Honeywell Pneumatics Exercise Flashcards
Name two ways of drying the air?
- Refrigerated air dryers
- desiccants
2. Dessicants
What components are in the PRV/filter station?
- filter
- drain cock
- PRV
- tank
- supply air gauges
What type controller are the thermostats in a pneumatic system?
inherently modulating
Typically, what is the main air pressure supply?
approximately 18psi
What is the name of the line between the thermostat and the actuator?
branch
What is the purpose of the bimetal in the thermostat?
as temp changes the strip will move allowing the flapper to release air or allow press to build up
What are pneumatic relays used for?
to manipulate pneumatic control signal for sequence of operation
What forces move the push rod open and closed?
open- air pressure
closed - spring
What type of construction are the actuators?
rolling diaphragm
Explain how a damper is considered normally open or normally closed?
if the actuator return spring drives the damper open or closed at 0psi
What is another term used to describe normally open or normally closed?
fail position
What position is the stem in a reverse acting valve when it is open?
stem is down
What position is the stem in a direct acting valve when it is closed?
stem is down
When a spring is added in a direct acting actuator, what position is the stem?
normally retracted stem
When a spring is added in a reverse acting actuator what position is the stem?
normally extended stem
What does the spring range determine?
start and stop of the valve stroke
What is important to for the valve to close off 100%?
enough closing torque
What does a valve positive positioner prevent?
eliminates disk float
What can be added to use electricity to control the valve?
DDC controller
What is better about a pneumatic actuator?
better torque
What pressure is seen when the filter element needs to be replaced?
10psi
What should be checked before calibrating a thermostat?
ensure you have enough main pressure, 18-20psi
What does the bimetal respond to?
room temp
What are the terminals labeled on a two pipe thermostat and what pipe on each terminal?
M - main
B- branch
By bleeding of air, how does this affect the actuator?
causes the actuator to modulate
Where is the resistor located in a one pipe thermostat?
internally inside the thermostat
Where is the restrictor located in a single pipe installation?
in the main line before the thermostat
What material is used for piping air lines?
old days copper modern plastic tube
How does a low capacity thermostat thermostat effect the actuator?
same power but slower reaction time
What is the throttling range?
is the change in degrees that will cause the valve/damper to go from full open to full close
What is set point?
desired temp
What is control point?
current room or space temp
What its the difference between the set point and control point called?
offset
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)?
fully closed
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)
fully open
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)
fully open
What causes the room temperature to drop below the thermostat set point?
heat loss, if the heat loss is greater than the heat supplied
How does proportional control compensate for high heat loss?
opens the valve more to allow more heat to enter the space
What will a small throttling range cause?
the system to hunt causing under and overshoots
Where is throttling range adjusted?
At the thermostat. True for DDC systems as well
Why is it important to check the calibration of a thermostat?
To maintain the temp at the correct setting
How do you calibrate your temperature measuring device?
Ice or boiling water
What is the recommended main air pressure?
17-20psig
What should you check for if the main air pressure is low?
leaks, kinks, air blockage, regulator set too low
What should be done before you leave after calibrating a thermostat?
ensure actuator is responding then set T-stat to normal room setting
What is a two temperature thermostat used for?
two temperature set points, day and night or heating and cooling
How does the thermostat switch from day to night?
by changing main air pressure from high to low
set back
What type of PRV is required and what other component is needed?
dual pressure PRV and electric pneumatic relay
What components are used if using the alternate PRV method?
two PRV’s, an E/P relay which diverts air from A to C high press or B to C low press
How many bimetal strips and flappers are in this thermostat?
two of each and both must be calibrated
When is it recommended to check the calibration of a thermostat?
yearly scheduled maintenance, maybe twice a year for heating and cooling
Why is it important to check the calibration of a thermostat?
check if they are measuring the proper temperature, check for wear and tear, check valves
What type of stat are combo coils used in?
heating and cooling
Name 6 types of relays in a pneumatic system?
- capacity relay
- variable pressure switch
- air flow relays & controllers
- reversing relay
- pneumatic to electric relay
- sequencing/ratio relay
Name 8 port designations
- main
- branch
- input
- n.o
- common
- n.c
in a heat cool thermostat what does the thermostat do when switching between heating and cooling?
reverse acting for cooling and direct acting in heating
What is an EP valve and what is it’s function?
electric to pneumatic, used to divert air
What voltages are used in a E/PT?
2-10 volts DC
How does the PE relay work?
as the pressure in the bellows change it will move a lever causing a switch to open or close
Name uses of a P/E?
turn on or off pumps, fan coils, day night control, electric heaters
What does a selector relay do?
can allow the higher or lower of the two pressures to pass through
How can a selector be used in a zoning system?
by selecting the highest signal to determine heating or cooling
How many thermostats can be attached to a RP913A load analyzer?
up to 7 inputs
What device should be added (checked on an analyzer?
an air filter, 1psi differential you must replace
Explain the operation of a switching relay?
as pressure changes in the pilot port, air will move from common port to normally connected or disconnected port
What is a capacity relay used for?
increase strength of an input signal
Explain minimum position?
minimum a valve or damper will close without closing 100%
Explain maximum position?
maximum a valve or damper will open without opening 100%
What application would a minimum position be applied?
fresh air dampers so there is always a certain amount of fresh air entering the building
What controller an be used in a VAV box to control air flow?
velocity controller
When are summer/winter thermostats used?
when reverse acting for heating and direct acting for cooling
When is the electric heat strip used and why?
only during summer to temper chilled air and not in winter because of high operating costs
