Unit installation

48
Table 16 – Main Base Board (MBB) Connections
DISPLAY
NAME
POINT DESCRIPTION SENSOR L OCATION TYPE OF I/O
CONNECTION
PIN NUMBER
INPUTS
Input power from TRAN2 control box 24 VAC J 1 , 1 --- 3
IGC.F IGC Fan Request gas section switch input J6, 4
FDWN Fire shutdown switch supply/return/space switch input J6, 6
G Thermostat G (Fan) space switch input J7, 2
W2 Thermostat W2 (2nd Stage Heat) space switch input J7, 4
W1 Thermostat W1 (1st Stage Heat) space switch input J7, 6
Y2 Thermostat Y2 (2nd Stage Cool) space switch input J7, 8
Y1 Thermostat Y1 (1st Stage Cool) space switch input J7, 10
FIL.S Filter status switch indoor fan section switch input J 9 , 2 --- 3
HUM Humidistat switch input space switch input J 9 , 5 --- 6
Not Used 0--- 5vdc digital input J 9 , 7 --- 9
Not Used 0--- 5vdc digital input J 9 , 1 0 --- 1 2
SPT Space temperature (T55/56) space 10k thermistor J 8 , 1 --- 2
SPTO Space temperature offset (T56) space 10k thermistor J 8 , 2 --- 3
OAT Outdoor air temperature outdoor coil support 10k thermistor J 8 , 5 --- 6
SAT Supply air temperature
indoor fan housing, or
supply duct
10k thermistor J 8 , 7 --- 8
SCT.A Saturated condenser temperature, circuit A outdoor coil, circuit A 5k thermistor J 8 , 9 --- 1 0
Not Used 5k thermistor J 8 , 1 1 --- 1 2
RAT Return Air Te mpe rature Re turn 10k thermistor J 8 , 1 3 --- 1 4
FAN.S Fan status switch indoor fan section switch input J 8 , 1 5 --- 1 6
SSP.A Suction pressure, circuit A compressor A suction pipe
0 --- 5 V D C p r e s s u r e
transducer
J 8 , 1 8 --- 2 0
Not Used
0 --- 5 V D C p r e s s u r e
transducer
J 8 , 2 1 --- 2 3
Not Used 0 --- 5 V D C J 8 , 2 4 --- 2 6
OUTPUTS
L.ODF Low Ambient Outdoor Fan relay J10, 3
Not Used relay J10, 6
Not Used relay J10, 9
IDF.1 Indoor Fan Speed relay 1 relay J10, 11
IDF.2 Indoor Fan Speed relay 2 relay J10, 13
IDF.3 Indoor Fan Speed relay 3 relay J10, 16
ALRM Alarm relay relay J10, 19
COMP.A Circuit A Compressor relay J10, 21
LDR.A Circuit A Loader relay J10, 23
HT.1 Heat Stage 2 relay relay J10, 25
HT.2 Heat Stage 1 relay relay J10, 27
COMMUNICATION
Local Equipment Network (LEN) communication J 5 , 1 --- 3
Carrier Comfort Network (CCN) communication J 5 , 5 --- 7
Network device power 24 VAC J 5 , 9 --- 1 0
Scrolling Marquee Display (LEN) communication J 4 , 1 --- 3
Scrolling Marquee Display power 24 VAC J 4 , 5 --- 6
Expansion LEN Bus communication J 3 , 1 --- 3
Optional ECB power 24 VAC J 2 , 1 --- 2
48/50LC