Ecobee Smart Si Installation Manual page 16

Before
24V
C
1-stage AC
After
24V
C
1-stage AC
Smart Si Thermostat
Use jumper wire included in box to connect Y and G on the furnance
Repurpose the original G wire as C wire. Note that the furnance controls the fan in this
configuration.
Original Thermostat
Repurpose G
wire as C wire
W2
Y2 C RH RC
AUX
Single stage heat/cool with 4 wires at thermostat
HUM
R G W Y R
HUM
W
G Y N/C
O/B
Y
W
G
R
C
1-stage Furnace
Y
Use jumper
wire included
W
in box
G
R
C
1-stage Furnace
11