Can a defective stat be repaired by calibrating?

A

more than likely no

66
Q

What type of stat are combo coils used in?

A

heating and cooling

67
Q

Name 6 types of relays in a pneumatic system?

A
  1. capacity relay
  2. variable pressure switch
  3. air flow relays & controllers
  4. reversing relay
  5. pneumatic to electric relay
  6. sequencing/ratio relay
68
Q

Name 8 port designations

A
  1. main
  2. branch
  3. input
  4. n.o
  5. common
  6. n.c
69
Q

in a heat cool thermostat what does the thermostat do when switching between heating and cooling?

A

reverse acting for cooling and direct acting in heating

70
Q

What is an EP valve and what is it’s function?

A

electric to pneumatic, used to divert air

71
Q

What voltages are used in a E/PT?

A

2-10 volts DC

72
Q

How does the PE relay work?

A

as the pressure in the bellows change it will move a lever causing a switch to open or close

73
Q

Name uses of a P/E?

A

turn on or off pumps, fan coils, day night control, electric heaters

74
Q

What does a selector relay do?

A

can allow the higher or lower of the two pressures to pass through

75
Q

How can a selector be used in a zoning system?

A

by selecting the highest signal to determine heating or cooling

76
Q

How many thermostats can be attached to a RP913A load analyzer?

A

up to 7 inputs

77
Q

What device should be added (checked on an analyzer?

A

an air filter, 1psi differential you must replace

78
Q

Explain the operation of a switching relay?

A

as pressure changes in the pilot port, air will move from common port to normally connected or disconnected port

79
Q

What is a capacity relay used for?

A

increase strength of an input signal

80
Q

Explain minimum position?

A

minimum a valve or damper will close without closing 100%

81
Q

Explain maximum position?

A

maximum a valve or damper will open without opening 100%

82
Q

What application would a minimum position be applied?

A

fresh air dampers so there is always a certain amount of fresh air entering the building

83
Q

What controller an be used in a VAV box to control air flow?

A

velocity controller

84
Q

When are summer/winter thermostats used?

A

when reverse acting for heating and direct acting for cooling

85
Q

When is the electric heat strip used and why?

A

only during summer to temper chilled air and not in winter because of high operating costs

Level 2: Control Fundamentals (7 decks)

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