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15. Replace thermostat cover by snapping into place.
16. Turn on power to system. Test thermostat as described in the
following section.
Step 3: Testing the Thermostat
WARNING: DO NOT SHORT (JUMPER) ACROSS TERMINALS
OF GAS VALVE OR SYSTEM CONTROL TO TEST
OPERATION. THIS WILL DAMAGE THE
THERMOSTAT AND VOID YOUR WARRANTY.
CAUTION: DO NOT SWITCH SYSTEM TO COOL IF THE TEMPERATURE
IS BELOW 50°F (10°C). THIS CAN DAMAGE THE AIR
CONDITIONING SYSTEM AND CAUSE PERSONAL INJURY.
1. Place the EMER-HEAT-OFF-COOL switch into
the COOL position. The display will read COOL.
2. Press the
ٚ
button until the temperature setting
is at least 3 degrees below the room temperature.
The air conditioning system should turn on within
a few seconds. The snowflake icon will be displayed
( 1
st
stage cooling; 2
nd
stage cooling).
6
TERMINAL LEGEND - 9420
TERM EQUIPMENT TO CONNECT REQ? TERMINAL FUNCTION
C 24VAC common connection Yes For input of 24VAC common
side of transformer
L System fault indicator connection No For connection of system
fault indicator (if present)
R 24VAC hot connection Yes For input of 24VAC hot side
of transformer
Y2 Second stage cooling connection No Energizes on a call for
second stage cooling
Y1 First stage compressor connection Yes Energizes on a call for
first stage of heating and
cooling
E Emergency heat connection No* Energizes on a call for heat
in the EM mode only
G Indoor fan connection Yes Energizes with E, Y1, Y2 and
W2 terminals or with FAN
option switched to the ON
position
W2 Second stage heat connection No* Energizes on a call for
second stage of heat
(auxiliary heat)
O Cool active reversing Yes** Energizes when in the in
valve connection COOL mode
B Heat active reversing Yes** Energizes when in the
valve connection HEAT or EM modes
* For systems using a backup heat source. If separate E terminal connection is not available,
jumper E and W2.
** Most heat pump systems will have a cool active or a heat active reversing valve. Use the
appropriate terminal.
!