Chapter 9 Electrical Wiring Diagram Basics 213
Copyright Goodheart-Willcox Co., Inc.
A ladder diagram, as shown in Figure 9-15, can be
used to troubleshoot the unit. Assume the unit was set
to operate in the HIGH COOL mode, and the com-
pressor does not operate but the fan does. The prob-
lem can be isolated to the bottom rung of the ladder
diagram, which indicates one of the following issues:
■ The contacts L1-C are not closing.
■ The thermostat might be open.
■ The overload might be open.
■ The compressor or its starting components might
be defective.
■ There is a problem with the interconnecting
wiring in the compressor circuit.
9.4 Basic Split Air-Conditioning
System Wiring Diagrams
Split air-conditioning systems are comprised of two pieces of equipment
called the indoor and outdoor units. This is unlike air-conditioning sys-
tems where all four major system components are enclosed in one cabinet.
Each of the sections of a split air-conditioning system has its own power
supply and control devices. These control devices are powered through
the space thermostat. The space thermostat is also an integral part of an
air-conditioning system. The wiring diagram of a residential split air-con-
ditioning system is shown in Figure 9-16. Each of the components that
make up the system, the thermostat, indoor unit, and outdoor unit, and
their wiring diagrams will be discussed in the following sections.
Goodheart-Willcox Publisher
Figure 9-15. A ladder diagram for a typical window or through-
the-wall air-conditioning unit.
RC
L1 1
L1 3
L1 2
L1
T-STAT
L1 N
RC C
S
R
OL C
Fan motor
HIGH
MEDIUM
LOW
Compressor
RC
IFM
L1
L2
IFM
X-FRMR
RC
COMP
C
S
R
RC
CFM
CC
L1
L2
L1 T1
L2 T2
R
Y
OFF
COOL
G ON
AUTO
R C
24 V
Goodheart-Willcox Publisher
Figure 9-16. A schematic wiring diagram for a typical split, residential air-conditioning
system.
Copyright Goodheart-Willcox Co., Inc.
A ladder diagram, as shown in Figure 9-15, can be
used to troubleshoot the unit. Assume the unit was set
to operate in the HIGH COOL mode, and the com-
pressor does not operate but the fan does. The prob-
lem can be isolated to the bottom rung of the ladder
diagram, which indicates one of the following issues:
■ The contacts L1-C are not closing.
■ The thermostat might be open.
■ The overload might be open.
■ The compressor or its starting components might
be defective.
■ There is a problem with the interconnecting
wiring in the compressor circuit.
9.4 Basic Split Air-Conditioning
System Wiring Diagrams
Split air-conditioning systems are comprised of two pieces of equipment
called the indoor and outdoor units. This is unlike air-conditioning sys-
tems where all four major system components are enclosed in one cabinet.
Each of the sections of a split air-conditioning system has its own power
supply and control devices. These control devices are powered through
the space thermostat. The space thermostat is also an integral part of an
air-conditioning system. The wiring diagram of a residential split air-con-
ditioning system is shown in Figure 9-16. Each of the components that
make up the system, the thermostat, indoor unit, and outdoor unit, and
their wiring diagrams will be discussed in the following sections.
Goodheart-Willcox Publisher
Figure 9-15. A ladder diagram for a typical window or through-
the-wall air-conditioning unit.
RC
L1 1
L1 3
L1 2
L1
T-STAT
L1 N
RC C
S
R
OL C
Fan motor
HIGH
MEDIUM
LOW
Compressor
RC
IFM
L1
L2
IFM
X-FRMR
RC
COMP
C
S
R
RC
CFM
CC
L1
L2
L1 T1
L2 T2
R
Y
OFF
COOL
G ON
AUTO
R C
24 V
Goodheart-Willcox Publisher
Figure 9-16. A schematic wiring diagram for a typical split, residential air-conditioning
system.