Aaon LF-004 Installation Manual
LF Series
Air-Cooled Condenser Chillers
If the information in this manual is not
followed exactly, a fire or explosion
may result causing property damage,
personal injury or loss of life.
FOR YOUR SAFETY
Do not store or use gasoline or other
flammable vapors and liquids in the
vicinity of this or any other appliance.
QUALIFIED INSTALLER
Improper installation, adjustment,
alteration, service or maintenance
can cause property damage,
personal injury or loss of life.
Installation and service must be
performed by a Factory Trained
Service Technician. A copy of this
IOM should be kept with the unit.
Installation, Operation,
& Maintenance
Table of Contents
AAON LF Series Features and Options Introduction ..................................................................... 6
Safety .............................................................................................................................................. 7
LF Series Feature String Nomenclature .......................................................................................... 9
General Description ...................................................................................................................... 14
Receiving Unit ........................................................................................................................... 14
Chiller ........................................................................................................................................ 15
Wiring Diagrams ....................................................................................................................... 16
General Maintenance ................................................................................................................. 16
Primary Pumping Package ........................................................................................................ 16
Glycol ........................................................................................................................................ 17
Compression Tank ..................................................................................................................... 17
Pressure Relief Valve ................................................................................................................ 17
Manual and Automatic Air Vent ............................................................................................... 17
Dual Pumps ............................................................................................................................... 17
Differential Pressure Gauge and Thermometers ....................................................................... 17
Pipe Insulation ........................................................................................................................... 18
Installation..................................................................................................................................... 18
Forklifting the Unit (4-17 and 22-24 ton) ................................................................................. 18
Lifting the Unit .......................................................................................................................... 18
Locating the Unit ....................................................................................................................... 20
Water Connection ...................................................................................................................... 20
Mounting Isolation .................................................................................................................... 21
Access Doors ............................................................................................................................. 21
Low Ambient Operation ............................................................................................................ 21
LAC Valve ............................................................................................................................. 22
Condenser Flooding ............................................................................................................... 22
Electrical .................................................................................................................................... 23
Startup ........................................................................................................................................... 24
Maintenance .................................................................................................................................. 25
General ...................................................................................................................................... 25
Compressors .............................................................................................................................. 25
Refrigerant Filter Driers ............................................................................................................ 25
Adjusting Refrigerant Charge ................................................................................................... 25
Lubrication ................................................................................................................................ 27
Service ....................................................................................................................................... 27
Warranties ................................................................................................................................. 28
Condenser Tube Inspection ....................................................................................................... 28
Pump Operation ......................................................................................................................... 28
Access Doors ............................................................................................................................. 28
Pump Bearings - Lubrication .................................................................................................... 28
Air Inlet ..................................................................................................................................... 28
Propeller Fans and Motors ........................................................................................................ 28
Recommended Annual Inspection ............................................................................................ 29
Mechanical Cleaning ................................................................................................................. 29
Air-Cooled Condenser ............................................................................................................... 29
3
E-Coated Coil Cleaning ............................................................................................................ 29
Recommended Coil Cleaner .................................................................................................. 30
Recommended Chloride Remover ......................................................................................... 30
Microchannel Coil Cleaning ..................................................................................................... 30
Replacement Parts ..................................................................................................................... 32
AAON - Longview Warranty, Service, and Parts Department ................................................. 32
Appendix - Water Piping Component Information ...................................................................... 33
Water Pressure Relief Valve ..................................................................................................... 33
Automatic Air Vent Valves ....................................................................................................... 33
Pumps: Installation and Operating Instructions ........................................................................ 34
Dual Pump Specific Information ............................................................................................... 39
Valve Operation ........................................................................................................................ 39
Suction Guides .......................................................................................................................... 44
Flo-Trex Combination Valve .................................................................................................... 45
LF Series Startup Form ................................................................................................................. 50
Maintenance Log .......................................................................................................................... 53
Literature Change History............................................................................................................. 54
V45070 · Rev. A · 150716
(ACP J00425)
4
Index of Tables and Figures
Tables:
Table 1 - 4-7 & 9 ton Service Clearances ..................................................................................... 20
Table 2 - 8 & 10-13 ton Service Clearances ................................................................................. 20
Table 3 - 14-17 & 22-24 ton Service Clearances .......................................................................... 20
Table 4 - 21 & 26-55 ton Service Clearances ............................................................................... 20
Table 5 - Condenser Flooding....................................................................................................... 22
Table 6 - Max Filter Drier Pressure Drops ................................................................................... 25
Table 7 - Acceptable Refrigeration Circuit Values ....................................................................... 26
Table 8 - R-410A Refrigerant Temperature-Pressure Chart ......................................................... 27
Figures:
Figure 1 - Pressure Relief Valve ................................................................................................... 17
Figure 2 - Forklifting an LF Series A, B and C Cabinet, 4-17 and 22-24 tons ............................. 18
Figure 3 - Lifting Details of a 4-17 and 22-24 ton Standard Unit ................................................ 19
Figure 4 - Lifting Details of a 21 and 26-55 ton Standard Unit .................................................... 19
Figure 5 - Piping Schematic of Example System using the LAC Valve ...................................... 22
5
AAON LF Series Features and Options Introduction
Energy Efficiency
• Staged or 10-100% Variable Capacity R-
410A Scroll Compressors
• High Efficiency Air-Cooled
Microchannel Condenser Coils
• VFD Controlled Pumping Packages
• VFD Controlled or ECM Driven
Condenser Fans
• Waterside Economizers
• Factory Installed EXVs
Outdoor Mechanical Room
• Chilled Water Applications up to 55 tons
• Isolated Controls and Compressor
Compartment
• Isolated Evaporator and Pumping
Package Compartment
• Factory Engineered Primary Pumping
Packages
• Brazed Plate or Shell and Tube
Evaporators
Safety
• Phase and Brownout Protection
• Single Point Non-Fused Disconnect
Power Switch
• Waterside Thermometer and Pressure
Gauge
Installation and Maintenance
• Double Wall Rigid Polyurethane Foam
Injected Panel Construction
• Access Doors with Full Length Stainless
Steel Piano Hinges
• Molded Lockable Handles
• Factory Installed Convenience Outlet
• Service Vestibule Heating
• Controls Diagnostics
• Touchscreen Computer Controls
Interface
• Liquid Line Sight Glass
• Compressor Isolation Valves
• Color-Coded Wiring Diagrams
System Integration
• Complete System with AAON Chilled
Water Air Handling Units
• BMS Connectivity
• Grooved End Water Piping Connections
• Custom Order Paint Options
Environmentally Friendly
• R-410A Refrigerant
Extended Life
• 5 Year Compressor Warranty
• Condenser Coil Guards
• 2,500 Hour Salt Spray Tested Exterior
Corrosion Protection
• 6,000 Hour Salt Spray Tested Polymer
E-Coated Condenser Coils
6
Attention should be paid to the following statements:
NOTE - Notes are intended to clarify the unit installation, operation and maintenance.
CAUTION - Caution statements are given to prevent actions that may result in
equipment damage, property damage, or personal injury.
WARNING - Warning statements are given to prevent actions that could result in
equipment damage, property damage, personal injury or death.
DANGER - Danger statements are given to prevent actions that will result in equipment
damage, property damage, severe personal injury or death.
ELECTRIC SHOCK, FIRE OR
Failure to follow safety warnings
exactly could result in dangerous
operation, serious injury, death or
Improper servicing could result in
dangerous operation, serious injury,
When servicing controls, label all
wires prior to disconnecting.
Verify proper operation after
servicing. Secure all doors with
FIRE, EXPLOSION OR CARBON
Failure to replace proper controls
could result in fire, explosion or
carbon monoxide poisoning. Failure
to follow safety warnings exactly
could result in serious injury, death or
property damage. Do not store or use
gasoline or other flammable vapors
and liquids in the vicinity of this
appliance.
Electric shock hazard. Shut off all
electrical power to the unit to avoid
shock hazard or injury from rotating
parts.
Safety
EXPLOSION HAZARD
MONOXIDE POISONING HAZARD
property damage.
death, or property damage.
Reconnect wires correctly.
key-lock or nut and bolt.
7
8
To prevent motor overheating
compressors must cycle off for a
To maintain the proper oil level
compressors must cycle on for a
The cycle rate must not exceed 6
starts per hour.
WARNING
Do not leave VFDs unattended in
hand mode or manual bypass.
Damage to personnel or equipment
can occur if left unattended. When in
hand mode or manual bypass mode
VFDs will not respond to controls or
alarms.
PVC (Polyvinyl Chloride) and CPVC
(Chlorinated Polyvinyl Chloride) are
vulnerable to attack by certain
chemicals. Polyolester (POE) oils
used with R-410A and other
refrigerants, even in trace amounts,
in a PVC or CPVC piping system will
result in stress cracking of the piping
and fittings and complete piping
system failure.
CAUTION
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME
minimum of 5 minutes.
2 MINUTE MINIMUM ON TIME
minimum of 2 minutes.
VARIABLE FREQUENCY DRIVES
1. Startup and service must be performed
by a Factory Trained Service
Technician.
2. The unit is for outdoor use only. See
General Information section for more
information.
3. READ THE ENTIRE INSTALLATION,
OPERATION AND MAINTENANCE
MANUAL. OTHER IMPORTANT
SAFETY PRECAUTIONS ARE
PROVIDED THROUGHOUT THIS
MANUAL.
4. Keep this manual and all literature
safeguarded near or on the unit.
LF Series Feature String Nomenclature
Model Options
:
Unit Feature Options
GEN
MJREV SIZE SERIES MNREV VLT A1
A2
A3
A4
A5 B1
B2
B3
B4 1 2
3A
3B
3C
3D 4A
4B
4C
4D 5A
5B
5C
5D 6 7
8A
8B
8C
LF A -
031
- D - 0 - 3 - D A C 0
E - 0 0 0
0
: C 0 - 0 0 0 0 - 0 0 0 0 - 0 0 0 0 - 0 0 - 0 0 0
0 - 0 E 0 0 - 0 0 C 0 0 - 0 A 0 0 0 - 0 0 0 0 0 - 0 0 0 0 0 0 - 0 0 0 0 0 - 0 0 D
B
9
10A
10B
10C
10D
11
12
13
14
15 16
17
18
19
20 21
22
23
24
25
26A
26B
26C
26D
26E
26F
27
28
29
30
31 32
33
34
35
LF Series Feature String Nomenclature
MODEL OPTIONS
SERIES AND GENERATION
LF
MAJOR REVISION
A
UNIT SIZE
004 = 4 ton Capacity
005 = 5 ton Capacity
007 = 7 ton Capacity
008 = 8 ton Capacity
009 = 9 ton Capacity
010 = 10 ton Capacity
011 = 11 ton Capacity
013 = 13 ton Capacity
014 = 14 ton Capacity
015 = 15 ton Capacity
017 = 17 ton Capacity
021 = 21 ton Capacity
022 = 22 ton Capacity
024 = 24 ton Capacity
026 = 26 ton Capacity
031 = 31 ton Capacity
042 = 42 ton Capacity
048 = 48 ton Capacity
055 = 55 ton Capacity
SERIES
A = 4-7 and 9 ton units
B = 8 and 10-13 ton unit
C = 14-17 and 22-24 ton units
D = 21 and 26-55 ton units
MINOR REVISION
0
VOLTAGE
2 = 230V/3Φ/60Hz
3 = 460V/3Φ/60Hz
4 = 575V/3Φ/60Hz
8 = 208V/3Φ/60Hz
A1: COMPRESSOR STYLE
A = R-410A Scroll Compressors
D = R-410A Variable Capacity Scroll Compressors
E = R-410A Tandem Scroll Compressors
G = R-410A Tandem Variable Capacity Scroll
Compressors
A2: CONDENSER STYLE
A = Air-Cooled Microchannel Condenser
A3: EVAPORATOR CONFIGURATION
A = Brazed Plate
B = Oversized Brazed Plate
A4: Coating
0 = Standard
E = Polymer E-Coated Condenser Coil
A5: Staging
0 = Staged On/Off Compressors
E = All Variable Capacity Compressors
G = Half Variable Capacity Compressors
B1: Blank
0 = Standard
B2: Blank
0 = Standard
B3: Blank
0 = Standard
B4: Blank
0 = Standard
9
LF Series Feature String Nomenclature
Model Options
:
Unit Feature Options
GEN
MJREV SIZE SERIES MNREV VLT A1
A2
A3
A4
A5 B1
B2
B3
B4 1 2
3A
3B
3C
3D 4A
4B
4C
4D 5A
5B
5C
5D 6 7
8A
8B
8C
LF A -
031 - D - 0 - 3 - D A C 0 E - 0 0 0 0 :
C 0 - 0 0
0
0
- 0 0 0 0 - 0 0 0 0 - 0 0 - 0 0 0
0 - 0 E 0 0 - 0 0 C 0 0 - 0 A 0 0 0 - 0 0 0 0 0 - 0 0 0 0 0 0 - 0 0 0 0 0 - 0 0 D
B
9
10A
10B
10C
10D
11
12
13
14
15 16
17
18
19
20 21
22
23
24
25
26A
26B
26C
26D
26E
26F
27
28
29
30
31 32
33
34
35
10
UNIT FEATURE OPTIONS
1: Unit Orientation
0 = Standard Access End Water Connections
2: Pumping Style
B = Const. Primary Pumping System Large Pipe Size
D = Var. Primary Pumping System Large Pipe Size
J = No Pumping Package - Piping to Connections at
Wall Cutouts
3A: Building Pump Configuration
0 = No Building Pumps
A = 1 Pump + High Eff Motor
B = 1 Dual Pump + High Eff Motors
D = 1 Pump + VFD + High Eff Motor
E = 1 Dual Pump + 2 VFD's + High Eff Motors
3B: Building Pump Series and RPM
0 = No Building Pumps
A = 4360 (1,200 nominal rpm)
B = 4360 (1,800 nominal rpm)
C = 4360 (3,600 nominal rpm)
D = 4380 (1,200 nominal rpm)
E = 4380 (1,800 nominal rpm)
F = 4380 (3,600 nominal rpm)
K = 4382 (1,200 nominal rpm)
L = 4382 (1,800 nominal rpm)
M = 4382 (3,600 nominal rpm)
3C: Pump Size
0 = No Building Pumps
A = 1.5B
B = 2B
C = 2D
D = 3D
E = 1.5x1.5x6
F = 2x2x6
G = 3x3x6
H = 4x4x6
J = 6x6x6
K = 1.5x1.5x8
L = 2x2x8
M = 3x3x8
N = 4x4x8
P = 5x5x8
Q = 6x6x8
R = 8x8x8
S = 2x2x10
T = 3x3x10
U = 4x4x10
V = 6x6x10
W = 8x8x10
Y = 4x4x11.5
Z = 5x5x11.5
1 = 6x6x11.5
2 = 8x8x11.5
3 = 4x4x13
4 = 6x6x13
5 = 8x8x13
LF Series Feature String Nomenclature
Model Options
:
Unit Feature Options
GEN
MJREV SIZE SERIES MNREV VLT A1
A2
A3
A4
A5 B1
B2
B3
B4 1 2
3A
3B
3C
3D 4A
4B
4C
4D 5A
5B
5C
5D 6 7
8A
8B
8C
LF A -
031 - D - 0 - 3 - D A C 0 E - 0 0 0 0 : C 0 - 0 0 0
0 - 0 0 0 0 - 0 0 0 0 - 0 0 - 0 0
0
0 - 0
E
0 0 - 0 0 C 0 0 - 0 A 0 0 0 - 0 0 0 0 0 - 0 0 0 0 0 0 - 0 0 0 0 0 - 0 0 D
B
9
10A
10B
10C
10D
11
12
13
14
15 16
17
18
19
20 21
22
23
24
25
26A
26B
26C
26D
26E
26F
27
28
29
30
31 32
33
34
35
3D: Building Pump Motor Size
0 = No Building Pumps
A = 0.5 hp
B = 0.75 hp
C = 1 hp
D = 1.5 hp
E = 2 hp
F = 3 hp
G = 5 hp
H = 7.5 hp
J = 10 hp
K = 15 hp
L = 20 hp
M = 25 hp
N = 30 hp
P = 40 hp
Q = 50 hp
R = 60 hp
S = 75 hp
4A: Blank
0 = Standard
4B: Blank
0 = Standard
4C: Blank
0 = Standard
4D: Blank
0 = Standard
5A: Blank
0 = Standard
5B: Blank
0 = Standard
5C: Blank
0 = Standard
5D: Blank
0 = Standard
6: Refrigeration Options
0 = None
A = Hot Gas Bypass Non-Variable Capacity
Compressor Circuits
B = Hot Gas Bypass - All Circuits
7: Refrigeration Accessories
0 = Standard
A = Sight Glass
B = Compressor Isolation Valves
C = Option A + B
D = 1 Circuit Low Ambient
E = Option A + D
F = Option B + D
G = Option A + B + D
H = 2 Circuits Low Ambient
J = Option A + H
K = Option B + H
L = Option A + B + H
8A: Unit Disconnect Type
0 = Standard Single Point Power Block
A = Single Point Power Non-fused Disconnect
8B: Disconnect 1 Size
0 = Power Block
N = 100 amps
R = 150 amps
V = 250 amps
Z = 400 amps
8C: Blank
0 = Standard
9: Accessories
0 = None
B = Phase & Brown Out Protection
E = Compressor Sound Blanket
M = Option B + E
10A: Unit Control Sequence
0 = Standard AAON Controls
10B: Unit Control Supplier
E = MCS Controls
11
LF Series Feature String Nomenclature
Model Options
:
Unit Feature Options
GEN
MJREV SIZE SERIES MNREV VLT A1
A2
A3
A4
A5 B1
B2
B3
B4 1 2
3A
3B
3C
3D 4A
4B
4C
4D 5A
5B
5C
5D 6 7
8A
8B
8C
LF A -
031 - D - 0 - 3 - D A C 0 E - 0 0 0 0 : C 0 - 0 0 0 0 - 0 0 0 0 - 0 0 0 0 - 0 0 - 0 0 0
0 - 0
E
0 0 - 0 0 C 0 0 - 0 A 0 0 0 - 0 0 0 0 0 - 0 0
0
0 0 0 - 0 0 0 0 0 - 0 0 D
B
9
10A
10B
10C
10D
11
12
13
14
15 16
17
18
19
20 21
22
23
24
25
26A
26B
26C
26D
26E
26F
27
28
29
30
31 32
33
34
35
12
10C: Control Supplier Options
0 = None
C = Modem
10D: BMS Connection & Diagnostics
0 = None
A = BACnet IP
B = BACnet MSTP
C = Modbus IP
D = Modbus RTU
E = LonTalk
H = No BMS Connection with Diagnostics
J = BACnet IP with Diagnostics
K = BACnet MSTP with Diagnostics
L = Modbus IP with Diagnostics
M = Modbus RTU with Diagnostics
N = LonTalk with Diagnostics
11: Blank
0 = Standard
12: Vestibule Accessories
0 = None
C = Vestibule Heating (Electric)
13: Maintenance Accessories
0 = None
A = 115VAC Convenience Outlet Factory Wired
B = 115VAC Convenience Outlet Field Wired
14: Blank
0 = Standard
15: Code Options
0 = Standard ETL U.S.A. Listing
A = Chicago Code
16: Shipping Splits
0 = One Piece Unit
17: Air-Cooled Condenser Accessories
0 = Standard
A = Cond Coil Guards
C = ECM Condenser Fan Head Pressure Control
E = VFD Condenser Fan Head Pressure Control
G = Option A + C
J = Option A + E
18: Blank
0 = Standard
19: Blank
0 = Standard
20: Blank
0 = Standard
21: Blank
0 = Standard
22: Blank
0 = Standard
23: Blank
0 = Standard
24: Chiller Accessories 1
0 = None
A = Glycol chiller
C = Thermometers & Pressure Gauges
G = Option A + C
25: Blank
0 = Standard
26A: Blank
0 = Standard
26B: Blank
0 = Standard
26C: Blank
0 = Standard
Model Options
:
Unit Feature Options
GEN
MJREV SIZE SERIES MNREV VLT A1
A2
A3
A4
A5 B1
B2
B3
B4 1 2
3A
3B
3C
3D 4A
4B
4C
4D 5A
5B
5C
5D 6 7
8A
8B
8C
LF A -
031 - D - 0 - 3 - D A C 0 E - 0 0 0 0 : C 0 - 0 0 0 0 - 0 0 0 0 - 0 0 0 0 - 0 0 - 0 0 0
0 - 0 E 0 0 - 0 0 C 0 0 - 0 A 0 0 0 - 0 0 0 0 0 - 0 0
0
0 0 0 - 0 0 0 0 0 - 0 0 D
B
9
10A
10B
10C
10D
11
12
13
14
15 16
17
18
19
20 21
22
23
24
25
26A
26B
26C
26D
26E
26F
27
28
29
30
31 32
33
34
35
26D: Blank
0 = Standard
26E: Blank
0 = Standard
26F: Blank
0 = Standard
27: Blank
0 = Standard
28: Blank
0 = Standard
29: Blank
0 = Standard
30: Blank
0 = Standard
31: Blank
0 = Standard
LF Series Feature String Nomenclature
32: Blank
0 = Standard
33: Warranty
0 = Standard Warranty
D = Compressor Warranty Years 2-5
34: Cabinet Material
0 = Standard - Double Wall + R-13 Foam Insulation
35: Paint & Special Pricing Authorizations
B = Premium AAON Gray Paint Exterior
E = Option B + Shrink Wrap
X = Special Pricing Authorization + Premium AAON
Gray Paint Exterior
1 = Option X + Shrink Wrap
13
14
Improper installation, adjustment,
alteration, service or maintenance
can cause property damage,
personal injury or loss of life.
Installation and service must be
performed by a Factory Trained
The Clean Air Act of 1990 bans the
intentional venting of refrigerant as of
July 1, 1992. Approved methods of
recovery, recycling, or reclaiming
Coils and sheet metal surfaces
present sharp edges and care must
be taken when working with
equipment.
BURNING FOAM INSULATION IS
TOXIC! Do not cut holes into any
foam insulated panels with any flame
producing cutter such as a plasma
Failure to observe the following
instructions will result in premature
failure of your system and possible
voiding of the warranty.
General Description
LF Series air-cooled condenser chillers are
complete self-contained liquid chilling units.
They are factory assembled, wired, charged
and run-tested. Primary pumping package is
available as an optional feature.
Service Technician.
System should be sized in accordance with
the American Society of Heating,
Refrigeration and Air Conditioning
Engineers Handbook.
Installation of LF Series units must conform
to the ICC standards of the International
Mechanical Code, the International Building
Code, and local building, plumbing and
waste water codes. All appliances must be
electrically grounded in accordance with
local codes, or in the absence of local codes,
the current National Electric Code,
ANSI/NFPA 70 or the current Canadian
Electrical Code CSA C22.1.
must be followed.
cutter or cutting torch.
Receiving Unit
When received, the unit should be checked
for damage that might have occurred in
transit. If damage is found it should be noted
on the carrier’s Freight Bill. A request for
inspection by carrier’s agent should be made
in writing at once. Nameplate should be
checked to ensure the correct model sizes
and voltages have been received to match
the job requirements.
To prevent motor overheating
compressors must cycle off for a
To maintain the proper oil level
compressors must cycle on for a
The cycle rate must not exceed 6
starts per hour.
WARNING
Units are equipped with compressor
crankcase heaters, which should be
energized at least 24 hours prior to
cooling operation, to clear any liquid
refrigerant from the compressors.
Rotation must be checked on all
MOTORS AND COMPRESSORS of
three phase units. All motors, to
include and not be limited to pump
motors and condenser fan motors,
should all be checked by a qualified
service technician at startup and any
wiring alteration should only be made
at the unit power connection.
Scroll compressors are directional
and will be damaged by operation in
the wrong direction. Low pressure
switches on compressors have been
disconnected after factory testing.
Rotation should be checked by a
qualified service technician at startup
using suction and discharge pressure
gauges and any wiring alteration
should only be made at the unit
power connection.
Chiller
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME
minimum of 5 minutes.
2 MINUTE MINIMUM ON TIME
minimum of 2 minutes.
Failure to observe the following instructions
will result in premature failure of your
system, and possible voiding of the
warranty.
Before unit operation, the main power
switch must be turned on for at least twenty
four hours for units with compressor
crankcase heaters. This will give the
crankcase heater time to clear any liquid
accumulation out of the compressor before it
is required to run.
CRANKCASE HEATER
OPERATION
Never cut off the main power supply to the
unit, except for complete shutdown. When
power is cut off from the unit, any
compressors using crankcase heaters cannot
prevent refrigerant migration. This means
the compressor will cool down, and liquid
refrigerant may accumulate in the
compressor. Since the compressor is
designed to pump refrigerant gas, damage
may occur when power is restored.
Always control the system from the control
panel, never at the main power supply
(except for emergency or for complete
shutdown of the system).
The standard compressors must be on a
minimum of 2 minutes and off for a
15
16
Some units may require field wired
connections. Refer to the wiring
diagrams contained within the unit to
identify any components or controls
requiring additional wiring in the field
before placing the unit into service.
All additional field wiring should be
performed by a Factory Trained
Service Technician.
CAUTION
minimum of 5 minutes. The cycle rate must
be no more than 6 starts per hour.
The variable capacity compressors must be
on a minimum of 3 minutes and off for a
minimum of 3 minutes. The cycle rate must
be no more than 10 starts per hour.
The chiller is furnished with a pressure
differential switch that is factory installed
between the chilled water supply and return
connections. This sensor must not be
bypassed since it provides a signal to the
unit controller that water flow is present in
the heat exchanger and the unit can operate
without the danger of freezing the liquid.
The compressor life will be seriously
shortened by reduced lubrication, and the
pumping of excessive amounts of liquid oil
and refrigerant.
Wiring Diagrams
A complete set of unit specific wiring
diagram in point-to-point form is laminated
in plastic and located inside the control
compartment door.
FIELD WIRED CONNECTIONS
General Maintenance
When the initial startup is made and on a
periodic schedule during operation, it is
necessary to perform routine service checks
on the performance of the chiller. This
includes reading and recording suction
pressures and checking for normal subcooling and superheat.
Primary Pumping Package
Primary pumping uses a single pump to
move water (or glycol) through the
evaporator and back to the building. This
pumping package provides the necessary
flow of water to the system. The pump is
activated whenever the chiller is given a run
signal.
Water enters the unit through the return
water piping, and then travels through an air
scoop to remove any air that is entrapped in
the water. Following this, the water flows
through a suction guide with strainer. The
end of the suction guide is removable for
strainer access. The strainer assembly is
composed of two parts, the operational
strainer, and the startup strainer, (located
inside the operational strainer) which is to
be removed 24 hours after startup.
The pump is installed after the suction
guide, and before a combination valve (FloTrex). This combination valve acts as
isolation valve, check valve, and flow
balancing valve. The shell and tube or
brazed plate evaporator, is placed after the
combination valve in the water circuit, with
a differential pressure switch installed across
its inlet and outlet. This pressure switch
closes when the differential pressure
increases above the set-point, which should
be set 1-2 psig below the pressure drop
across the heat exchanger at design flow
rate. The closing differential pressure switch
signals the control system to indicate flow
through the heat exchanger and allow
cooling to activate as required to maintain
the setpoint. The water exiting the shell and
tube or brazed plate evaporator, leaves the
unit through the water out connection.
Glycol
Glycol units require a glycol feeder field
installed to replace fluid that is lost in the
system. Water should not be directly added
to glycol applications as this would dilute
the glycol concentration and thereby
increase the freezing temperature of the
fluid.
Compression Tank
As the water temperature in the system
increases, the volume that water displaces
increases. In order to compensate for these
forces, AAON recommends a prepressurized diaphragm compression tank
that is preset for 12 psig.
Pressure Relief Valve
Required pressure relief valve is installed in
the unit. This valve is set at 125 psig. Figure
1 shows inlet pressure versus capacity for
this pressure relief valve. See appendix for
additional information.
Figure 1 - Pressure Relief Valve
Manual and Automatic Air Vent
A manual air vent is supplied in chillers
without pumping packages. With a pumping
package option, there is an air scoop
installed at the high point of the system.
The air vent valve must be in the proper
position for operation. Ensure that the small
vent cap on the automatic air vent is
loosened one to two turns from the closed
position, allowing air to be vented from the
system. It is advisable to leave the cap on to
prevent impurities from entering the valve.
See appendix for additional information.
Dual Pumps
When redundant pumping is required, a
factory installed dualArm pump can be
ordered on units 15 tons and larger. A
dualArm pump is a pump with two
independent motors and pumps in a single
casing. This pump has a swing split-flapper
valve in the discharge port to prevent liquid
recirculation when only one pump is
operating. Isolation valves in the casing
allow one pump to be isolated and removed
for service while the other pump is still
operating.
The controls package will activate the pump
when the unit is given a run command. If the
controls do not recognize flow in 60
seconds, the second pump will be activated
and an alarm signal will be generated. If the
second pump does not activate, the cooling
will be locked out.
Differential Pressure Gauge and Thermometers
A differential pressure gauge and
thermometers are available as a factory
installed option when using a factory
installed pumping package. Thermometers
are installed around the evaporator of the
unit. A differential pressure gauge is
installed at each pump. This pressure gauge
is connected in three places to the water
piping: before the suction guide/strainer,
after the suction guide and before the pump,
and after the pump. There is also a needle
valve at each of these points to isolate the
pressure. To measure the pressure at any
given point, open the needle valve at that
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