5742640-TIM-A-0419
Johnson Controls Ducted Systems
67
Terminal Thermostat connection strip on left edge of UCB
W1
1st stage heating request, 24 VAC input switched
from R
Not effective for cooling-only units
W2
2nd stage heating request, 24 VAC input switched
from R
Not effective for cooling-only units or units with single-stage
heat sections
Y1
1st stage cooling request, 24 VAC input switched
from R
Y2
2nd stage cooling request, 24 VAC input switched
from R
Visible in the display menu when the #ClgStgs parameter is set
for 2 or more, also effective for economizer free cooling supply
air temperature reset when the #ClgStgs parameter is set for 1
or more
G
Continuous indoor blower request, 24 VAC input
switched from R
OCC
Occupancy request, 24 VAC input switched from
R
Must have the OccMode parameter set for External to be
effective
X
Hard lockout indicator, 24 volt output to a light
thermostat LED
R
24 VAC hot for thermostat switching and power
If field-added external accessories for unit shutdown are used,
24 VAC hot return from smoke detector, condensate overflow
and/or user shutdown relay switching in series
SD-24
If field-added external accessories for unit
shutdown are used, 24 VAC hot out for smoke
detector, condensate over- flow and/or user
shutdown relay switching in series
Unit wiring harness jumper plug for factory shutdown
accessories must be removed if the switching of field-added
external accessories for unit shutdown are wired between
thermo- stat connection strip SD-24 and R
C
24 VAC common for thermostat power
LEDs on left edge of UCB
POWER
Green UCB power indicator
Lit indicates 24 VAC is present at C and 24V terminals
FAULT
Red hard lockout, networking error and firmware
error indicator
1/2 second on/off flashing indicates one or more alarm is
currently active, 1/10th second on/off flashing indicates a
networking error (polarity, addressing, etc.) or a firmware error
(likely correctable with re-loading from USB flash drive)
SA BUS
Green UCB SA bus communication transmission
indicator
Lit/flickering indicates UCB SA bus communication is currently
active, off indicates the UCB is awaiting SA bus communication
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.
Table 34: Smart Equipment™ UCB Details (Continued)
Description
Function & Comments
