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ICE CFA1120A-3360A & CGA3180A I&O Manual 03/2021 Rev.5
5.2 – Modulating Head Pressure Control
A 10K Nominal NTC Thermistor is connected to the “P1” and “P2” inputs for circuit 1 and circuit 2
respectively. When this sensor is connected, the “FCC IN” is ignored and the thermistor value is used
as the process variable when controlling the head pressure. The controller modulates the Outdoor Fan
Motor to maintain a 90ºF temperature setpoint. The controller will always use the greater value of P1
and P2 input as the reference point. In the event that the Thermistor is disconnected, the controller
reverts to the “FCC IN” input to control the Head Pressure of the system.
5.3– Freeze Stat
A 10K Nominal NTC Thermistor is connected to the “FS1” input on the PCB. If the Thermistor is
not connected, freeze protection will not be provided. If the Thermistor is connected, the control will
provide the freeze protection by turning the compressor Off at a temperature of 35ºF (+/- 2ºF) on the
Indoor Coil. The compressor will remain Off until the temperature measured is greater than 45ºF and
the anti-short cycle time has elapsed.
5.4– Onboard Thermostat
The Onboard Thermostat requires a 10K NTC thermistor to be connected to the “FS2” input. It also
requires that the MODBUS functionality is enabled via MODBUS. The Heating Setpoint, Cooling
Setpoint and Calibration of the sensor has to be configured via MODBUS. Once configuration is
complete, the unit has the capability to function autonomously to maintain the space temperature.
Discrete Registers:
Read with Function Code 02, Write to RW or WO registers with Function Code 05
ID
Description
Size
Data Format
R/W
1
Current Status of the Y1 Compressor Call
1 Bit
0 = no call, 1 = call
RW
2
Current Status of the Y2 Compressor Call
1 Bit
0 = no call, 1 = call
RW
3
Current Status of the Humidity Call
1 Bit
0 = no call, 1 = call
RW
4
Current Status of the G Fan Call
1 Bit
0 = no call, 1 = call
RW
5
Current Status of the W2 Electric Heating Call
1 Bit
0 = no call, 1 = call
RW
6
Current Status of the FCC Call
1 Bit
0 = no call, 1 = call
RO
7
High Pressure Switch 1 Status
1 Bit
0 = Open, 1 = Closed
RO
8
High Pressure Switch 2 Status
1 Bit
0 = Open, 1 = Closed
RO
9
Low Pressure Switch 1 Status
1 Bit
0 = Open, 1 = Closed
RO
10
Low Pressure Switch 2 Status
1 Bit
0 = Open, 1 = Closed
RO
11
OFM Mode Selection
1 Bit
0 = PWM, 1 = 0-10V
RO
12
IFM Mode Selectiion
1 Bit
0 = PWM, 1 = 0-10V
RO
13
Test Mode Status
1 Bit
0 = Normal Mode
1 = Test Mode
RO
14
Status of Compressor 1 Relay Output
1 Bit
0 = Off, 1 = Energized
RO
15
Status of Compressor 2 Relay Output
1 Bit
0 = Off, 1 = Energized
RO
16
Status of RH RelayOutput
1 Bit
0 = Off, 1 = Energized
RO
17
Status of W2 RelayOutput
1 Bit
0 = Off, 1 = Energized
RO
18
Enables or Disables the internal Thermostat Functionality
1 Bit
0 = Off, 1 = Energized
RW
19
Enables or disables reading the thermostat inputs in Modbus
mode
1 Bit
0 = Modbus only
1 = Read thermostat Inputs
Default is 0
RW
Table 6a. MODBUS Discrete Registers
