PLANT HVAC SYSTEMS

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PLANT HVAC SYSTEMS

• DU-109-PP

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PLANT HVAC SYSTEMS

• PURPOSE
• The purpose of the Operations and Maintenance
  Training Program is to train Operations and
  Maintenance Technicians in the operation of the
  Duke University Plant Heating, Ventilation, and
  Air Conditioning (HVAC) Systems.
• OBJECTIVES
• Trainees will demonstrate knowledge of
• HVAC System Components
• HVAC System Components Operation
• HVAC System Configuration
• HVAC System Controls and Instrumentation

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PLANT HVAC SYSTEMS

• PURPOSE
• The purpose of the Heating, Ventilation, and Air
  Conditioning (HVAC) System is to
• Provide heat and cooling climate control for
  plant, office/control room, and electrical room
  areas of the steam and chiller plants
• Maintain Interior Air Quality (IAQ)
• Maintain air pressure
• Provide emergency exhaust

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PLANT HVAC SYSTEMS

• HVAC AIR FUNCTIONS
• To understand how HVAC works, you need to be
  familiar with the six functions of HVAC air.
• Return Air
• Air inside the building drawn back into the air
  handlers
• Outside Air
• Fresh air drawn into the air handlers from
  outside
• Supply Air
• Air blown into the building from the air handlers

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PLANT HVAC SYSTEMS

• HVAC AIR FUNCTIONS
• Makeup Air
• Air blown into the building by Makeup Air Unites
  (MAUs) to maintain air pressure balance when
  pressure is low
• Relief Air
• Air exhausted from the building to maintain air
  pressure balance when air pressure is high
• Exhaust Air
• Air expelled to remove contaminants from areas
  where chemicals, hazardous materials, and toxic
  gases are present
• Air exhausted from the building in case of
  emergency

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PLANT HVAC SYSTEMS

• WHY AIR BALANCE IS IMPORTANT
• Over Pressure and Under Pressure conditions
  negatively affect building efficiency.
• Over Pressure
• When air pressure inside a building is higher
  than pressure outside, the conditioned air inside
  the building is pushed outside.
• High air pressure can require excess energy to
  condition the air in the building and compensate
  for energy lost.

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PLANT HVAC SYSTEMS

• WHY IS AIR BALANCE IMPORTANT?
• Under Pressure
• When building pressure is lower than pressure
  outside, the air outside is drawn inside.
• Outside air may come from undesirable sources
  (trash bins, open doors, cracks, construction,
  and so forth).
• Unfiltered or unconditioned air can affect the
  HVAC systems ability to maintain the desired
  environment.

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PLANT HVAC SYSTEMS

• QUESTION
• What does IAQ stand for?
• International Air Quality
• Industrial Air Quality
• Interior Air Quality
• In-duct Air Quality

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PLANT HVAC SYSTEMS

• ANSWER
• IAQ stands for Interior Air Quality.

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PLANT HVAC SYSTEMS

• QUESTION
• What kind of air is blown into building from air
  handlers?
• Return Air
• Outside Air
• Makeup Air
• Supply Air

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PLANT HVAC SYSTEMS

• ANSWER
• Supply Air is recirculated through the air
  handlers.

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PLANT HVAC SYSTEMS

• QUESTION
• What kind of air is added when air pressure is
  low?
• Return Air
• Outside Air
• Makeup Air
• Supply Air

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PLANT HVAC SYSTEMS

• ANSWER
• Makeup Air is blown into a building when air
  pressure is low.

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PLANT HVAC SYSTEMS

• QUESTION
• What causes Over Pressure?
• Pressure is higher on the lower level than on the
  mezzanine
• Pressure is lower in the building than outside
• Pressure is higher in the building than outside
• Pressure is lower on the lower level than on the
  mezzanine

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PLANT HVAC SYSTEMS

• ANSWER
• Over Pressure is the condition when pressure
  inside the building is higher than outside.

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PLANT HVAC SYSTEMS

• QUESTION
• What causes Under Pressure?
• Pressure is higher on the lower level than on the
  mezzanine
• Pressure is lower in the building than outside
• Pressure is higher in the building than outside
• Pressure is lower on the lower level than on the
  mezzanine

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PLANT HVAC SYSTEMS

• ANSWER
• Under Pressure is the condition when pressure
  inside the building is lower than outside.

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PLANT HVAC SYSTEMS

• PLANT HVAC COMPONENTS
• Air Handler Units (AHUs)
• Makeup Air Units (MAUs)
• Fan Coil Units (FCUs)
• Exhaust fans
• Supply fans
• Emergency exhaust fans

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PLANT HVAC SYSTEMS

• AHU COMPONENTS
• The Mixing Box section contains
• Return Air Damper which connects to the Return
  Air Duct
• The Relief Air Damper also connects to the Return
  Air Duct
• Outside Air Damper which connects to the duct to
  the building exterior

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PLANT HVAC SYSTEMS

• AHU COMPONENTS
• The Filter section contains
• Access door for filter element replacement
• W.C. Meter mounted in door
• Filter is replaced when air pressure reaches
  maximum resistance

RETURN AIR
W.C. METER
RELIEF AIR
OUTSIDE AIR
FILTER
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PLANT HVAC SYSTEMS

• AHU COMPONENTS
• The Cooling Coil section contains
• In and Out connections for chilled water
• Cooling coil heat exchanger

RELIEF AIR
RETURN AIR
OUTSIDE AIR
FILTER
COOLING COIL
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PLANT HVAC SYSTEMS

• AHU COMPONENTS
• The Heating Coil section contains
• In and Out connections for steam
• Heating coil heat exchanger

RETURN AIR
RELIEF AIR
COOLING COIL
OUTSIDE AIR
FILTER
HEATING COIL
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PLANT HVAC SYSTEMS

• AHU COMPONENTS
• The Fan section contains
• Fan and motor
• Starter Box mounted on exterior or nearby

RETURN AIR
OUTSIDE AIR
HEATING COIL
FILTER
COOLING COIL
MIXING BOX
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PLANT HVAC SYSTEMS

• QUESTION
• What is accomplished in the AHU mixing box?
• Return air is mixed with relief air
• Supply air is mixed with return air
• Supply air is mixed with outside air
• Return air is mixed with outside air

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PLANT HVAC SYSTEMS

• ANSWER
• Return air is mixed with outside air in the AHU
  mixing box.

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PLANT HVAC SYSTEMS

• QUESTION
• What kind of meter is mounted in the filter
  section door of an AHU?
• Temperature sensor
• Pressure gauge
• W.C. meter
• Anemometer

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PLANT HVAC SYSTEMS

• ANSWER
• A W.C. meter is mounted in the door of the filter
  section. The W.C. (Water Column) meter measures
  resistance through the filter in inches to
  indicate when the filter needs to be changed.

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PLANT HVAC SYSTEMS

• QUESTION
• Where is the starter box located for an AHU?
• Exterior of the fan section or nearby
• Mixing box
• Control Room
• AHUs do not need starters

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PLANT HVAC SYSTEMS

• ANSWER
• The starter box is mounted on the fan section of
  the AHU or nearby.

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PLANT HVAC SYSTEMS

• MAU COMPONENTS
• The Fan section contains
• Fan and motor
• Outside Air Damper which connects to the duct to
  the building exterior

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PLANT HVAC SYSTEMS

• MAU COMPONENTS
• The Coil section contains
• In and Out connections for steam and chilled
  water
• Heating and cooling coil heat exchangers

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PLANT HVAC SYSTEMS

• MAU COMPONENTS
• The Filter section contains
• Filters
• Supply Air Damper

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PLANT HVAC SYSTEMS

• MAU COMPONENTS
• The Starter box is located next to the MAU.

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PLANT HVAC SYSTEMS

• QUESTION
• What is one way an MAU differs from an AHU?
• The MAU takes in return air and outside air
• The MAU takes in relief air only
• The MAU takes in outside air only
• The MAU takes in return air only

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PLANT HVAC SYSTEMS

• ANSWER
• The MAU takes in outside air only.

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PLANT HVAC SYSTEMS

• QUESTION
• What does MAU stand for?
• Main Air Unit
• Maximum Air Unit
• Mini Air Unit
• Makeup Air Unit

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PLANT HVAC SYSTEMS

• ANSWER
• MAU stands for Makeup Air Unit.

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PLANT HVAC SYSTEMS

• QUESTION
• What is another way an MAU differs from an AHU?
• The MAU has a mixing box
• The MAU does not have a mixing box
• The MAU has a cooling coil
• The AHU has a cooling coil

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PLANT HVAC SYSTEMS

• ANSWER
• The MAU does not have a mixing box.

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PLANT HVAC SYSTEMS

• FCU COMPONENTS
• Outside Air Damper
• Electric Duct Heater

RETURN AIR
SUPPLY AIR
ELECTRIC DUCT HEATER
OUTSIDE AIR DAMPER
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PLANT HVAC SYSTEMS

• FCU COMPONENTS
• Filter
• Cooling Coil
• Fan and Motor

FAN
COOLING COIL
FILTER
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PLANT HVAC SYSTEMS

• QUESTION
• What does the FCU use to heat supply air?
• Steam
• Hot water
• Electricity
• Friction

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PLANT HVAC SYSTEMS

• ANSWER
• The FCU uses an Electric Duct Heater to heat air
  in the supply air duct.

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PLANT HVAC SYSTEMS

• QUESTION
• What does FCU stand for?
• Forced Cooling Unit
• Facilities Control Unit
• Furnace Coil Unit
• Fan Coil Unit

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PLANT HVAC SYSTEMS

• ANSWER
• FCU stands for Fan Coil Unit.

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PLANT HVAC SYSTEMS

• PLANT HVAC SYSTEMS CONFIGURATION AND PROCESS FLOW
• The flow for Chiller Plant 2 is used as an
  example.

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PLANT HVAC SYSTEMS

• CHILLER PLANT 2 AHU-21 SYSTEM
• Temperature Transmitters on the Return Air Duct,
  Supply Air Duct, and Mixing Box of AHU-21 send
  readings to the Local Controller Digital Control
  System (DCS).

AHU-21
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PLANT HVAC SYSTEMS

• CHILLER PLANT 2 AHU-21 SYSTEM
• The local DCS controls heating and cooling by
  modulating the Cooling Coil chilled water control
  valve and the steam valve supplying the Heating
  Coil.

COOLING COIL
HEATING COIL
MIXING BOX
CHILLED WATER CONTROL VALVE
STEAM VALVE
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PLANT HVAC SYSTEMS

• CHILLER PLANT 2 AHU-21 SYSTEM
• The Outside Air Damper is set at 2,000 CFM.
• The Return Air Damper is set at 30,000 CFM.

SUPPLY AIR DAMPER D-21E
AHU-21
MIXING BOX
OUTSIDE AIR DAMPER D-21F
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PLANT HVAC SYSTEMS

• CHILLER PLANT 2 AHU-21 SYSTEM
• 1,000 CFM exhausted continuously from Chemical
  Treatment area by Exhaust Fan EF-23.
• 350 CFM exhausted continuously from the Break
  Room, Mens and Womens Restrooms, Shower, and
  Janitors Closet by Exhaust Fan EF-24.

LOUVER L-28
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PLANT HVAC SYSTEMS

• CHILLER PLANT 2 AHU-21 SYSTEM
• Supply Fans SF-21 and SF-22 run continuously to
  recirculate air within the plant.

AHU-21
SUPPLY FAN SF-21
SUPPLY FAN SF-22
EF-24
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PLANT HVAC SYSTEMS

• CHILLER PLANT 2 AHU-21 SYSTEM
• Economizer Operation
• Based on outside air enthalpy and outside air
  temperature, when less than 60F AHU-21 operates
  in economizer cycle modulating the outside and
  return air dampers to maintain 60F supply air
  temperature.

RETURN AIR DAMPER
OUTSIDE AIR DAMPER
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PLANT HVAC SYSTEMS

• CHILLER PLANT 2 AHU-21 SYSTEM
• Economizer Operation
• The chilled water valve to AHU-21 is closed
  during economizer cycle.
• In the event of damper failure or mixed air
  temperature below 35F, a freezestat shuts down
  AHU-21 and sends an alarm.

FREEZESTAT
CHILLED WATER VALVE
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PLANT HVAC SYSTEMS

• CHILLER PLANT 2 AHU-21 SYSTEM
• Economizer Operation
• Relief Air Damper RD-21 is controlled by
  differential pressure to maintain a 0.05 inch
  W.C. positive pressure in the building by
  modulating the damper.

AHU-21
PRESSURE SENSOR A7 AT 0.05 W.C.
RELIEF DAMPER RD-21
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PLANT HVAC SYSTEMS

• CHILLER PLANT 2 AHU-21 SYSTEM
• Emergency Exhaust
• During emergency when refrigerant accumulates
  above 100 PPM due to leak or rupture, air
  recirculation dampers to Exhaust Fans EF-21 and
  EF-22 close and exhaust dampers open forcing the
  refrigerant from the building.

EMERGENCY EXHAUST DAMPER L-26
EMERGENCY EXHAUST DAMPER L-25
SOUTH EMERGENCY EXHAUST EF-22
NORTH EMERGENCY EXHAUST EF-21
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PLANT HVAC SYSTEMS

• CHILLER PLANT 2 AHU-21 SYSTEM
• Emergency Exhaust
• Supply Fans SF-21 and SF-22 shut down.
• The outside air damper to AHU-21 opens fully and
  the return air damper closes.
• Additional outside air (30,000 CFM) brought into
  the building from AHU-21 is exhausted through
  Positive Relief Damper RD-1.
• When the refrigerant detectors no longer sense a
  low refrigeration concentration of 100 PPM,
  exhaust air dampers to EF-21 and 22 close and the
  air recirculation dampers open. SF-21 and 22 then
  energize and AHU-21 returns to a modulating
  damper cycle.

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PLANT HVAC SYSTEMS

• CHILLER PLANT 2 AHU-21 SYSTEM
• Emergency Exhaust
• If an emergency occurs when the supply air
  temperature is less than 60F, a temperature
  sensor opens steam valve TCV-AHU-21B to maintain
  a supply air temperature of 60F.

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PLANT HVAC SYSTEMS

• QUESTION
• Based on outside air enthalpy and outside air
  temperature, what is the lowest temperature at
  which AHU-21 will operate before entering the
  economizer cycle?
• 80F
• 40F
• 60F
• 72F

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PLANT HVAC SYSTEMS

• ANSWER
• Based on outside air enthalpy and outside air
  temperature, when less than 60F AHU-21 operates
  in economizer cycle.

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PLANT HVAC SYSTEMS

• QUESTION
• When do Supply Fans SF-21 and SF-22 run?
• Only when building pressure is low
• Continuously
• Only when building pressure is high
• Only at night

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PLANT HVAC SYSTEMS

• ANSWER
• Supply Fans SF-21 and SF-22 run continuously to
  recirculate air within the plant.

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PLANT HVAC SYSTEMS

• QUESTION
• Where do the temperature transmitters on the
  ducts and mixing box on AHU-21 send readings?
• Local Controller DCS
• AHU-22
• Directly to the Control Room
• Chiller Plant 1

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PLANT HVAC SYSTEMS

• ANSWER
• Temperature Transmitters on the Return Air Duct,
  Supply Air Duct, and Mixing Box of AHU-21 send
  readings to the Local Controller Digital Control
  System (DCS).

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PLANT HVAC SYSTEMS

• CHILLER PLANT 2 AHU-22 SYSTEM
• AHU-22 supplies 10,000 CFM of cooling to the
  Electric Room.
• The local DCS modulates the cooling coil chilled
  water valve in response to temperature sensors in
  the supply and return air ducts and mixing box.

COOLING COIL
COOLING COIL CHILLED WATER VALVE TCV-AHU-22A
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PLANT HVAC SYSTEMS

• CHILLER PLANT 2 AHU-22 SYSTEM
• The Outside Air Damper is set at 9,940 CFM.
• 60 CFM is exhausted continuously through the
  Gravity Relief Damper in the mezzanine floor.

OUTSIDE AIR DAMPER L-23
AHU-22
GRAVITY RELIEF DAMPER RD-22
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PLANT HVAC SYSTEMS

• CHILLER PLANT 2 AHU-22 SYSTEM
• Economizer Operation
• Based on outside air enthalpy and outside air
  temperature, when less than 60F AHU-22 operates
  in economizer cycle modulating the outside and
  return air dampers to maintain 60F supply air
  temperature.

OUTSIDE AIR DAMPER
RETURN AIR DAMPER
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PLANT HVAC SYSTEMS

• CHILLER PLANT 2 AHU-22 SYSTEM
• Economizer Operation
• Relief Air Damper RD-21 is controlled by
  differential pressure to maintain a 0.05 inch
  W.C. positive pressure in the building by
  modulating the damper.

PRESSURE SENSOR A7 AT 0.05 W.C.
RELIEF DAMPER RD-21
AHU-22
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PLANT HVAC SYSTEMS

• CHILLER PLANT 2 AHU-22 SYSTEM
• Economizer Operation
• The chilled water valve to AHU-22 is closed
  during economizer cycle.
• In the event of damper failure or mixed air
  temperature below 35F, a freezestat shuts down
  AHU-22 and sends an alarm.

FREEZESTAT
CHILLED WATER VALVE
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PLANT HVAC SYSTEMS

• QUESTION
• What area is cooled by AHU-22?
• Control Room
• Janitors closet
• Chemical Treatment Area
• Electric Room

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PLANT HVAC SYSTEMS

• ANSWER
• AHU-22 cools the Electric Room.

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PLANT HVAC SYSTEMS

• QUESTION
• Where Is the Gravity Relief Damper located?
• Control Room
• Mezzanine floor
• Electric Room
• Operating floor

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PLANT HVAC SYSTEMS

• ANSWER
• The Gravity Relief Damper is in the mezzanine
  floor.

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PLANT HVAC SYSTEMS

• QUESTION
• What volume of cooling air is supplied to the
  Electric Room by AHU-22?
• 1,250 CFM
• 2,000 CFM
• 10,000 CFM
• 30,000 CFM

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PLANT HVAC SYSTEMS

• ANSWER
• AHU-22 supplies 10,000 CFM of cooling to the
  Electric Room.

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PLANT HVAC SYSTEMS

• CHILLER PLANT 2 FCU-21 SYSTEM
• FCU-21 supplies 1,285 CFM of cooling to the
  Control Room, break room, office, and vestibule.
• Cooling is controlled by modulating the cooling
  coil chilled water valve in response to a
  temperature sensor in the Control Room.

COOLING COIL CHILLED WATER VALVE FCU-21A
CONTROL ROOM
COOLING COIL
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PLANT HVAC SYSTEMS

• CHILLER PLANT 2 FCU-21 SYSTEM
• Outside air is set at 175 CFM during cooling with
  1,110 CFM of return air.
• Heating is provided by a 6 KW Electric Duct
  Heater located in the supply air duct.

ELECTRIC DUCT HEATER DH-21
FCU-21
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PLANT HVAC SYSTEMS

• QUESTION
• Where is the Electric Duct Heater located?
• In the return air duct
• In the supply air duct
• In the relief air duct
• In the makeup air duct

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PLANT HVAC SYSTEMS

• ANSWER
• The Electric Duct Heater is located in the supply
  air duct.

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PLANT HVAC SYSTEMS

• QUESTION
• Which of the following areas is cooled by FCU-21?
• Operating floor
• Chemical treatment area
• Electric Room
• Control Room

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PLANT HVAC SYSTEMS

• ANSWER
• FCU-21 supplies cooling to the Control Room,
  break room, office, and vestibule.

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PLANT HVAC SYSTEMS

• OPERATIONS MONITORING
• Operation of the Plant HVAC Systems is monitored
  through the Control Room on the top floor of
  Chilled Water Plant 2.

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PLANT HVAC SYSTEMS

• PLANT ROUNDS
• During an Operators routine shift, Rounds are
  accomplished to record key information and
  visually assess HVAC Water System operation.
• Each Plant has a Rounds Sheet to be filled out by
  the Operator.
• Each plant has different requirements for plant
  rounds.
• The information is recorded, not only for the
  current status, but also to record system trends.
  

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PLANT HVAC SYSTEMS

• EXAMPLE ROUNDS SHEET (front and back)

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PLANT HVAC SYSTEMS

• HVAC DAILY ROUNDS
• Chiller Plants 1 and 2
• Outside temperature
• Outside humidity
• Outside enthalpy
• AHU (On/Off)
• Supply Fans (On/Off)
• Exhaust Fans (On/Off)

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PLANT HVAC SYSTEMS

• HVAC DAILY ROUNDS
• West and East Campus Steam Plants
• Outside temperature
• AHU
• Online/Offline
• Space temperature
• Supply air temperature
• Supply Fan
• Online/Offline
• Space temperature
• Supply air temperature

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PLANT HVAC SYSTEMS

• HVAC DAILY ROUNDS
• West and East Campus Steam Plants
• Exhaust Fan (not all exhaust fans are checked for
  all conditions)
• Online/Offline
• Space temperature
• Supply air temperature
• Firm alarm OK
• Gas alarm OK
• E-Stop alarm OK

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PLANT HVAC SYSTEMS

• TYPICAL PROBLEMS ASSOCIATED WITH PLANT HVAC
  SYSTEMS
• Stuck dampers
• Most likely cause is corrosion or debris
• Blocked coils
• Most likely cause is corrosion, faulty filters
• Malfunctioning control components
• Components damaged or out of calibration
• Clogged condensate drains
• Most likely cause is debris or damage to pipes

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PLANT HVAC SYSTEMS

• QUESTION
• Where does Operations Monitoring take place?
• Control Room in each steam plant
• Control Room in West Campus Steam Plant
• Control Room in Chilled Water Plant 2
• Control Room in Chilled Water Plant 1

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PLANT HVAC SYSTEMS

• ANSWER
• Operations Monitoring takes place In the Control
  Room in Chilled Water Plant 2.

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PLANT HVAC SYSTEMS

• QUESTION
• Which air pressure condition in a building is
  preferable?
• Under Pressure
• Over Pressure
• Balanced
• Air pressure is not a concern of HVAC

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PLANT HVAC SYSTEMS

• ANSWER
• Operations Monitoring takes place In the Control
  Room in Chilled Water Plant 2.