3
Power options
Base plate wiring terminal designations
L/A
- A
Not used
O/B Changeover valve
Y
Compressor contactor
(stage 1)
AUX -
W2
Auxiliary heat
(PSTSN21AWH Only)
Y2
Not used E
Emergency heat
(PSTSN21AWH Only)
G
Fan W Heat (stage 1)
C
24VAC common. For 2
transformer systems,
use common wire from
cooling transformer.
K Not Used
R
24VAC power from heating
transformer*
Rc
24VAC power from cooling
transformer*
Note: Not all
terminals may be
used, depending
on the system
type that is being
wired. The most
commonly used
terminals are
shaded.
* Terminal can be jumped using Slider Tab. See “Setting Slider Tabs” above.
Y2
G
C
Y
A
Rc
W
K
W2
R
L/A
O/B
AUX
E
M39345
Set R Slider Tab.
• Use built-in jumper (R Slider Tab)
to differentiate between one or two
transformer systems.
• If there is only one R wire, and it is
connected to the R, Rc, or RH terminal, set
the slider to the up position (1 wire).
• If there is one wire connected to the R
terminal and one wire connected to the
Rc terminal, set the slider to the down
position (2 wires).
Setting slider tabs
Insert R and C wires into
designated terminals
for primary AC power
(C terminal is optional
if batteries are installed,
but it is recommended).
Remove wires by
depressing the terminal
tabs.
Insert AA batteries for primary or
backup power.
R/Rc Slider Tab
(built-in jumper)
Base Plate
Mounting System