Specifications

104
POWER EXHAUST — The units can be equipped with an
optional power exhaust system. The power exhaust fans are
forward-curved fans with direct-drive motors. The motors are
controlled directly by the ComfortLink™ control through the
ECB1 board. On the 20 to 50 ton units there are 4 fans. On the
60 ton units there are 6 fans. The fan sequences are controlled
to provide 4 stages on the 20 to 50 ton units and 6 stages
on the 60 ton unit. There are two control methods. For CV
applications the fans can be configured for 2 stages based on
adjustable economizer damper positions. For VAV applications
and CV units with the building pressure control option, the fans
are sequenced to maintain a building pressure set point based
on a building pressure transducer.
ECONOMIZER MOTOR — The economizer outside air and
return air dampers are gear-driven dampers without linkage. A
digitally controlled economizer motor controls their position.
The motor position is controlled by the ECB1 board by means
of a digital two-way communication signal. This allows for
accurate control of the motors as well as feedback information
and diagnostics information. The control has a self-calibration
routine that allows the motor position to be configured at initial
unit start-up. The motor is located on the economizer and can
be reached through the filter access door.
THERMISTORS AND PRESSURE TRANSDUCERS —
The unit is equipped with thermistors for measurement of
temperatures.
The units also have two pressure transducers that are con-
nected to the low side of the system. These two pressure trans-
ducers measure the low side pressure and are used for low pres-
sure protection and coil freeze protection.
By using the Saturated Condensing Temperature Sensors
and the low side pressure transducers, the ComfortLink control
displays the high and low side pressures and saturation temper-
atures and a normal gage set is not required.
SMOKE DETECTOR — The units can be equipped with an
optional smoke detector located in the return air. The detector
iswiredtotheComfortLink controls and, if activated, will stop
the unit by means of a special fire mode. The smoke detector
can also be wired to an external alarm system through TB5 ter-
minals 10 and 11. The sensor is located in the return air section
behind the filter access door.
FILTER STATUS SWITCH — The units can be equipped
with an optional filter status switch. The switch measures the
pressure drop across the filters and closes when an adjustable
pressure set point is exceeded. The sensor is located in the
return air section behind the filter access door.
RETURN AIR CO
2
SENSOR — The unit can also be
equipped with a return air IAQ CO
2
sensor that is used for the
demand control ventilation. The sensor is located in the return
air section and can be accessed from the filter access door.
BOARD ADDRESSES — Each board in the system has an
address. The MBB has a default address of 1 but it does have
an instance jumper that should be set to 1 as shown in Fig. 22.
For the other boards in the system there is a 4-dip switch head-
er on each board that should be set as shown below.
Board Address Settings
0=On; 1=Off
Table 99 — VFD Terminal Designations
BOARD SW1 SW2 SW3 SW4
ECB10000
ECB21000
SCB0000
CEM0000
TERMINAL FUNCTION
U1
V1
W1 Three-Phase Main Circuit Input Power Supply
U2
V2 Three-Phase AC Output to Motor, 0 V to
W2 Maximum Input Voltage Level
X1-11 (GND)
X1-12 (COMMON) Factory-supplied jumper
X1-10 (24 VDC)
X1-13 (DI-1) Run (factory-supplied jumper)
X1-10 (24 VDC) Start Enable 1 (factory-supplied jumper). When
X1-16 (DI-4) opened the drive goes to emergency stop.
X1-2 (AI-1)
X1-3 (AGND) Factory wired for 4 to 20 mA remote input
Fig. 27 — VFD Wiring
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