5370597-JIM-D-1019
Johnson Controls Ducted Systems
53
Table 29: Smart Equipment™ UCB Details
Description
Function & Comments
Terminal Directional orientation: viewed with silkscreen labels upright
Limit, 24 VAC power and shutdown connections from unit wiring harness at left on upper edge of UCB
LIMIT
Monitored 24 VAC input through heat section limit
switch(es)
If voltage is absent, indicating the heat section is over-
temperature, the UCB will bring on the indoor blower
C
24 VAC, 75 VA transformer Common referenced
to cabinet ground
Connects through circuit traces to thermostat connection strip C
and indoor blower VFD pin C
24V
24 VAC, 75 VA transformer hot
Powers the UCB microprocessor, connects through circuit trace
to the SD 24 terminal
SD 24
24 VAC hot out for factory accessory smoke
detector, condensate overflow and/or user
shutdown relay switching in series
Connects through circuit trace to thermostat connection strip
SD-24. A wiring harness jumper plug connecting SD 24 to SD R
is in place if factory accessories for unit shutdown are not used -
this jumper plug must be removed if the switching of field-added
external accessories for unit shutdown are wired between
thermostat connection strip SD-24 and R
SD R
24 VAC hot return from factory accessory smoke
detector, condensate overflow and user shutdown
relay switching in series
Connects through circuit trace to the R terminal on the upper left
of the board
R
24 VAC hot for switched inputs to the UCB
Connects through circuit trace to the thermostat connection
strip R terminal, right FAN OVR pin, right HPS1 pin, right HPS2
pin, lower DFS pin and lower APS pin
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
