Aaon CC-002 Installation Manual
CC SERIES
Condensers & Condensing Units
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.
WARNING
FOR YOUR SAFETY
Do not store or use gasoline or other
flammable vapors and liquids in the
vicinity of this or any other appliance.
WARNING
QUALIFIED INSTALLER
Improper installation, adjustment,
alteration, service or maintenance
can cause property damage,
personal injury or loss of life. Startup
and service must be performed by a
Factory Trained Service Technician.
A copy of this IOM should be kept
with the unit.
WARNING
Installation, Operation
& Maintenance
Table of Contents
Safety .............................................................................................................................................. 5
General Description ...................................................................................................................... 10
Receiving Unit .............................................................................................................................. 10
Storage .......................................................................................................................................... 10
Direct Expansion (DX) Condensing Units ................................................................................... 11
Wiring Diagrams ........................................................................................................................... 11
Installation..................................................................................................................................... 12
Locating Unit ................................................................................................................................ 12
Forklifting the Unit ....................................................................................................................... 13
Lifting the Unit ............................................................................................................................. 13
Electrical ....................................................................................................................................... 13
Thermostat .................................................................................................................................... 15
Refrigerant Piping ......................................................................................................................... 15
Determining Refrigerant Line Size ....................................................................................... 16
Liquid Line ............................................................................................................................ 16
Suction Line .......................................................................................................................... 17
Hot Gas Bypass Line ............................................................................................................ 18
Hot Gas Reheat ..................................................................................................................... 19
Predetermined Line Sizes ..................................................................................................... 19
Startup ........................................................................................................................................... 23
Compressors .................................................................................................................................. 23
Charging Refrigerant & Adjusting Refrigerant Charge ................................................................ 23
Before Charging .................................................................................................................... 23
Checking Liquid Sub-Cooling .............................................................................................. 24
Adjusting Sub-Cooling and Superheat Temperatures ........................................................... 24
Operation....................................................................................................................................... 27
Thermostat Operation ................................................................................................................... 27
Compressor Operation .................................................................................................................. 27
Variable Capacity Compressor Controller .................................................................................... 27
Low Voltage Terminals ................................................................................................................ 28
High Voltage Terminals ................................................................................................................ 28
Low Ambient Options................................................................................................................... 30
Maintenance .................................................................................................................................. 30
Coils .............................................................................................................................................. 30
E-Coated Coil Cleaning ................................................................................................................ 30
DX Cooling ................................................................................................................................... 32
Condenser Fan Motor Lubrication ................................................................................................ 32
Replacement Parts ......................................................................................................................... 32
AAON - Longview ....................................................................................................................... 32
Warranty, Service, and Parts Department ..................................................................................... 32
Refrigerant Piping Diagrams ........................................................................................................ 33
CC Series Startup Form ................................................................................................................ 45
Literature Change History............................................................................................................. 49
3
Index of Tables and Figures
Tables:
Table 1 - CC Series Clearances .................................................................................................... 12
Table 2- Recommended Elevation Minimums ............................................................................. 13
Table 3 - Predetermined Line Sizes for R-410A CC Condensing Units ...................................... 22
Table 4 - Sub-cooling and Superheat ............................................................................................ 24
Table 5 - R-410A Refrigerant Temperature-Pressure Chart ......................................................... 26
Table 6 - Demand Signal vs. Compressor Capacity Modulation .................................................. 28
Table 7 - Thermistor Temperature vs. Resistance Values ............................................................ 29
Figures:
Figure 1 - Vertical Air Discharge ................................................................................................. 12
Figure 2 - Horizontal Air Discharge ............................................................................................. 12
Figure 3 - Riser height versus total equivalent line length ........................................................... 21
Figure 4 - Variable Capacity Compressor Controller ................................................................... 28
Figure 5 - Compressor Controller Flash Code Details.................................................................. 29
Figure 6 - A/C only piping, AHU above CU ................................................................................ 33
Figure 7 - A/C only piping, AHU below CU ................................................................................ 34
Figure 8 - Modulating hot gas reheat piping, AHU above CU ..................................................... 35
Figure 9 - Modulating hot gas reheat piping, AHU below CU ..................................................... 36
Figure 10 - Hot gas bypass piping, AHU above CU .................................................................... 37
Figure 11 - Hot gas bypass piping, AHU below CU .................................................................... 38
Figure 12 - Modulating hot gas reheat with hot gas bypass piping, AHU above CU .................. 39
Figure 13 - Modulating hot gas reheat with hot gas bypass piping, AHU below CU .................. 40
Figure 14 - Heat pump piping, AHU above CU ........................................................................... 41
Figure 15 - Heat pump piping, AHU below CU ........................................................................... 42
Figure 16 - Heat pump with modulating hot gas reheat piping, AHU above CU ......................... 43
Figure 17 - Heat pump with modulating hot gas reheat, AHU below CU .................................... 44
R59081 · Rev. A · 140305
(ACP J00186)
4
Safety
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
EXPLOSION HAZARD
Failure to follow safety warnings
exactly could result in dangerous
operation, serious injury, death or
property damage.
Improper servicing could result in
dangerous operation, serious injury,
death or property damage.
Before servicing, disconnect all
electrical power to the unit. More
than one disconnect may be
provided.
When servicing controls, label all
wires prior to disconnecting.
Reconnect wires correctly.
Verify proper operation after
servicing. Secure all doors with
key-lock or nut and bolt.
WARNING
Electric shock hazard. Before
servicing, disconnect all electrical
power to the unit, including remote
disconnects, to avoid shock hazard
or injury from rotating parts. Follow
proper Lockout-Tagout procedures.
WARNING
FIRE, EXPLOSION OR CARBON
MONOXIDE POISONING HAZARD
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.
WARNING
5
GROUNDING REQUIRED
All field installed wiring must be
completed by qualified personnel.
Field installed wiring must comply
with NEC/CEC, local and state
electrical code requirements. Failure
to follow code requirements could
result in serious injury or death.
Provide proper unit ground in
accordance with these code
requirements.
WARNING
During installation, testing, servicing
and troubleshooting of the equipment
it may be necessary to work with live
electrical components. Only a
qualified licensed electrician or
individual properly trained in handling
live electrical components shall
perform these tasks.
Standard NFPA-70E, an OSHA
regulation requiring an Arc Flash
Boundary to be field established and
marked for identification of where
appropriate Personal Protective
Equipment (PPE) be worn, should be
followed.
WARNING
UNIT HANDLING
To prevent injury or death lifting
equipment capacity shall exceed unit
weight by an adequate safety factor.
Always test-lift unit not more than 24
inches high to verify proper center of
gravity lift point to avoid unit damage,
injury or death.
WARNING
ROTATING COMPONENTS
Unit contains fans with moving parts
that can cause serious injury. Do not
open door containing fans until the
power to the unit has been
disconnected and fan has stopped
rotating.
WARNING
Door compartments containing
hazardous voltage or rotating parts
are equipped with door latches to
allow locks. Door latches are shipped
with nut and bolts requiring tooled
access. If you do not replace the
shipping hardware with a pad lock
always re-install the nut & bolt after
closing the door.
CAUTION
Rotation must be checked on all
MOTORS AND COMPRESSORS of
3 phase units at startup by a qualified
service technician. Scroll
compressors are directional and can
be damaged if rotated in the wrong
direction. Compressor rotation must
be checked using suction and
discharge gauges. Fan motor rotation
should be checked for proper
operation. Alterations should only be
made at the unit power connection
CAUTION
6
Do not clean DX refrigerant coils with
hot water or steam. The use of hot
water or steam on refrigerant coils
will cause high pressure inside the
coil tubing and damage to the coil.
Some chemical coil cleaning
compounds are caustic or toxic. Use
these substances only in accordance
with the manufacturer’s usage
instructions. Failure to follow
instructions may result in equipment
damage, injury or death.
WARNING
To prevent damage to the unit, do not
use acidic chemical coil cleaners. Do
not use alkaline chemical coil
cleaners with a pH value greater than
8.5, after mixing, without first using
an aluminum corrosion inhibitor in the
cleaning solution.
CAUTION
CAUTION
Do not use oxygen, acetylene or air
in place of refrigerant and dry
nitrogen for leak testing. A violent
explosion may result causing injury or
death.
WARNING
Do not work in a closed area where
refrigerant or nitrogen gases may be
leaking. A sufficient quantity of
vapors may be present and cause
injury or death.
WARNING
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME
To prevent motor overheating
compressors must cycle off for a
minimum of 5 minutes.
5 MINUTE MINIMUM ON TIME
To maintain the proper oil level
compressors must cycle on for a
minimum of 5 minutes.
The cycle rate must not exceed 6
starts per hour.
WARNING
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
unit information.
3. Every unit has a unique equipment
nameplate with electrical, operational
and unit clearance specifications.
Always refer to the unit nameplate for
specific ratings unique to the model you
have purchased.
4. READ THE ENTIRE INSTALLATION,
OPERATION AND MAINTENANCE
MANUAL. OTHER IMPORTANT
SAFETY PRECAUTIONS ARE
PROVIDED THROUGHOUT THIS
MANUAL.
5. Keep this manual and all literature
safeguarded near or on the unit.
7
CC Series Feature String Nomenclature
Model Option
:
Unit Feature Options
GEN MJREV UNIT SIZE VOLTAGE
COMP TYPE
CIRCUITS 1 2 3 4 5 6 7
CC
- C -
010
- 3 - D - 2 : B D
0
0 0 A
0
BASE MODEL OPTIONS
Series and Generation
CC
Revision
C = Design Sequence
Unit Size
002 = 2 Ton Capacity - Horizontal Discharge
003 = 3 Ton Capacity - Horizontal Discharge
004 = 4 Ton Capacity - Horizontal Discharge
005 = 5 Ton Capacity - Horizontal Discharge
006 = 6 Ton Capacity
007 = 7 Ton Capacity
008 = 8 Ton Capacity
010 = 10 Ton Capacity
014 = 14 Ton Capacity
017 = 17 Ton Capacity
022 = 22 Ton Capacity
025 = 25 Ton Capacity
030 = 30 Ton Capacity
031 = 31 Ton Capacity
034 = 34 Ton Capacity
040 = 40 Ton Capacity
045 = 45 Ton Capacity
050 = 50 Ton Capacity
055 = 55 Ton Capacity
063 = 63 Ton Capacity
Voltage
1 = 230V/1Φ/60Hz
2 = 230V/3Φ/60Hz
3 = 460V/3Φ/60Hz
4 = 575V/3Φ/60Hz
8 = 208V/3Φ/60Hz
9 = 208V/1Φ/60Hz
Compressor Type
0 = No Compressor - Condenser Only
A = R-410A Single Step Scroll Compressor
B = R-410A Two Step Scroll Compressor
C = R-410A Tandem Scroll Compressors
D = R-410A Variable Capacity Scroll Compressor
9 = R-410A Variable Capacity Scroll Compressor Each Circuit
Number of Circuits
1 = One Circuit
2 = Two Circuits
4 = Four Circuits
UNIT FEATURE OPTIONS
Feature 1: Ambient Control
0 = Standard - 55°F Ambient
B = Adjustable Fan Cycling - 35°F Ambient
D = Modulating Fan Pressure Control - 35°F
Ambient
F = Flooded Condenser Low Ambient Controls +
Option B
G = Flooded Condenser Low Ambient Controls +
Option D
Feature 2: Refrigeration Options
0 = Standard - Split System Air Conditioner
A = External Hot Gas Bypass
B = Split System Heat Pump
D = Modulating Hot Gas Reheat
F = Options A + D
G = Options B + D
Feature 3: Controls
0 = Standard - Terminal Block with Control
Transformer
A = Suction Pressure Transducer
B = Phase and Brown Out Protection
C = Factory Wired 115V Outlet
D = Options A + B
E = Options A + C
F = Options B + C
G = Options A + B + C
J = Variable Capacity Compressor Integrated
Controls
8
CC Series Feature String Nomenclature
Model Option
:
Unit Feature Options
GEN MJREV UNIT SIZE VOLTAGE
COMP TYPE
CIRCUITS 1 2 3 4 5 6 7
CC
- C -
010
- 3 - D - 2 : B D
0
0 0 A
0
Feature 4: Coil Protection
0 = Standard,
A = Polymer E-Coated Coil
Feature 5: Cabinet Options
0 = Standard
B = Compressor Sound Blanket
D = Exterior Corrosion Protection
E = Options B + D
R = California OSHPD Certified
S = Shake Table Cert. (ASHE 7-05/ICC-ES AC 156)
T = Seismic Construction (Non-Certified)
U = Options D + R
W = Options D + S
Z = Options D + T
Feature 6: Warranty
0 = Standard
A = Second to Fifth Year Extended Compressor
Warranty
Feature 7: Type
0 = Standard
X = Special Price Authorization
9
Improper installation, adjustment,
alteration, service or maintenance
can cause property damage,
personal injury or loss of life. Startup
and service must be performed by a
Factory Trained Service Technician .
WARNING
Coils and sheet metal surfaces
present sharp edges and care must
be taken when working with
equipment.
WARNING
The Clean Air Act of 1990 bans the
intentional venting of refrigerant as of
July 1, 1992. Approved methods of
recovery, recycling, or reclaiming
must be followed.
CAUTION
Failure to observe the following
instructions will result in premature
failure of your system and possible
voiding of the warranty.
WARNING
General Description
AAON CC Series air-cooled condensers and
condensing units have been designed for
outdoor installation only. Startup and
service must be performed by a Factory
Trained Service Technician.
Codes and Ordinances
System should be sized in accordance with
the American Society of Heating,
Refrigeration and Air Conditioning
Engineers Handbook.
Installation of CC 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.
10
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.
The warranty card must be completed in full
and returned to AAON not more than 3
months after unit is delivered.
Storage
If installation will not occur immediately
following delivery, store equipment in a dry
protected area away from construction
traffic and in the proper orientation as
marked on the packaging with all internal
packaging in place. Secure all loose-shipped
items.
CRANKCASE HEATER
OPERATION
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.
CAUTION
Direct Expansion (DX) Condensing Units
Condensing units are factory assembled and
wired, including a holding charge of
refrigerant. Refrigeration systems include
factory provided liquid line filter driers and
fully hermetic scroll compressors with a
positive pressure forced lubrication system.
Never cut off the main power supply to the
unit, except for servicing, emergency, or
complete shutdown of the unit. When power
is cut off from the unit, compressors using
crankcase heaters cannot prevent refrigerant
migration. This means the compressor may
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.
If power to the unit must be off for more
than an hour, turn the thermostat system
switch to “Off”, or turn the unit off at the
control panel, and then cut off the main
power supply. Leave the unit off until the
main power supply has been turned on again
for at least 24 hours. This will give the
crankcase heater time to clear any liquid
accumulation out of the compressor before it
is required to run.
Always control the system from the
thermostat, or control panel, never at the
main power supply, except for servicing,
emergency, or complete shutdown of the
unit.
Note: Low Ambient Operation
Units without a low ambient option, such as
adjustable fan cycling or the 0°F low
ambient option, will not operate in the
cooling mode of operation properly when
the outdoor temperature is below 55°F. Low
ambient and/or air handling unit economizer
options are recommended if cooling
operation below 55°F is expected.
Note: Multiple Systems with Multiple
Thermostats
When several heating and cooling split
systems are used to condition a space all
thermostat switches must be set in either
heating mode, cooling mode or off. Do not
leave part of the systems switched to the
opposite mode. Cooling only systems should
be switched off at the thermostat during the
heating season.
Wiring Diagrams
Unit specific wiring diagrams are laminated
in plastic and affixed inside the controls
compartment door.
11
Location
Unit Size
2-5 tons
6-63 tons
Front
Unobstructed
48”
Back
12”
48”
Left Side
10”
36”
Right Side
36”
36”
Top
0”
Unobstructed
Front
Left Side
Right Side
Installation
AAON equipment has been designed for
quick and easy installation.
Locating Unit
CC Series units are designed for outdoor
application and placement at ground level or
on a rooftop. Units must be placed on a level
and solid foundation that can support the
unit’s weight.
When rooftop mounted, a steel frame must
be provided that will support the unit above
the roof itself for load distribution.
When installed at ground level, a one-piece
concrete slab - preferably at least 4 inches
thick - should be used with footings that
extend below the frost line (a substantial
base that will not settle). Slab should be
surrounded by a graveled area for proper
drainage and should not adjoin the building
as sound and vibration may be transmitted to
the structure. Care must also be taken to
protect the coils and fins from damage due
to vandalism or other hazards.
Table 1 - CC Series Clearances
Figure 1 - Vertical Air Discharge
CC Series Orientation
Figure 2 - Horizontal Air Discharge
CC Series Orientation
Air flow to and from the unit must not be
restricted. Coils and fans must be free of any
obstructions and debris in order to start and
operate properly with a correct amount of
airflow. Obstruction to airflow will result in
decreased performance and efficiency.
6-63 ton units are vertical air discharge and
should not be installed in an enclosure or pit
that is deeper than the height of the unit. If
recessed installation is necessary, the
clearance to maintain proper air flow is at
least 6 feet. There must be no obstruction
above the equipment. Do not place the unit
under an overhang.
12
Design
Temperature
Suggest Minimum
Elevation
+15 F and above
3”
-5 F to +17 F
8”
Below -5 F
12”
Incorrect lifting can cause damage to
the unit.
CAUTION
Electric shock hazard. Before
attempting to perform any installation,
service, or maintenance, shut off all
electrical power to the unit at the
disconnect switches. Unit may have
multiple power supplies. Failure to
disconnect power could result in
dangerous operation, serious injury,
death or property damage.
WARNING
2-5 ton units are horizontal discharge and
must have no obstruction on the discharge
side of the unit. Unit should not be installed
in an enclosure or pit.
Placement relative to the building or other
structures must be carefully selected.
Consider the effects of outdoor fan noise on
any adjacent occupied space. It is
recommended that the unit be placed so that
air does not discharge toward windows on
intakes less than 25 feet away.
Service compartments must be accessible
for periodic servicing of compressors,
controls, safety devices, refrigerant
service/shutoff valves, coils, and condenser
fans.
Heat pumps require special location
consideration in areas where snow
accumulation can become an obstruction
and areas with prolonged continuous
subfreezing temperatures. The unit must be
placed to permit free drainage of the defrost
water and ice. A minimum 3 inches
clearance under the outdoor coil is required
in the milder climates. In more severe
weather locations, it is recommended that
the unit include additional elevation to allow
unobstructed drainage and airflow.
Table 2- Recommended Elevation
Minimums
Forklifting the Unit
Units can be lifted from the base using a
forklift. This allows movement and
placement without causing physical damage.
Larger units may require a fork length of 72
inches or the fork must have 72 inch fork
extensions. Smaller units can be lifted from
multiple sides, while larger units must be
lifted from the front side.
Forks must be perpendicular to the unit and
they must be in far enough that the back of
the fork is no more than 6 inches away from
the edge of the unit.
Lifting the Unit
If cables or chains are used to hoist the unit
they must be the same length and care
should be taken to prevent damage to the
cabinet. Arrange spreader bars, blocking, or
other lifting devices to prevent any damage
to the cabinet, coils, and condenser fans.
Before lifting unit, be sure that all shipping
material has been removed from unit. Secure
hooks and cables at all lifting points/lugs
provided on the unit.
Electrical
Verify the unit nameplate agrees with power
supply. Connect power and control field
wiring as shown on the unit specific wiring
diagram provided laminated and attached to
the door in the controls compartment.
13
Rotation must be checked on all
MOTORS AND COMPRESSORS of
three phase units. Condenser fan
motors should be checked by a
qualified service technician at startup
and any wiring alteration should only
be made at the unit power
connection.
CAUTION
Three phase voltage imbalance will
cause motor overheating and
premature failure.
CAUTION
Route power and control wiring through the
utility entries on the sides of the unit. It is
recommended not to run power and control
signal wires in the same conduit. If the
control wires are run inside the same conduit
as the power wiring use 600 volt wire, or as
required by applicable codes.
Size supply conductors based on the unit
MCA rating. Supply conductors must be
rated a minimum of 75°C.
Protect the branch circuit in accordance with
code requirements. The unit 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.
Note: Units are factory wired for 208V,
230V, 460V or 575V. In some units, the
208V and 230V options may also be
provided in single or three phase
configurations. The transformer
configuration must be checked by a
qualified technician prior to startup.
Wire power leads to the unit terminal block
or compressor contactor. All wiring beyond
this point has been done by the manufacturer
and cannot be modified without effecting the
unit's agency/safety certification.
All units require field supplied electrical
overcurrent and short circuit protection.
Device must not be sized larger than the
Maximum Overcurrent Protection (MOP)
shown on the unit nameplate.
Codes may require a disconnect switch be
within sight of the unit.
It is recommended that the field installed
overcurrent protection or disconnect switch
not be installed on the unit.
14
Supply voltage must be within the min/max
range shown on the unit nameplate.
Available short circuit current should not
exceed the short circuit current rating
(SCCR) shown on the unit nameplate.
Three phase voltage imbalance will cause
motor overheating and premature failure.
The maximum allowable imbalance is 2.0%.
Voltage imbalance is defined as 100 times
the maximum deviation from the average
voltage divided by the average voltage.
Example:
(221V+230V+227V)/3 = 226V, then
100*(226V-221V)/226V = 2.2%, which
exceeds the allowable imbalance.
Check voltage imbalance at the unit
disconnect switch and at the compressor
terminal. Contact your local power company
for line voltage corrections.
Installing contractor must check for proper
motor rotation and check fan motor
amperage listed on the motor nameplate is
not exceeded.
Scroll compressors are directional
and will be damaged by operation in
the wrong direction. High 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.
CAUTION
This section is for information only
and is not intended to provide all
details required by the designer or
installer of the refrigerant piping
between the condenser or
condensing unit and the air handling
unit. AAON, Inc. is not responsible for
interconnecting refrigerant piping.
Consult ASHRAE Handbook –
Refrigeration and ASME Standards.
CAUTION
Wire control signals to the unit’s low
voltage terminal block located in the
controls compartment.
If any factory installed wiring must be
replaced, use a minimum 105°C type AWM
insulated conductors.
Thermostat
If a thermostat is used for unit control,
thermostat should be located on an inside
wall 4-5 feet above the floor where it will
not be subjected to drafts, sun exposure, or
heat from electrical fixtures or appliances.
Follow thermostat manufacturer’s
instructions for general installation
procedure.
Thermostat control wiring size must be large
enough to prevent excess voltage drop and
ensure proper operation.
All external devices must be powered via a
separate external power supply.
Refrigerant Piping
(See back of the manual for refrigerant
piping diagrams.)
General
Piping from the condensing unit to the air
handler is the responsibility of the installing
contractor.
Use only clean type “ACR” copper tubing
that has been joined with high temperature
brazing alloy.
The pipe or line sizes must be selected to
meet the actual installation conditions and
not simply based on the connection sizes at
the condensing unit or air handler.
All CC Series condensing units are provided
with in-line shutoff valves on both the liquid
and suction lines. These should remain
closed until the system is ready for start-up
after installation.
Piping should conform to generally accepted
practices and codes.
Care must be taken not to cross the circuits
on multiple circuit systems.
Upon completion of piping connection, the
interconnecting piping and air handler
MUST BE evacuated to 500 microns or less;
leak checked and charged with refrigerant.
15
Line sizes must be selected to meet
actual installation conditions, not
simply based on the connection sizes
at the condensing unit or air handling
unit.
CAUTION
Determining Refrigerant Line Size
The piping between the condenser and low
side must ensure:
1. Minimum pressure drop, and
2. Continuous oil return, and
3. Prevention of liquid refrigerant slugging,
or carryover
Minimizing the refrigerant line size is
favorable from an economic perspective,
reducing installation costs, and reducing the
potential for leakage. However, as pipe
diameters narrow, pressure-reducing
frictional forces increase.
Excessive suction line pressure drop causes
loss of compressor capacity and increased
power usage resulting in reduced system
efficiency. Excessive pressure drops in the
liquid line can cause the liquid refrigerant to
flash, resulting in faulty TXV operation and
improper system performance. In order to
operate efficiently and cost effectively,
while avoiding malfunction, refrigeration
systems must be designed to minimize both
cost and pressure loss.
Equivalent Line Length
All line lengths discussed in this manual,
unless specifically stated otherwise, are
Equivalent Line Lengths. The frictional
pressure drop through valves, fittings, and
accessories is determined by establishing the
equivalent length of straight pipe of the
same diameter. Always use equivalent line
16
lengths when calculating pressure drop.
Special piping provisions must be taken
when lines are run underground, up vertical
risers, or in excessively long line runs.
Liquid Line
When sizing the liquid line, it is important to
minimize the refrigerant charge to reduce
installation costs and improve system
reliability. This can be achieved by
minimizing the liquid line diameter.
However, reducing the pipe diameter will
increase the velocity of the liquid refrigerant
which increases the frictional pressure drop
in the liquid line, and causes other
undesirable effects such as noise.
Maintaining the pressure in the liquid line is
critical to ensuring sufficient saturation
temperature, avoiding flashing upstream of
the TXV, and maintaining system
efficiency. Pressure losses through the
liquid line due to frictional contact, installed
accessories, and vertical risers are
inevitable. Maintaining adequate subcooling at the condenser to overcome these
losses is the only method to ensure that
liquid refrigerant reaches the TXV.
Liquid refrigerant traveling upwards in a
riser loses head pressure. If the evaporator is
below the condenser, and the liquid line
does not include risers, the gravitational
force will increase the pressure of the liquid
refrigerant. This will allow the refrigerant to
withstand greater frictional losses without
the occurrence of flashing prior to the TXV.
A moisture-indicating sight glass may be
field installed in the liquid line to indicate
the occurrence of premature flashing or
moisture in the line. The sight glass should
not be used to determine if the system is
properly charged. Use temperature and
pressure measurements to determine
liquid sub-cooling, not the sight glass.
Loading...