Carrier 48AJ Operating And Service Manual page 116

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
changeover methods. If the other methods are to be used, then a
field-installed humidity sensor must be installed for outdoor air
enthalpy 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 control
converts the measured humidity into enthalpy, dewpoint, and
the humidity changeover curves.
MOTORMASTER® V CONTROL — For operation below
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 48/50A036-
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 control. On 48/50A051 and 060 units, the
Motormaster control configuration (M.M.) must be set to YES.
See page 38.
ACCESSORY NAVIGATOR™ DISPLAY — The accesso-
ry handheld Navigator display can be used with the 48/50A se-
ries units. See Fig. 30. 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. 22-25. 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.
CARRIER COMFORT NETWORK INTERFACE — The
48/50A series units can be connected to the CCN if desired. The
CHANGEOVER SEN- communication bus wiring is a shielded, 3-conductor cable with
drain wire and is field supplied and installed. See the Installation
instructions for wiring information. The system elements are
connected to the communication bus in a daisy chain arrange-
ment. The positive pin of each system element communication
connector must be wired to the positive pins of the system ele-
ments on either side of it. This is also required for the negative
and signal ground pins of each system element. Wiring connec-
tions for CCN should be made at TB3. See Fig. 31. Consult the
CCN Contractor's Manual for further information.
NOTE: Conductors and drain wire must be 20-AWG
(American Wire Gage) minimum stranded, tinned copper.
Individual conductors must be insulated with PVC, PVC/
nylon, vinyl, Teflon, or polyethylene. An aluminum/polyester
100% foil shield and an outer jacket of PVC, PVC/nylon,
chrome vinyl, or Teflon with a minimum operating tempera-
ture range of –20 C to 60 C is required.
It is important when connecting to a CCN communication
bus that a color-coding scheme be used for the entire network
to simplify the installation. It is recommended that red be used
for the signal positive, black for the signal negative and white
for the signal ground. Use a similar scheme for cables contain-
ing different colored wires.
At each system element, the shields of its communication
bus cables must be tied together. If the communication bus is en-
tirely within one building, the resulting continuous shield must
be connected to a ground at one point only. If the communica-
tion bus cable exits from one building and enters another, the
shields must be connected to grounds at the lightning suppressor
in each building where the cable enters or exits the building (one
point per building only). To connect the unit to the network:
1. Turn off power to the control box.
2. Cut the CCN wire and strip the ends of the red (+), white
(ground), and black (–) conductors. (Substitute appropri-
ate colors for different colored cables.)
3. Connect the red wire to (+) terminal on TB3 of the plug,
the white wire to COM terminal, and the black wire to the
(–) terminal.
4. The RJ14 CCN connector on TB3 can also be used, but is
only intended for temporary connection (for example, a
laptop computer running Service Tool).
5. Restore power to unit.
IMPORTANT: A shorted CCN bus cable will prevent
some routines from running and may prevent the unit
from starting. If abnormal conditions occur, unplug the
connector. If conditions return to normal, check the
CCN connector and cable. Run new cable if necessary.
A short in one section of the bus can cause problems
with all system elements on the bus.
Fig. 30 — Accessory Navigator Display
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