Troubleshooting; Complete Unit Stoppage; Restart Procedure; Control Module Communication - Carrier 48PG03-16 Controls, Start-Up, Operation, Service And Troubleshooting Instructions

NOTE: An accessory filter switch can be used along with the
alarm relay output function to indicate dirty filter service need.
See the Troubleshooting section for more information on
viewing, diagnosing, and clearing alerts and alarms.

TROUBLESHOOTING

The Scrolling Marquee display shows the actual operating
conditions of the unit while it is running. If there are alarms or
there have been alarms, they will be displayed in either the
current alarm list or the history alarm list. (See Table 92.) The
Service Test mode allows proper operation of the compressors,
fans, and other components to be checked while the unit is not
operating. See Service Test.

Complete Unit Stoppage

There are several conditions that can cause the unit not to provide
heating or cooling:
S If an alarm is active which causes the unit to shut down,
diagnose the problem using the information provided
in Alarms and Alerts section below.
S Cooling and heating loads are satisfied.
Programmed occupancy schedule.
S
S General power failure.
Tripped CB1 or CB2 (24-volt transformer circuit
S
breakers).
S Unit is turned off through the CCN network.
S If supply-air temperature is less than the Minimum SAT
Lower Level (SAT.L) configuration value, unit cannot
cool.
S If outdoor-air temperature is less than the Compressor
Lockout Temperature (CA.LO, CB.LO, CC.LO)
configuration value, unit cannot cool.
S If outdoor-air temperature is greater than the Heating
Lockout Temperature (HT.LO) configuration value,
unit cannot heat.

Restart Procedure

Before attempting to restart the machine, check the alarm list to
determine the cause of the shut down. If the shutdown alarm for a
particular control function has occurred, determine and correct the
cause before allowing the unit to run under its own control again.
When there is problem, the unit should be diagnosed in Service
Test mode. The alarms must be reset before the control function
can operate in either Normal mode or Service Test mode.

Control Module Communication

Red LED
Proper operation of the MBB and ECB control boards can be
visually checked by looking at the red status LEDs. When
operating correctly, the red status LEDs should blink in unison at
a rate of once every 2 seconds. If the red LED on the ECB is not
blinking, check the DIP switch positions on the board. If the red
LEDs are not blinking in unison, verify that correct power is
being supplied to all modules. Also, be sure that the board is
supplied with the current software. If necessary, reload current
software. A board LED that is lit continuously or blinking at a
rate of once per second or faster indicates that the board should be
replaced.
Green LED
The MBB and ECB each have one green LED. The Local
Equipment Network (LEN) LED should always be blinking
whenever power is on. If LEN LED is not blinking, check LEN
connections for potential communication errors (J3 and J4
connectors). Communication between modules is accomplished
by a 3-wire sensor bus. These 3 wires run in parallel from module
to module. The J4 connector on the MBB also provides both
power and communication directly to the Scrolling Marquee
display.
Yellow LED
The MBB has one yellow LED which is used to indicate CCN
communication activity. The Carrier Comfort Network® (CCN)
LED will blink during times of network communication.

Alarms and Alerts

Viewing and Clearing Unit Alarms
Presence of active alarms will be indicated on the Scrolling
Marquee display by the Alarm Status light turning on and by the
number of active alarms being displayed in the automatic View of
Run Status. Presence of active alarms may also be signaled on the
Alarm Output terminals. Each alarm may also be broadcast on the
CCN network. Active alarms and past alarm history can be
reviewed and cleared via the local display or a CCN device. The
following menu locations are used for the local display:
Alarms→R.CURR (Reset All Current Alarms)
Change to YES to reset all active alarms. Turning unit power off
will also reset all current alarms.
Alarms→R.HIST (Reset Alarm History)
Change to YES to reset the alarm history. Turning unit power off
will not reset the alarm history.
Alarms→CURR (Currently Active Alarms)
Use the ENTER key, then scroll through any alarm numbers
using the up and down arrow keys. Alarms are displayed in
numerical order.
Alarms→HIST (Alarm History)
Use the ENTER key, then scroll through any alarm numbers
using the up and down arrow keys. Up to 20 alarms are displayed
in order of occurrence, with time and date.
The description for an alarm can be viewed on the Scrolling
Marquee display by pressing ESCAPE and ENTER keys
simultaneously while displaying the alarm code number. Be sure
to expand description for each code, because in some cases there
are different possible descriptions and causes for the same code
number.
Diagnostic Alarm Codes and Possible Causes
Alert Codes T051, T052, T055 and T059 (Compressor Safety)
Alert codes T051, T052, T055, and T059 are for compressors
A1, A2, B1, and C1, respectively. These alerts occur when the
Current Sensor (CS) does not detect compressor current during
compressor operation. When this occurs, the control turns off the
compressor and logs a strike for the respective circuit. These
alerts reset automatically.
The possible causes are:
1. High-pressure switch (HPS) open. The HPS is wired in
series with compressor relays on the MBB. If the
high-pressure switch opens during compressor operation,
the compressor stops, and the CS no longer detects
current, causing the control to activate this alert.
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