Specifications

85
Alert Code 423 (Y and W Simultaneously)
— This alert oc-
curs in Thermostat Mode when Y1 or Y2 is energized simulta-
neously with W1 or W2. Verify thermostat and thermostat
wiring. The software will enter either the cooling or heating
mode depending upon which input turned on first. This alert
resets automatically when Y1 and Y2 are not on simultaneous-
ly with W1 and W2.
Alert Codes 500, 501, 502, 503 (Current Sensor Failure)
—
Alert codes 500, 501, 502, and 503 are for compressors A1,
A2, B1, and B2 respectively. These alerts occur when the out-
put of the current sensor (CS) is a constant high value. These
alerts reset automatically. If the problem cannot be resolved
and the CS board must be replaced, the CS board can be
temporarily disabled while securing a replaced board. A CS
board is disabled by setting Configuration
→ COOL → CS.A1,
CS.A2, CS.B1 or CS.B2 to Disable.
If the current sensor board malfunctions or is not properly
connected to its assigned digital input, an alert will be generat-
ed. It takes 2 to 4 seconds to log the alert. If the alert is logged,
it stays for a minimum of 15 seconds to provide the application
a reasonable time to catch the failure. Compressors will be not
be inhibited by this failure. Recovery is automatic. Reason for
failure may be a faulty current sensor board, incorrect wiring,
or a damaged input on the MBB control board.
Alarm Code 700 (Supply Air Temperature Sensor Failure)
—
If the EDT sensor has been relocated after the heating section
then this alarm will indicate a failure of this sensor. This alarm
occurs when the Supply Air temperature sensor (Te mp era-
tures
→ AIR.T → SAT) is outside the range –40 to 240 F (–40 to
116 C). This alarm resets automatically. The cause of the alarm
is usually a faulty thermistor, a shorted or open thermistor
caused by a wiring error, or a loose connection.
Alert Codes 701 (Staged Gas 1 Thermistor Failure)
702 (Staged Gas 2 Thermistor Failure)
703 (Staged Gas 3 Thermistor Failure) — If any of the
staged gas thermistors (Temperatures → AIR.T → S.G.L1-3)
fails, an alert will be generated and the remaining thermistors
will be averaged together (Temperatures
→ AIR.T → S.G.LS)
without the failed thermistor. Recovery is automatic. Reason
for failure may be incorrect wiring, faulty thermistor, or a dam-
aged input on the staged gas control board (SCB).
A704 (Staged Gas Leaving Air Temperature Sum Total Fail-
ure) — If all three staged gas thermistors (Te mp era -
tures → AIR.T → S.G.L1-3) fail (the sensor is outside the range
of –40 F to 240 F), staged gas will be shut down and this alarm
will be generated. Recovery is automatic. Reason for failure
may be faulty wiring, faulty thermistors, or damaged inputs on
the staged gas control board (SCB).
Alert Code 705 (Limit Switch Thermistor Failure)
—Afail-
ure (the sensor is outside the range of –40 F to 240 F) of this
thermistor (Temperatures → AIR.T → S.G.LM) will cause an
alert to occur and a disabling of the limit switch monitoring
function for the staged gas control board (SCB). Recovery is
automatic. Reason for failure may be due to faulty wiring, a
faulty thermistor, or a damaged input on the staged gas control
board (SCB).
MAJOR SYSTEM COMPONENTS
General —
The 48/50A series package rooftop units with
electric cooling and with gas heating (48A units) or electric
cooling and electric heating (50A units) contain the
ComfortLink™ electronic control system that monitors all
operations of the rooftop. The control system is composed of
several components as listed below. See Fig. 13-19 for typical
control and power component schematics. Figures 20 and 21
show the layout of the control box, unit, and thermistor and
transducer locations.
Factory-Installed Components
MAIN BASE BOARD (MBB) — See Fig 22. The MBB is
the center of the ComfortLink control system. The MBB con-
tains the major portion of the operating software and controls
the operation of the unit. The MBB has 22 inputs and 11 out-
puts. See Table 93 for the inputs and output assignments. The
MBB also continuously monitors additional data from the
optional ECB1, ECB2, SCB, and CEM boards through the
LEN communications port. The MBB also interfaces with the
Carrier Comfort Network through the CCN communications
port. The board is located in the main control box.
ECONOMIZER BOARD (ECB1) — The ECB1 controls the
economizer actuator and the power exhaust fans. The ECB1
operates the economizer motor using a digital communication
signal that also provides status and diagnostics for the econo-
mizer motor. See Fig. 23. The ECB1 also controls the operation
of the power exhaust motors and provides up to 6 stages of dig-
itally sequenced power exhaust either based on the economizer
motor position or the building pressure. The board has 4 inputs
and 6 outputs. Details can be found in Table 94. The ECB1
board is located in an auxiliary box located at the end of the
unit behind the filter access door. The board also contains
a second LEN port than can be used with the accessory
Navigator™ display.
VAV BOARD (ECB2) — The VAV board (which is the same
hardware as the ECB1) is used to control the supply fan on
VAV units. See Fig. 23. It sends a 4 to 20 mA signal to the VFD
based on a supply duct pressure sensor connected to the board.
The board also accepts a signal from another pressure sensor
that monitors building pressure and controls the operation of
the optional modulating power exhaust motors. The board will
also be used on CV units with the optional building pressure
control feature and modulating power exhaust. This board is
also used to control a digitally controlled hot gas bypass sole-
noid with an integral orifice for use in low load applications.
This board is located in the auxiliary control box. Input and
output assignments are summarized in Table 95.
STAGED GAS HEAT BOARD (SCB) — When optional
staged gas heat is used on CV and VAV units, the SCB board is
installed and controls operation of the gas valves. See Fig. 24.
The SCB also provides additional sensors for monitoring of the
supply-air temperature. This board is located in the gas heat
section of the unit. The inputs and outputs are summarized in
Table 96.
CONTROL EXPANSION MODULE (CEM) — The optional
CEM (also available as an accessory) is used to accept inputs
for additional sensors or control sequence switches, including:
• smoke control mode field switches
• VAV Supply Air Temperature Set Point reset using an exter-
nal 4 to 20 mA signal
• outdoor air CO
2
sensor (for supply duct pressure reset using
an eternal 4 to 20 mA signal)
• external fan status pressure switch input (CV units)
• demand limit sequence proportional signal or discrete
switches
The CEM board is located in the main control box. See
Fig. 25. The inputs and outputs are summarized in Table 97.
INTEGRATED GAS CONTROL (IGC) — One IGC is pro-
vided with each bank of gas heat exchangers (2 used on the size
020-050 units and 3 on the size 060 unit). The IGC controls the
direct spark ignition system and monitors the rollout switch,
limit switches, and induced-draft motor Hall Effect switch. The
IGC is equipped with an LED (light-emitting diode) for diag-
nostics. See Table 98.
COMPRESSOR PROTECTION BOARD (CS) — This board
monitors the status of the compressor by sensing the current
flow to the compressors and then provides digital status signal
to the MBB.