General; Conventions Used In This Manual - United Technologies Carrier Weathermaker 48A2 Controls, Start-Up, Operation, Service, And Troubleshooting

WARNING
DO NOT USE TORCH to remove any component. System
contains oil and refrigerant under pressure.
To remove a component, wear protective gloves and gog-
gles and proceed as follows:
a. Shut off electrical power to unit.
b. Recover refrigerant to relieve all pressure from sys-
tem using both high-pressure and low pressure ports.
c. Traces of vapor should be displaced with nitrogen
and the work area should be well ventilated. Refrig-
erant in contact with an open flame produces toxic
gases.
d. Cut component connection tubing with tubing cutter
and remove component from unit. Use a pan to catch
any oil that may come out of the lines and as a gage
for how much oil to add to the system.
e. Carefully unsweat remaining tubing stubs when nec-
essary. Oil can ignite when exposed to torch flame.
Failure to follow these procedures may result in personal
injury or death.
CAUTION
DO NOT re-use compressor oil or any oil that has been
exposed to the atmosphere. Dispose of oil per local codes
and regulations. DO NOT leave refrigerant system open to
air any longer than the actual time required to service the
equipment. Seal circuits being serviced and charge with
dry nitrogen to prevent oil contamination when timely
repairs cannot be completed. Failure to follow these proce-
dures may result in damage to equipment.

GENERAL

This book contains Controls, Start-Up, Operation, Service
and Troubleshooting information for the 48/50A Series
rooftop units. See Table 1. These units are equipped with
ComfortLink controls.
Use this guide in conjunction with the separate installation
instructions packaged with the unit. Refer to the Wiring Dia-
grams literature for more detailed wiring information.
Table 1 — A Series Product Line
UNIT
48A2 CV Unit with Gas Heat, Vertical Supply with MCHX Coil
48A3 VAV Unit with Gas Heat, Vertical Supply with MCHX Coil
48A4 CV Unit with Gas Heat, Horizontal Supply with MCHX Coil
48A5 VAV Unit with Gas Heat, Horizontal Supply with MCHX Coil
CV Unit with Optional Electric Heat, Vertical Supply with MCHX
50A2
Coil
VAV Unit with Optional Electric Heat, Vertical Supply with MCHX
50A3
Coil
CV Unit with Optional Electric Heat, Horizontal Supply with
50A4
MCHX Coil
VAV Unit with Optional Electric Heat, Horizontal Supply with
50A5
MCHX Coil
LEGEND
CV — Constant Volume
MCHX — Microchannel Heat Exchanger
VAV — Variable Air Volume
The A Series units provide ventilation, cooling, and heating
(when equipped) in variable air volume (VAV), variable volume
and temperature (VVT ® ), and constant volume (CV) applica-
tions. The A Series units contain the factory-installed Com-
fortLink control system which provides full system manage-
ment. The main base board (MBB) stores hundreds of unit
APPLICATION
configuration settings and 8 time of day schedules. The MBB
also performs self diagnostic tests at unit start-up, monitors the
operation of the unit, and provides alarms and alert information.
The system also contains other optional boards that are con-
nected to the MBB through the Local Equipment Network
(LEN). Information on system operation and status are sent to
the MBB processor by various sensors and optional boards that
are located at the unit. Access to the unit controls for configura-
tion, setpoint selection, schedule creation, and service can be
done through a unit-mounted scrolling marquee. Access can
also be done through the Carrier Comfort Network
system using the ComfortVIEW™ software, the accessory
Navigator™ hand-held display, or the System Pilot™ interface.
The ComfortLink system controls all aspects of the rooftop.
It controls the supply-fan motor, compressors, and economiz-
ers to maintain the proper temperature conditions. The controls
also cycle condenser fans to maintain suitable head pressure.
All VAV units are equipped with a standard VFD (variable fre-
quency drive) for supply fan speed control and supply duct
pressure control. The ComfortLink controls adjust the speed of
the VFD based on a static pressure sensor input. Constant vol-
ume (CV) units can be equipped with optional VFD for staged
air volume (SAV™) control. The indoor fan will operate at low
speed for energy savings and high speed when required. In ad-
dition, the ComfortLink controls can raise or lower the building
pressure using multiple power exhaust fans controlled from
economizer damper position or from a building pressure sen-
sor. The control safeties are continuously monitored to ensure
safe operation under all conditions. Sensors include suction
pressure transducers, discharge pressure transducers, and satu-
rated condensing temperature sensors which allow for display
of operational pressures and saturation temperatures.
A scheduling function, programmed by the user, controls
the unit occupied/unoccupied schedule. Up to 8 different
schedules can be programmed.
The controls also allow the service person to operate a quick
test so that all the controlled components can be checked for
proper operation.
Conventions Used in This Manual —
ing conventions for discussing configuration points for the lo-
cal display (scrolling marquee or Navigator accessory) will be
used in this manual.
Point names will be written with the Mode name first, then
any sub-modes, then the point name, each separated by an
arrow symbol (). Names will also be shown in bold and
italics. As an example, the IAQ Economizer Override Position
which is located in the Configuration mode, Indoor Air Quality
Configuration sub-mode, and the Air Quality Setpoints sub-
sub-mode, would be written as Configuration

IAQ.SP IQ.O.P. A list of point names can be found in
Appendix A.
This path name will show the user how to navigate through
the local display to reach the desired configuration. The user
would scroll through the modes and sub-modes using the
and keys. The arrow symbol in the path name rep-
resents pressing
ENTER
menu structure.
When a value is included as part of the path name, it will be
shown at the end of the path name after an equals sign. If the
value represents a configuration setting, an explanation will be
shown in parentheses after the value. As an example, Configu-
 
ration IAQ AQ.CF
ESCAPE
Pressing the
at any time will display an expanded text description of the four-
character point name. The expanded description is shown in the
local display tables (Appendix A).
3
The follow-
to move into the next level of the

IQ.AC = 1 (IAQ Analog Input).
and keys simultaneously
ENTER
(CCN)
®
 
IAQ