Carrier JK034-074 Air Conditioner User Manual


 
CONTENTS (cont)
Page
CODES 59 AND 60: LOW-PRESSURE SWITCH
CODES 63 AND 64: OIL PRESSURE SWITCH
CODE 70: ILLEGAL UNIT CONFIGURATION
CODES 71 TO 76: THERMISTOR/RESISTOR
FAILURE
CODE 81: RESET THERMISTOR OR
POTENTIOMETER FAILURE
CODE 82: LEAVING-AIR TEMPERATURE SET POINT
POTENTIOMETER FAILURE
CODE 83: ECONOMIZER FEEDBACK
POTENTIOMETER FAILURE
CODE 84: RESET LIMIT POTENTIOMETER
FAILURE
CODE 85: DEMAND LIMIT POTENTIOMETER (P4)
FAILURE
CODE 86: MINIMUM POSITION ECONOMIZER
POTENTIOMETER FAILURE
CODE 87: WARM-UP TEMPERATURE SET POINT
FAILURE
Thermistor Troubleshooting
....................47
Electronic Controls Checkout ..................47
PROCESSOR BOARD CHECKOUT
RELAY BOARD TROUBLESHOOTING
DISPLAY BOARD CHECKOUT
ACCESSORY BOARD CHECKOUT
TWO-STEP DEMAND LIMIT CONTROL MODULE
(DLCM) TROUBLESHOOTING
Enthalpy Sensor Checkout
.....................51
Economizer Motor ............................52
Variable Frequency Drive ......................52
STANDARD TRANSDUCER CONTROL
EXTERNAL SIGNAL CONTROL
SUPPLY FAN MOTOR OVERLOAD PROTECTION
VFD Operation
...............................54
VFD Operational Status ........................54
Restoring Factory VFD Defaults ................54
Unit Wiring ..................................54
START-UP CHECKLIST ..................CL-1, CL-2
SAFETY CONSIDERATIONS
Installing, starting up, and servicing this equipment can
be hazardous due to system pressures, electrical compo-
nents; and equipment location (roof, elevated structures, etc.).
Only trained, qualified installers and service mechanics should
install, start up, and service this equipment.
When working on this equipment, observe precautions in
the literature; on tags, stickers, and labels attached to the equip-
ment, and any other safety precautions that apply. Follow all
safety codes. Wear safety glasses and work gloves. Use care
in handling, rigging, and setting this equipment, and in han-
dling all electrical components.
Electrical shock can cause personal injury and death.
Shut off all power to this equipment during installation
and service. There may be more than one disconnect
switch. Tag all disconnect locations to alert others not
to restore power until work is completed.
This unit uses a microprocessor-based electronic con-
trol system. Do not use jumpers or other tools to short
out components, or to bypass or otherwise depart from
recommended procedures. Any short-to-ground of the
control board or accompanying wiring may destroy the
electronic modules or electrical components.
GENERAL
IMPORTANT: This literature contains controls,
operation, and troubleshooting data for 48FK,JK and
50FK,FY,JK,JY variable air volume rooftop units. Use
this guide in conjunction with the separate Installation
Instructions literature packaged with the unit.
Carrier 48FK,JK and 50FK,FY,JK,JY units provide ven-
tilation, cooling, and heating (when equipped) in Variable
Air Volume (VAV) applications. These units contain factory-
installed controls which provide full system management.
The unit controls also perform self diagnostic tests at unit
start-up, monitor operation of the unit, and provide alarms.
Information on system operation and status are sent to the
central processors by various sensors that are located at the
unit and in the conditioned space. Each unit is equipped with
a display board.
Rooftop Information The rooftop controls cycle
supply-fan motor, compressors, and unloaders to maintain
the proper temperature conditions. The controls also cycle
condenser fans to maintain suitable head pressure. Safeties
are continuously monitored to prevent the unit from oper-
ating under abnormal conditions. The controls provide con-
trol of economizer and cycle or control heating as required.
The controls also allow the service person to operate a
‘quick test’so that all the controlled components can be checked
for proper operation.
IMPORTANT: The field-supplied and installed switch
(or timeclock) MUST BE CLOSED to put unit into
the Occupied mode. Unit WILL NOT START until this
is accomplished. See base unit installation instructions
literature for details.
VAV Control System The 30 to 100-ton VAV roof-
top units contain a microprocessor-based electronic control
system that controls and monitors the rooftop unit functions.
The VAV control system is composed of severalcomponents:
processor board
relay board
display board
thermistors
compressor operation feedback (control relay)
accessory board
temperature reset package*
single-step demand limit*
two-step demand limit control module*
*Field-installed accessories.
The VAV control system monitors and controls the fol-
lowing functions of the rooftop unit:
supply-air temperature (unit capacity)
morning warm-up or electric heat (if equipped)
head pressure control, fan cycling
economizer position
diagnostic display
unit check-out (quick test)
supply air temperature reset (if equipped)
demand limiting (if equipped)
Processor Board The processor board, shown in
Fig. 1, contains the logic and the necessary hardware to drive
the outputs and the display board. The processor board is
enclosed by a sheet metal cover and a heater. The heater is
controlled by a thermostat to keep the processor temperature
above 32 F (0° C). All electrical connections are made to the
processor board through wire and ribbon cables.
2