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19
CONTROLS
General —
The 30RAP air-cooled scroll chillers contain
the ComfortLink™ electronic control system that controls and
monitors all operations of the chiller.
The control system is composed of several components as
listed in the sections below. See Fig. 3-5 for typical control box
drawings. See Fig. 6 and 7 for control schematics.
Main Base Board (MBB) — See Fig. 8. The MBB is
the heart of the ComfortLink control system. It contains the
major portion of operating software and controls the operation
of the machine. The MBB continuously monitors input/output
channel information received from its inputs and from all other
modules. The MBB receives inputs from the discharge and
suction pressure transducers and thermistors. See Table 15. The
MBB also receives the feedback inputs from each compressor
current sensor board and other status switches. See Table 16.
The MBB also controls several outputs. Relay outputs con-
trolled by the MBB are shown in Table 17. Information is
transmitted between modules via a 3-wire communication bus
or LEN (Local Equipment Network). The CCN (Carrier Com-
fort Network) bus is also supported. Connections to both LEN
and CCN buses are made at the LVT (low voltage terminal).
See Fig. 8.
Energy Management Module (EMM) — The EMM
module is available as a factory-installed option or as a field-
installed accessory. The EMM module receives 4 to 20 mA
inputs for the leaving fluid temperature reset, cooling set point
and demand limit functions. The EMM module also receives
the switch inputs for the field-installed 2-stage demand limit
and ice done functions. The EMM module communicates the
status of all inputs with the MBB, and the MBB adjusts the
control point, capacity limit, and other functions according to
the inputs received.
Current Sensor Board (CSB) — The CSB is used to
monitor the status of the compressors by measuring current and
providing an analog input to the main base board (MBB) or
compressor expansion module (CXB).
AUX Board (AUX) — The AUX is used with the digital
scroll option and the low ambient head pressure option. It pro-
vides additional inputs and outputs for digital scroll control
along with analog outputs to control head pressure control fan
speeds.
Expansion Valve Board (EXV) — The EXV board
communicates with the MBB and directly controls the expan-
sion valves to maintain the correct compressor superheat.
Enable/Off/Remote Contact Switch — The Enable/
Off/Remote Contact switch is a 3-position switch used to
control the chiller. When switched to the Enable position the
chiller is under its own control. Move the switch to the Off
position to shut the chiller down. Move the switch to the
Remote Contact position and a field-installed dry contact can
be used to start the chiller. The contacts must be capable of
handling a 24 vac, 50-mA load. In the Enable and Remote
Contact (dry contacts closed) positions, the chiller is allowed to
operate and respond to the scheduling configuration, CCN
configuration and set point data. See Fig. 9.
Emergency On/Off Switch — The Emergency On/Off
switch should only be used when it is required to shut the
chiller off immediately. Power to the MBB, EMM, and
marquee display is interrupted when this switch is off and all
outputs from these modules will be turned off.
Board Addresses — The main base board (MBB) has a
3-position instance jumper that must be set to ‘1.’ The elec-
tronic expansion valve board (EXV) and energy management
board (EMM) have 4-position DIP switches. All switches are
set to ‘On’ for these boards. The auxiliary board (AUX) has an
8-position DIP switch. Switches 2, 5, and 7 are set to ‘On.’
Control Module Communication
RED LED — Proper operation of the control boards can be
visually checked by looking at the red status LEDs
(light-emitting diodes). When operating correctly, the red status
LEDs should be blinking 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. Be sure that
the main base board (MBB) is supplied with the current soft-
ware. If necessary, reload current software. If the problem still
persists, replace the MBB. A red 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 MBB has one green LED. The Local
Equipment Network (LEN) LED should always be blinking
whenever power is on. All other boards have a LEN LED
which should be blinking whenever power is on. Check LEN
connections for potential communication errors at the board J3
and/or J4 connectors. Communication between modules is
accomplished by a 3-wire sensor bus. These 3 wires run in
parallel from module to module. The J4 connector on the MBB
provides both power and communication directly to the
marquee display only.
YELLOW LED — The MBB has one yellow LED. The
Carrier Comfort Network (CCN) LED will blink during times
of network communication.
Carrier Comfort Network
®
(CCN) Interface —
The 30RAP chiller units can be connected to the CCN if
desired. The communication bus wiring is a shielded,
3-conductor cable with drain wire and is supplied and installed
in the field. See Table 18. The system elements are connected
to the communication bus in a daisy chain arrangement. The
positive pin of each system 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 LVT. 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. Wire manufactured by Alpha (2413
or 5463), American (A22503), Belden (8772), or Columbia
(02525) meets the above mentioned requirements.
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
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.)