48/50Hc 17-28 Units - Low Voltage Terminal Boards; (Tb A And Tb B); Communication Interface Board (Cib); Central Terminal Board (Ctb) - Carrier 48HC 04-28 Controls, Start-Up, Operation And Troubleshooting

48/50HC 17-28 Units — Low Voltage Terminal
Boards (TB A and TB B)
There are two terminal boards with 16 terminals each, and ori-
ented one mounted above the other. The front have screw ter-
minals and the back have spade connectors. These terminal
boards provide a connection point for the thermostat or space
sensor and for most field-installed accessories. See Table 33.

Communication Interface Board (CIB)

This circuit board provides a field connection point for unit
communications. The Local Equipment Network (LEN) RJ-11
connector allows a hand-held Navigator to be plugged in to ac-
cess the unit's menus. The Carrier Comfort Network
RJ-11 connector or the CCN screw terminals allow building
communication connections. See Fig. 35.
LEN CCN
Fig. 35 — Communications Interface Board (CIB)

Central Terminal Board (CTB)

This circuit board is a simple trace board that serves as a junc-
tion point between components and the ComfortLink system. It
is the distribution center for transformer 1's power. The inte-
grated gas controller (IGC), electric heater control, compressor
control, and unit shutdown all feed through this trace board.
See Fig. 36 and Table 34 for the connections through this
board.
Table 33 — Upper and Lower Field Connection Terminal (TB A and TB B) Board Connections (17-28 Size Units)
TERMINAL TERMINAL
BLOCK LABEL
C- 2
R- 2
SPT+
SPT-
SPTO
FDWN
Upper
(TB A)
X
G
W1
W2
Y1
Y2
RAT
SAT
HUM
LPWR
COM
Lower
IAQ
(TB B)
SPRH
RMOC
ENTH
R- 2
C- 2
*Point name displayed on the scrolling marquee or Navigator™ display.
® (CCN)
(+) (com) (-) shield
CCN
DISPLAY
DESCRIPTION
NAME*
Transformer 2 Common
24 VAC power Transformer 2
SPT Space temperature (T55/56)
SPT Space temperature (T55/56)
SPTO Space temperature offset (T56)
FDWN Fire shutdown switch input
ALRM Alarm output (normally open)
G Thermostat G (Fan)
W1 Thermostat W1 (1st stage heat)
W2 Thermostat W2 (2nd stage heat)
Y1 Thermostat Y1 (1st stage cool)
Y2 Thermostat Y2 (2nd stage cool)
RAT Return Air Temperature Sensor
SAT Supply Air Temperature Sensor
HUM Humidistat switch input
Analog Sensor Loop power
(24vdc)
Analog sensor common
IAQ Indoor air quality sensor
Relative humidity sensor or
SP.RH or OAQ
Outdoor air quality sensor
RM.OC Remote occupancy switch
ENTH or IAQ.S Outdoor enthalpy switch, or
Indoor air quality switch
24 VAC power Transformer 2
Transformer 2 Common
Fig. 36 — Central Terminal Board (CTB)
SENSOR
LOCATION
space
space
space
supply/return/
space
space
space
space
space
space
space
return duct
Blower or duct
supply/return/
space
return/space
field installed
field installed
economizer, or
return/space
82
TERMINAL
TYPE OF I/O
NUMBER
24 VAC common 1,3,4
24 VAC 13,15,16
10k thermistor 8
10k thermistor 7
10k thermistor 5
24 VAC input 11
24 VAC output 2
24 VAC input 6
24 VAC input 8
24 VAC input 10
24 VAC input 12
24 VAC input 14
10k thermistor 1,3
10k thermistor 5,7
switch input 9
24 VDC 8
Ground 4
4- 20 mA input 6
4-20 mA input 2
24 VAC input 10
24 VAC input 12
24 VAC 15
24 VAC common 16