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Copyright © Carrier Corp.
COMMERCIAL HVAC EQUIPMENTCentral Station
Air Handlers
PRESENTED BY:
Rodrigo L Valdez, Jr.
Sigler
Technical Development Program
Copyright © Carrier Corp.
Technical Development Program
Copyright © Carrier Corp.
Technical Development Program
Copyright © Carrier Corp.
Technical Development Program
Copyright © Carrier Corp.
• Identify different types of air handlers
• Categorize air handler construction methods
• Identify major air handler components
• Compare the difference between indoorand outdoor units
• Identify coil types
• Recognize types of fans used
• Identify unit accessory sections and theiruse
Objectives
Section 1 – Introduction
Copyright © Carrier Corp.
• Air Movement (Circulation)
• Cool and Dehumidified Air
• Heating
• Clean Air via Filtration
• Control of Space Humidity
• Means of Mixing Outside Air and Return Air
• Humidification in Winter
AHRI 430 Definition
Section 1 – Introduction
Copyright © Carrier Corp.
EADamper
SAFan
Where does the AHU fit in?
RAFan RA
Grille
Water Chiller
Water Piping
ChilledWaterPump
FilterOADamper
Coil
OUTDOORAIR
RA Damper
RA Duct
SADiffuser
COOLAIR
EXHAUSTAIR
SA Duct
HEAT
Section 1 – Introduction
AirHandler
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3 Types of Air Handling Units
Packaged, Central Station, and Custom
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Packaged AHU
Characteristics
• Fixed fan and coil configuration
• Limited to <12,000 cfm (30 tons)
• Split Cooling, CW or Heat Pumps
• Low-static < 2 in. ESP
• Indoor applications
Section 2 – Packaged, Central, and Custom AHU
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Packaged AHU’s Lack Flexibility
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Central Station AHUCharacteristics• Often referred to as “Applied”
or “Built-Up” systems.• Configured in a “Building
Block” fashion. Hundreds ofcomponent combinations
• Typical sizes range from1,500 to 50,000 cfm,although AHU”S capable ofdelivering 300,000 cfm areavailable.
• Multiple arrangements, fan,and coil types.
• Wide range of component options.• Indoor or outdoor models
Section 2 – Packaged, Central, and Custom AHU
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AHU Building Blocks
Section 2 – Packaged, Central, and Custom AHU
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Central Station AHU
Section 2 – Packaged, Central, and Custom AHU
START WITH THE FAN SECTION ANDMOVE UPSTREAM…
BUILDING BLOCK CONFIGURATION….
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Central Station AHUAdd additionalmodules forcoils, filter,mixing box,plenum orother asrequired tomeet theneeds of theproject..
Section 2 – Packaged, Central, and Custom AHU
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Central Station AHU
Section 2 – Packaged, Central, and Custom AHU
BUILT-UP AIR HANDLING UNIT WITH ECONOMIZER,FILTER SECTION, HEATING COIL, ACCESS SECTION,
COOLING COIL, AND FAN SECTION.
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Custom Air Handler
Key Features:• Job-Specific
Design– Dimensions
– Performance
– Materials
– Flexible
– More Expensive
Section 2 – Packaged, Central, and Custom AHU
• Used when standard unit designs cannot be applied.
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Custom Air Handler
Key Features:• Can match existing
footprint. Offergreatest flexibility.
Section 2 – Packaged, Central, and Custom AHU
•Aspect Ratio Changes
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Custom Air Handler
Key Features:• Specialty Fans
– Multiple Fans orFan Array
– Direct Drive
– Fan Wheel Type
Section 2 – Packaged, Central, and Custom AHU
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Custom Air Handler
Key Features:• Options not
normally found instandard centralstation airhandlers.– Factory-Installed,
job-specificcontrols
– Specialtycomponent notcataloged
Section 2 – Packaged, Central, and Custom AHU
Copyright © Carrier Corp.
Custom Air Handler
Key Features:• Used where
special casings areneeded.– Stainless steel
for corrosionprotection.
– Aluminum panelsfor weightreduction.
Section 2 – Packaged, Central, and Custom AHU
Copyright © Carrier Corp.
The relationship between airflow volume (cfm),velocity (V) and area (A) is:
cfm = V*A or A = cfm/V
Solution: A = cfm / VA = 25,000 cfm / 500 fpmA = 50 ft2 cooling coil required
Air Handler Nominal Size Selection
H
L
Section 2 – Packaged, Central, and Custom AHU
Where:A = H * L
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Coil Size & Face VelocityDetermine Max CFM
•FCS•LCS
•AIRFLOW
•ACC•HVF•MXB
•MIXING•BOX
•HIGH•VEL
•FILTER
•ACCESS•SECTION •COIL(S)
•SECTION •FAN
•39M03 = 3.5 SQ. FT. x 550 = 1,925 CFM
•39M06 = 5.9 SQ. FT. x 550 = 3,245 CFM
•39M08 = 7.6 SQ. FT. x 550 = 4,180 CFM
Copyright © Carrier Corp.
Copyright © Carrier Corp.
Basic Construction
CENTRAL STATION AIRHANDLERS
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Casing Construction - Post and Panel
Frame Rail
Double Wall Panel
Section 3 – Basic Construction
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• Uses load-bearing side wall panels• Individual panels may generally be removed, but not all at once• Allows manufacturers to vary wall thickness more easily
Structural Panel Construction
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Casing Design and Materials
• Galvanized steel most common.– Indoor units use a minimum of G-60– Outdoor units use a minimum of G-90
• Painted galvanized steel is recommendedfor outdoor air handlers, and optional forindoor units
• Alternate inner casing materials areavailable and used in response to indoorair quality concerns.
Section 3 – Basic Construction
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• 1-inch foil-faced insulation reducesthe potential for mold or bacteriaand is easier to clean
• 1-inch matte-faced fiberglass
Insulation - Single Wall Units
Section 3 – Basic Construction
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Double-Wall
Section 3 – Basic Construction
Copyright © Carrier Corp.
Thermal-Break ConstructionAn air handler construction feature thatprevents a conduction path of heat transferfrom the inside to the outside of the unit.Without this, sweating can occur at pointswithout thermal breaks.
PVC Panel FramePVC Panel Frame(no conduction path)
Casing Thermal Break
No metal-to-metal contactbetween frame and panelNo metal-to-metal contactbetween inner and outercasing
Section 3 – Basic Construction
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Casing Strength
MAX Deflection (D/L) = 1:200
Section 3 – Basic Construction
Casing Strength = Leak-Tight Integrity,
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Unit should have high quality seals on allpanel joints, section flanges, doors andaccess panels.
Seals:l Minimize air leakagel Prevent dirt and contaminants
from being drawn into the systeml Save energyl Reduce noise
Casing Seals
Section 3 – Basic Construction
Copyright © Carrier Corp.
Copyright © Carrier Corp.
Unit Types
CENTRAL STATION AIRHANDLERS
Copyright © Carrier Corp.
AHU - Horizontal, Vertical, Stacked
Section 4 – Unit Types
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Suspended units• Locate units over NON-critical spaces
to prevent:– Water leaks that could damage
sensitive equipment or materials– Sound that could be
objectionable– Restricted service
access
Floor-mounted units• AHU must be elevated enough to
allow for condensate drain trapping• Factory-supplied base rails
(full perimeter recommended)
Base Rail or Housekeeping Pad
Unit Mounting Considerations
RecommendedInline Beam Mount
Section 4 – Unit Types
Copyright © Carrier Corp.
Outdoor UnitsDesign Features:
• Painted casings• One-piece design• Sloped roof with overhangs• Double-wall with 2-inch minimum
wall thickness to minimize thermalheat transfer and casing sweating Outdoor
Air Hood
SlopedRoof
Section 4 – Unit Types
Copyright © Carrier Corp.
Draw-Thru• Fan downstream of cooling coil• Fan motor heat travels to
conditioned space, becomingroom load
Advantages:• Even airflow assured over the coil• Shortest length required
Draw-Thru and Blow-Thru
Horizontal Draw-Thru Horizontal Blow-Thru
Vertical Draw-Thru
Blow-Thru• Fan upstream of cooling coil• Fan blows air through coil• Diffuser plate needed – which
adds length
Advantages:• Motor heat becomes coil load
– NOT ROOM LOAD• Less cfm required with
smaller ducts andless fan energy
CoilCoil CoilCoil
CoilCoil
Section 4 – Unit Types
Copyright © Carrier Corp.
Coils
CENTRAL STATION AIRHANDLERS
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Copyright © Carrier Corp.
Cooling Coil Section
Mounting Rails
Sloped Drain Pan
WaterConnections
Section 5 – Coils
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Cooling Coils• Types
– Chilled water (CW)– Direct expansion (DX)– Variety of rows,
fin spacing, and splits• Materials (Common)
– Plate fins• Aluminum• Copper
– Copper tubes• Multiple wall thicknesses
• Casings– Galvanized steel– Stainless steel
Section 5 – Coils
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• Multiple circuiting options:– Quarter, full, half, double– Allow a wide application range– Allow proper oil return at part load
• Coil Splits– Intertwined Row– Face Split– Allow flexibility for part load control
Feeder Tubes
Suction Headers
RefrigerantDistributors
DX Coil Details
Section 5 – Coils
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Plate Fin Chilled Water CoilCooling Coils
• Plate fins mechanically bonded to tubes– Copper Tubes– Aluminum or Copper fins
• Multiple row options: 4 to 10 row typical• Fin spacing options: typically 8 to 14 fins/inch
Section 5 – Coils
Copyright © Carrier Corp.
Sloped Drain Pan• ASHRAE 62 requires
sloped drain pans thatdrain completely withno standing water
• Can be galvanizedor stainless steel
• Can be coated withantimicrobial compounds
Cooling Coil Sections
Section 5 – Coils
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Fan Characteristics and Performance
CENTRAL STATION AIRHANDLERS
Copyright © Carrier Corp.
Copyright © Carrier Corp.
Supply Fan
SA Fan
Draw-ThruCoilCoil
Blow-Thru
CoilCoil
SA Fan
Section 6 – Fan Characteristics and Performance
DiffuserPlate
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Return Fans
• Prevents excessive building pressurization• Used in systems with high return duct pressure drops• Generally controlled by building pressure sensor or
tracks the supply fan on VAV systems
RA Fan SA Fan
CoilCoil
Section 6 – Fan Characteristics and Performance
Copyright © Carrier Corp.
• Prevent excessive building pressurization
• Operates only during “economizer mode” or when ahigh percentage of ventilation air is being drawn in
Exhaust Fans
EXH Fan SA Fan
CoilCoil
Section 6 – Fan Characteristics and Performance
Copyright © Carrier Corp.
Characteristics:• Most commonly used wheel in HVAC• Light weight – lowest cost• Operates at static pressures up to 5 in. wg max.• Low rpm (800 to 1200 rpm)
Forward-Curved Wheel Design
Section 6 – Fan Characteristics and Performance
Copyright © Carrier Corp.
Characteristics:• Aerodynamically designed – double thickness airfoil shape for maximum
efficiency• For medium to high air capacity and pressure applications (4 to 10 in. wg)• Higher cost
Airfoil Wheel Design
Section 6 – Fan Characteristics and Performance
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Characteristics:• Pressurize a plenum chamber.• Operates at static pressures up to 10 in. wg• Flexibility to connect multiple outlet ducts
FanWheelGuard
InletCone
Plenum Fans (SWSI)
Section 6 – Fan Characteristics and Performance
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• Inlet Guide Vanes
• Discharge Dampers
• Variable Frequency Drives
VAV Airflow Control Options
Section 6 – Fan Characteristics and Performance
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Inlet Guide Vanes
Actuator Shaft(actuator not
shown)
Fan BearingLube Line for
Bearing
Inlet Vanes
Section 6 – Fan Characteristics and Performance
•Dampers on inlet reduce fan capacity
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Discharge DampersDampers are typically mounted close to or right off the fan discharge.
Remote DuctStatic Pressure
Sensor
DischargeDampers
SP
Section 6 – Fan Characteristics and Performance
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Variable Frequency Drives (VFDs)
Section 6 – Fan Characteristics and Performance
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Fan Modulation Methods
% Design Airflow
Inlet GuideVanes
%D
esig
nbh
p
VFD Speed Control
Discharge Dampers
Section 6 – Fan Characteristics and Performance
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VAV Applications
• It’s important to checkyour VAV fanselections at theminimum operatingpoint for stability.
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AMCA Fan Construction Class
Section 6 – Fan Characteristics and Performance
Tota
lSys
tem
Stat
icPr
essu
re(in
.wg)
Outlet Velocity (fpm)
Based onSP andoutletvelocity.
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Fan Components
• Fan Mounting
• Discharge Isolation
• Bearings
• Drives
• Motors
Section 6 – Fan Characteristics and Performance
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Standard 2-inchSteel Spring Isolator
Fan Spring Isolation
Section 6 – Fan Characteristics and Performance
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Discharge Isolation
Traditional Canvas Connector
Section 6 – Fan Characteristics and Performance
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Fan Discharge Vibration Isolation
Section 6 – Fan Characteristics and Performance
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Hours and Years
How long is 200,000 hours? The following tableconverts hours to years based on different daily usage.
HoursYears
8 hoursper day
16 hoursper day
Continuousduty
40,000 13.7 6.8 4.6
100,000 34.2 17.1 11.4
200,000 68.4 34.2 22.8
400,000 137 68.4 45.8
500,000 171 85.6 57.0
1,000,000 342 171 114
Bearings
Typical Pillow Block Bearing
Grease Fitting
Section 6 – Fan Characteristics and Performance
Operating Life Rating
Example = L50, L10…
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• Belt drive is most commonon central station units– Adjustable pitch for low bhp– Fixed-pitch for bhp >15
• Drive losses typically 3 to 5%
• More AHU’s today are usingdirect drives to reduce thecost of maintenance andeliminate belt residue
Motor and Drive Arrangement
Section 6 – Fan Characteristics and Performance
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Totally EnclosedFan-Cooled
(TEFC) Motor
Open Drip Proof(ODP) Motor
Fan Motor Types
Section 6 – Fan Characteristics and Performance
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Unit Accessories
CENTRAL STATION AIRHANDLERS
Copyright © Carrier Corp.
Copyright © Carrier Corp.
Accessory Sections• Filters• Access & Plenum• Mixing Box• Exhaust and Economizer Box• Humidifier• UV-C Germicidal Lights
Section 7 – Unit Accessories
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• Most common.
• Minimum filtration capability
• Up to MERV 13
• Throw-away:– Cardboard frames (shown)– Pleated media available
• Permanent– Cleanable– OSA intake hoods
Panel Filters
Section 7 – Unit Accessories
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Panel filters arranged in a “V” bank
• Reduced velocity through filters– Better filtration efficiency– Lower pressure drop vs. high velocity (flat)
filter section
Angle Filters
Section 7 – Unit Accessories
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• Medium to high efficiency
• Up to MERV 15
• Removes “fine” dust particles
• Greater filter area– Lower velocities– More dirt absorption
• Use with pre-filters
Bag Filters
Section 7 – Unit Accessories
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Box or Cartridge – MERV 15Box filters will not sag at reduced cfms in VAV systems.
Section 7 – Unit Accessories
Up to 95% Eff.
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HEPA / ULPA FilterHigh Efficiency Particulate Air
Both types are high efficiency (above 99%).
RigidRigidFrame
Ultra Low Penetration Air
Section 7 – Unit Accessories
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• Service access• Field-installed components
– Humidifiers– Sound attenuators– Controls, VFD.– UVC Lights
• Discharge Plenums– Provide duct outlet for
blow thru units
Blow-thru plenum with safety grate
Access and Plenum SectionsProvide space between components
Section 7 – Unit Accessories
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• Plenum with two air inlets– Outdoor air– Return air
• Provides– Ventilation air– Free cooling (economizer)– Indoor air quality (CO2)
Mixing Box
Section 7 – Unit Accessories
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Exhaust and Economizer Box
• Used downstream of return fan• Provides outlet to relieve excess air from building• Maintains space pressurization• Dampers are controlled by space pressure
sensor, or linked to mixing box dampers
Exhaust Box Mixing Box
ECONOMIZERSECTION
Section 7 – Unit Accessories
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Spray
Steam Grid
Atomizing
Humidifiers
Section 7 – Unit Accessories
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• According to BOMA(Building Owners & Managers Assoc.),the average condensate drain pan is cleanedonly 3.5 times per year
• Condensate drain pan and evaporator coilmay be sources of mold/bacteria growthunder certain conditions (68 to 86° F)
• Limits biological growth onevaporator coil and condensatedrain pan
– Maintains design air pressure drop– Helps reduce maintenance costs
• General rule of thumb sizing:– 1 lamp per 12 ft2 of coil surface
@ 12” distance from coil
UV-c Germicidal Lamps
Section 7 – Unit Accessories
Copyright © Carrier Corp.
Copyright © Carrier Corp.
Motor / System Controls
• Motor disconnects, starters, VFDs offered as options
• DDC control systems and components offered
• Factory installation– Reduces field labor costs– Minimizes mistakes and setup time
Section 7 – Unit Accessories
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Additional Configurations
CENTRAL STATION AIRHANDLERS
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Dual-Duct Unit• Blow-thru arrangement• Normally a constant volume system• Coil section with cooling and heating coils in parallel
– Coils referred to as “cold “ and “hot” decks, respectively– Provide simultaneous cooling and heating– Separate cooling and heating supply air ducts throughout building– Zone mixing boxes blend air from both ducts to meet space requirements
Section 8 – Additional Configurations
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Constant Volume, Blow-thru variation of Dual Duct System• Zoning dampers mounted on dual coil section in lieu of zone mixing boxes
– Opposed dampers mix air from cold and hot decks into a common duct– Dampers controlled by space temperature– Separate supply air ducts to each zone
Multizone Damper Arrangement
Section 8 – Additional Configurations
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Multizone variation• Adds a third “neutral” deck
between cold and hot decks– Neutral air is unconditioned return/outdoor air
Zoning dampers• Opposed Dampers can mix cold, hot,
and neutral air to meet zone needs• Minimizes reheat (mixing of cooled and heated air)
Triple-Deck Multizone
Section 8 – Additional Configurations
Copyright © Carrier Corp.
• Identified different types of air handlers
• Categorized air handler construction methods
• Identified air handler components
• Compared the difference between indoorand outdoor units
• Identified coil types
• Discussed the types of fans used
• Identified typical unit accessory sectionsand specified their use
Summary
Section 10 – Summary
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Summary
Copyright © Carrier Corp.
Work Session
Work Session
CENTRAL STATION AIR HANDLERS
Work SessionQuestions may have more than one correct answer. Include all correct answers in your re-
sponse to the questions below.
1. List the seven functions of a central station air handler as defined by ARI.
______________________ ______________________
______________________ ______________________
______________________ ______________________
______________________
2. True or False? A packaged air handler offers a wider size range with more features andflexibility than a central station air handler. ___________________
3. The size of a central station air handler is usually based on _______
the unit.
Copyright © Carrier Corp.
Technical Development Program
TDP-611 Central Station Air HandlersArtwork from Symbol Library used by permission ofSoftware Toolboxwww.softwaretoolbox.com/symbols