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THERMISTORS AND PRESSURE TRANSDUCERS —
The 48/50A2,A3,A4,A5 units are equipped with four pressure
transducers. These units have two pressure transducers con-
nected to the low side of the system and two pressure transduc-
ers connected to the high side of the system.
By using either temperature sensors or transducers, the
ComfortLink controller displays the high and low side pres-
sures and saturation temperatures. 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
is wired to the ComfortLink 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
terminals 10 and 11. The sensor is located in the return air sec-
tion 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 setpoint is exceeded. The sensor is located in the
return air section behind the filter access door.
RETURN AIR CO
SENSOR — The unit can also be
2
equipped with a return air IAQ CO
demand controlled ventilation. The sensor is located in the re-
turn 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. 29.
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
SW1
ECB1
0
ECB2
1
SCB
0
CEM
0
0 = On; 1 = Off
FIELD CONNECTION TERMINAL STRIPS — Field con-
nection terminal strips are located in the main control box. See
Fig. 36 and Table 110.
Accessory Control Components —
the factory-installed options, the units can also be equipped
with several field-installed accessories that expand the control
features of the unit. The following hardware components can
be used as accessories.
ROOM
THERMOSTATS
ONLY) — The ComfortLink controls support a conventional
electro-mechanical or electronic thermostat that uses the Y1,
Y2, W1, W2, and G signals. The control also supports an addi-
tional input for an occupied/unoccupied command that is avail-
able on some new thermostats. The ComfortLink controls can
be configured to run with multiple stages of capacity which al-
lows up to 6 stages of capacity. Although the unit can be con-
figured for normal 2-stage control, it is recommended that the
multi-stage control be used. The room thermostat is connected
to TB4.
SPACE SENSOR — The ComfortLink controls support the
use of space temperature sensors. The T55 and T56 sensors
and CCN communicating T58 room sensor can be used. The
T55 and T56 sensors are connected to TB5 terminal 3, 4, and 5.
The T58 sensor is connected to the CCN connections on TB3.
When a T55, T56, or T58 sensor is used, the user must install
the red jumpers from R to W1, and W2 on TB4 for the heat
function to work correctly.
SPACE CO
SENSORS — The ComfortLink controls also
2
support a CO
IAQ sensor that can be located in the space for
2
use in demand ventilation. The sensor must be a 4 to 20 mA
sensor that is used for the
2
SW2
SW3
SW4
0
0
0
0
0
0
0
0
0
0
0
0
In addition to
(48/50A2,A4
UNITS
sensor and should be connected to TB5 terminal 6 and 7. See
Fig. 37 for sensor wiring.
ECONOMIZER
HUMIDITY
SORS — The ComfortLink controls support 5 different
changeover schemes for the economizer. These are:
• outdoor air dry bulb
• differential dry bulb
• outdoor air enthalpy curves
• differential enthalpy
• custom curves (a combination of an enthalpy/dewpoint
curve and a dry bulb curve).
The units are equipped as standard with an outside air and
return air dry bulb sensor which supports the dry bulb change-
over methods. If the other methods are to be used, then a field-
installed humidity sensor must be installed for outdoor air en-
thalpy and customer curve control and two humidity sensors
must be installed for differential enthalpy. Installation holes are
pre-drilled and wire harnesses are installed in every unit for
connection of the humidity sensors. The ComfortLink controls
convert the measured humidity into enthalpy, dewpoint, and
the humidity changeover curves.
MOTORMASTER
®
32 F when an economizer is not used, the units can be equipped
with an accessory Motormaster V control, which controls the
speed of the stage 1 condenser fans. The Motormaster V control
is a 3-phase inverter that controls the speed of the fans based on
a pressure transducer connected to the liquid line. On 48/
50A020-035 units, one fan will be controlled. On 48/50A040-
060 units, two fans will be controlled. For units equipped with
an economizer, there should not be a need for this control be-
cause the economizer can provide free cooling using outside air,
which will be significantly lower in operating cost.
The accessory Motormaster V speed control is a completely
self-contained control and is not controlled by the unit's
ComfortLink controller. On 48/50A 060 units with 6 fan mo-
tors, the Motormaster control configuration (M.M.) must be set
to YES.
ACCESSORY NAVIGATOR™ DISPLAY — The accessory
handheld Navigator display can be used with the 48/50A Series
units. See Fig. 38. The Navigator display operates the same
way as the scrolling marquee device. The ECB1 and ECB2
boards contain a second LEN port (J3 connection) than can be
used with the handheld Navigator display.
CONTROL MODULE COMMUNICATIONS
Red LED — Proper operation of the control boards can be
visually checked by looking at the red status LEDs as shown on
Fig. 29-33. When operating correctly, the red status LEDs
should blink in unison at a rate of once every 2 seconds. If the
red LEDs are not blinking in unison, verify that correct power is
being supplied to all modules. Also, be sure that the main base
board is supplied with the current software. If necessary, reload
current software. If the problem still persists, replace the MBB.
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 boards also have a green LED, which is
the indicator of the operation of the LEN communications,
which is used for communications between the boards. On the
MBB board the Local Equipment Network (LEN) LED should
always be blinking whenever power is on. All other boards
have a LEN LED that will blink whenever power is on and
there is communication occurring. If LEN LED is not blinking,
check LEN connections for potential communication errors (J3
and J4 connectors). A 3-wire sensor bus accomplishes commu-
nication between modules. These 3 wires run in parallel from
module to module.
Yellow LED — The MBB has one yellow LED. The Carrier
Comfort Network
®
(CCN) LED will blink during times of
network communication. The other boards do not have a CCN
communications port.
125
CHANGEOVER
V CONTROL — For operation below
SEN-
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