
O/W2
Y1
R
G
Y/Y2
W/W1
C
B
L
DO NOT USE
S1
S2
COMMERCIAL THERMOSTAT
CONNECTION
BOARD
R
Y1
 Y2
 Y2
W1
W2
G
C
X*
*Does not apply to 558D and 
NOTES:
1.558D and 
2.For 548D and 549B heat pump applications, set switch A to OFF (air conditioning). The 548D and 549B units do not have an ``O'' terminal.
Fig. 1 Ð Thermostat Wiring (548D036-120;  549B036-120;  551B036-150; 
558D036-150;  580D036-150;  581B036-150) 
O/W2
Y1
R
G
Y/Y2
W/W1
C
B
L DO NOT USE S1 S2
TB2

 W2
 W2
 W1
 W1

 R
 R
C

 Y1
 Y1
 Y2
 Y2
G
X
COMMERCIAL
THERMOSTAT