Chapter 9 Electrical Wiring Diagram Basics 217
Copyright Goodheart-Willcox Co., Inc.
9.4.3 Outdoor Controls on a
Ducted Heating and Cooling System
The schematic wiring diagram for the outdoor unit of
a split air-conditioning system is shown in Figure 9-25.
Converting this schematic to a ladder diagram,
Figure 9-26, shows that the system compressor and
condenser fan motor cycle on and off together, as long
as the CC1 and CC2 contacts on the contactor are
closed.
Most air-conditioning systems are protected by
both high-pressure and low-pressure switches. These
controls are wired in series with the contactor coil and
prevent the compressor from operating if the system’s
operating pressure gets either too high or too low.
Power supply
208/230 V
Single-phase, 60 Hz
BK
RED
BR BR
W
W
BK
YEL
BK
BK
BK
BK
RC RC
C
R
S
YEL
BL BL ORG
ORG
Low-voltage
Power supply
40 VA/24 V
COMP
CFM
LPS
CC
CC1
CC2
HPS
Goodheart-Willcox Publisher
Figure 9-25. Schematic wiring diagram of the outdoor unit of a split air-conditioning
system.
Goodheart-Willcox Publisher
Figure 9-26. Ladder wiring diagram of the outdoor unit of a
split air-conditioning system.
CC1
L1 L2
RC
RC
C
S
R
COMP
CFM
LPS HPS
CC
CC2
OL
24 V control circuit