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5168273-YIM-A-1115
W1
W2
Y1
G
Y2
THERMOSTAT
WIRED HERE
OCC
X
R
SD-24
C
Figure 22: Unit Control Board
Table 19: Simplicity SE UCB Details
Limit, 24 VAC power and shutdown connections from unit wiring harness at left on upper edge of UCB
LIMIT
C
24V
SD 24
SD R
R
44
Description
Terminal Directional orientation: viewed with silkscreen labels upright
Monitored 24 VAC input through heat section limit
switch(es)
24 VAC, 75 VA transformer Common referenced
to cabinet ground
24 VAC, 75 VA transformer hot
24 VAC hot out for factory accessory smoke
detector, condensate overflow and/or user
shutdown relay switching in series
24 VAC hot return from factory accessory smoke
detector, condensate overflow and user shutdown
relay switching in series
24 VAC hot for switched inputs to the UCB
Function & Comments
If voltage is absent, indicating the heat section is over-
temperature, the UCB will bring on the indoor blower
Connects through circuit traces to thermostat connection strip C
and indoor blower VFD pin C
Powers the UCB microprocessor, connects through circuit trace
to the SD 24 terminal
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
Connects through circuit trace to the R terminal on the upper left
of the board
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
Johnson Controls Unitary Products
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