5188235-YIM-E-0518
Johnson Controls Ducted Systems
67
Terminal Space temperature sensor connections at center on upper edge of UCB
ST
Space Temperature sensor input from 10KΩ @
77°F, Type III negative temperature coefficient
thermistor
Positive of VDC circuit (3.625 VDC reading to COM with open
circuit), effective if “Thermo- stat-only Control” parameter is set
OFF, space sensor override momentary shorts ST to COM to
initiate/terminate temporary occupancy
COM
Common for ST and SSO inputs
Negative of VDC circuit for ST and SSO inputs
SSO
Space Sensor Offset input from 0 to 20KΩ
potentiometer
Positive of VDC circuit (3.625 VDC reading to COM with open
circuit), 10KΩ/2.5 VDC is 0°F offset, 0Ω/0 VDC is maximum
above offset and 20KΩ/3.4 VDC is maximum below offset from
active space temperature setpoint
Pin Temperature sensor connections at right on upper edge of UCB
SAT+
Supply Air Temperature sensor input from 10KΩ
@ 77
°
F, Type III negative temperature coefficient
thermistor
Input required for operation; 3.625 VDC reading SAT+ to SAT
–
with open circuit. Used in heat/cool staging cutouts, free cooling
operation, demand ventilation operation, comfort ventilation
operation, economizer loading operation, VAV cooling
operation, hydronic heat operation.
RAT+
Return Air Temperature sensor input from 10KΩ
@ 77°F, Type III negative temperature coefficient
thermistor
Input required for operation; 3.625 VDC reading RAT+ to RAT
–
with open circuit. Used in return air enthalpy calculation.
Substitutes for space temperature if no other space
temperature input is present.
OAT+
Outside Air Temperature sensor input from 10KΩ
@ 77°F, Type III negative temperature coefficient
thermistor
Input required for operation but may be a communicated value;
3.625 VDC reading OAT+ to OAT
–
with open circuit. Used in
heat/cool cutouts, low ambient cooling determination, dry bulb
free cooling changeover, outside air enthalpy calculation,
economizer loading operation, heat pump demand defrost
calculation.
CC1+
#1 refrigerant circuit Condenser Coil temperature
sensor input from 10KΩ @ 77°F, Type III negative
temperature coefficient thermistor
Input required for heat pump units, not required for A/C units;
3.625 VDC reading CC1+ to CC1
–
with open circuit. Used in
heat pump demand defrost calculation.
EC1+
#1 refrigerant circuit Evaporator Coil temperature
sensor input from 10KΩ @ 77°F, Type III negative
temperature coefficient thermistor
Input required for operation; 3.625 VDC reading EC1+ to EC1
–
with open circuit. Used in suction line temperature safety.
CC2+
#2 refrigerant circuit Condenser Coil temperature
sensor input from 10KΩ @ 77°F, Type III negative
temperature coefficient thermistor
Input required for 2-compressor heat pump units, not required
for 2-compressor A/C units, not active for 1-compressor units;
3.625 VDC reading CC2+ to CC2
–
with open circuit. Used in
heat pump demand defrost calculation.
EC2+
#2 refrigerant circuit Evaporator Coil temperature
sensor input from 10KΩ @ 77°F, Type III negative
temperature coefficient thermistor
Input required for operation of 2-compressor units, not active for
1-compressor units; 3.625 VDC reading EC2+ to EC2
–
with
open circuit. Used in suction line temperature safety.
Pinned connections on right edge of UCB
RAH+
Return Air Humidity input from 0-10 VDC @ 0-
100% RH sensor
Input required for reheat units, optional in all other units, may be
a communicated value. Used in return air enthalpy calculation,
temperature/humidity setpoint reset, reheat operation.
DCT PRS+
Supply Duct Pressure input from 0-5 VDC @ 0-5”
w.c. sensor
Input required for variable air volume units. Used in VAV indoor
blower operation.
DFS (upper pin)
24 VAC hot return from Dirty Filter Switch
Optional input; switch closure for greater than 15 seconds
during indoor blower operation
initiates a notification alarm
DFS (lower pin)
24 VAC hot out for Dirty Filter Switch
Connects through circuit trace to the R terminal
Table 31: Smart Equipment™ UCB Details (Continued)
Description
Function & Comments
