Page 4
Revised 05−2009
TPA*S4
I − UNIT COMPONENTS
Unit components are illustrated in figure 1.
TPA*S4 UNIT COMPONENTS
FIGURE 1
control box
service valves
compressor
reversing valve
condenser fan
drier
muffler
FIGURE 2
CAPACITOR
(C1)
COMPRESSOR
CONTACTOR
(K1)
TPA*S4 UNIT CONTROL BOX
GROUNDING
LUG
DEFROST
CONTROL
(CMC1)
DANGER
Electric Shock Hazard.
May cause injury or death.
Disconnect all remote electrical power
supplies before opening unit panel. Unit
may have multiple power supplies.
A − Control Box (Figure 2)
TPA*S4 units are not equipped with a 24V transformer. All
24 VAC controls are powered by the indoor unit. Refer to
wiring diagram.
Electrical openings are provided under the control box
cover. Field thermostat wiring is made to a 24V terminal
strip located on the defrost control board located in the
control box. See figure 3.
24V THERMOSTAT TERMINAL STRIP
FIGURE 3
W1
C
L
R
O
Y1
1 − Compressor Contactor K1
The compressor is energized by a contactor located in the
control box. See figure 2. Three−pole contactors are used
in TPA*S4 series units. K1 is energized through the
control board by the indoor thermostat terminal Y1 (24V)
when thermostat demand is present.
2 − Capacitor C1
All units use single−phase PSC outdoor fan motors which
require a run capacitor. Ratings for capacitor will be on
fan motor nameplate. C1 aids in the start up of outdoor
fan B4.
3 − Defrost System
The TPA036S4 defrost system includes two components:
a defrost thermostat and a defrost control.
Defrost Thermostat
The defrost thermostat is located on the liquid line between
the check/expansion valve and the distributor. When
defrost thermostat senses 42°F (5.5°C) or cooler, the
thermostat contacts close and send a signal to the defrost
control board to start the defrost timing. It also terminates
defrost when the liquid line warms up to 70°F (21°C).
