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Control unit wiring
Figure 21 shows the control unit wired to a wall display unit and the HVAC system. Wire colors are typical
thermostat wiring colors. The fuse is a mini ATO 2 amp.
Note: For heat pump HVAC systems, the orange wire (O) is the changeover valve.
Figure 21. Control unit wiring
HVAC system transformer
Most central HVAC systems have a common heating and cooling transformer. This is the factory default
setting for jumper JP1. In some cases you may have separate heating and cooling systems, each with their own
transformer. In that case, cut jumper JP1 and wire the heating transformer red wire to the RH terminal and the
cooling system transformer red wire to the RC terminal. Wire the cooling system’s 24 VAC Com to the control
unit’s 24 VAC Com terminal. Do not connect the heating system’s common wire to the control unit.
Wall display unit
J1 WDU
J2 RS-485
GND
+12VDC
Clock
Data
GND
12V
C
D
GND
D+
D-
Status
Heat 1
Heat 2
CO
Fan
Comp 1
Comp 2
JP1
Fuse
Control unit
HVAC system
24V COM
24V RH
24V RC
W1
W2/O
G
Y1
Y2
Blue
Red
White
Orange
Green
Yellow
Black
C-24VAC common
R-24VAC return
W1-Heat stage 1
W2/O-Heat stage 2
G-Fan
Y1-Comp stage 1
Y2-Comp stage 2
SW1
STD
S2
1
2
HP
OFF ON
J4 HVAC system
GND
RS-485 Data +
RS-485 Data -