148
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 net-
work communication. The other boards do not have a CCN
communications port.
CARRIER COMFORT NETWORK
®
INTERFACE —
The 48/50N Series units can be connected to the CCN if
desired. The communication bus wiring is a shielded, 3-con-
ductor 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 arrangement. The positive pin of each sys-
tem element communication connector must be wired to the
positive pins of the system elements on either side of it. This is
also required for the negative and signal ground pins of each
system element. Wiring connections for CCN should be made
at the COMM board. See Fig. 39. Consult the CCN Contrac-
tor's Manual for further information.
NOTE: Conductors and drain wire must be 20 AWG (Ameri-
can 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 temperature 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
entirely within one building, the resulting continuous shield
must be connected to a ground at one point only. If the commu-
nication bus cable exits from one building and enters another,
the shields must be connected to grounds at the lightning sup-
pressor 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 the COMM
board, the white wire to COM terminal on the COMM
board, and the black wire to the (-) terminal on the
COMM board.
4. The RJ14 CCN connector on the COMM board can also
be used, but is only intended for temporary connection
(for example, a laptop computer running Service Tool).
Restore power to unit.
Through the Navigator display, the user can access all the
inputs and outputs to check on their values and status. Because
the unit is equipped with suction pressure transducers and dis-
charge saturation temperature sensors, the Navigator display
can also display pressures typically obtained from gages. The
control includes a full alarm history, which can be accessed
from the display. In addition, through the Navigator display the
user can access a built-in test routine that can be used at start-
up commission and to diagnose operational problems with the
unit. The Navigator display is located in the control box and is
standard on all units.
SUPPLY FAN — The 48/50N units are equipped with a sin-
gle air-foil type supply fan. The units have an optional high and
low fan that can be selected to match the airflow requirements
of the application. Additionally, the motor horsepower size for
the supply fan is also selected to match the airflow require-
ments of the application. The fan sleds are spring isolated and
driven by a single 3-phase motor. The fan is controlled directly
by the ComfortLink controls.
VARIABLE FREQUENCY DRIVE (VFD) — Supply fans
are powered and controlled with VFDs. The supply fan VFD is
located in the supply fan section behind an access door. Units
equipped with optional power exhaust or return fans will also
be powered and controlled with a VFD. The VFD for the pow-
er exhaust or return fan is located in the return section behind
an access door.
The N Series units use ABB VFDs. The VFDs communi-
cate to the ComfortLink MBB over the local equipment net-
work (LEN). The VFD speed is controlled directly by the
ComfortLink controls over the LEN. The interface wiring for
the VFDs is shown in Fig. 40 and the terminal designations are
shown in Table 107. The VFD has a keypad display panel that
can be used for service diagnostics and setting the initial VFD
parameters required to allow the VFD to communicate on the
LEN. Additional VFD parameters are set by the ComfortLink
controls, and sent to the VFD over the LEN at power up of the
VFD. The VFD faults can be reset with the VFD keypad or
through the ComfortLink controls (Alarms
R.CUR =Yes).
POWER EXHAUST — The units can be equipped with an
optional power exhaust system. The power exhaust fan is a
belt-driven forward-curved fan. For modulating (CV or VAV)
applications, the fan is controlled by the ComfortLink controls
based on building pressure sensed by the building pressure
transducer. The fan speed is modulated to maintain the building
pressure set point.
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.
* Registered trademark of DuPont.
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