Lennox TPA036H4N4 Installation Instructions Manual page 27

compressor demand, it reverts to a lockout mode and
displays the appropriate code. The demand defrost
control detects open sensor or out-of-temperature
sensor range. This fault is detected by allowing the unit
to run for 90 seconds before checking sensor
resistance. If the sensor resistance is not within range
after 90 seconds, the demand defrost control will count
one fault. After five faults, the demand defrost control
will lockout. Code on demand defrost control is
Discharge Sensor Fault and Lockout.
The discharge line sensor, which covers a range of 150°F
(65°C) to 350°F (176°C), is designed to mount on a ½"
refrigerant discharge line.
NOTE − Within a single room thermostat demand, if
5−strikes occur, the demand defrost control will lockout the
unit. demand defrost control 24 volt power R must be
cycled OFF or the TEST pins on demand defrost control
must be shorted between 1 to 2 seconds to reset the
demand defrost control.
Crankcase Heater (HR1) and Crankcase Thermostat
The reference models are equipped with a 70 watt, belly
band type crankcase heater. HR1 prevents liquid from
accumulating in the compressor. HR1 is controlled by a
thermostat located on the liquid line. When liquid line
temperature drops below 50° F the thermostat closes
energizing HR1. The thermostat will open, de−energizing
HR1 once liquid line temperature reaches 70° F .
(S40)
Internal Solenoid (L34)
The internal unloader solenoid controls the two−stage
operation of the compressor by shifting a slide ring
mechanism to open two by−pass ports in the first
compression pocket of the scrolls in the compressor. The
internal solenoid is activated by a 24 volt direct current
solenoid coil. The coil power requires 20VAC. The internal
wires from the solenoid in the compressor are routed to a 2
pin fusite connection on the side of the compressor shell.
The external electrical connection is made to the
compressor with a molded plug assembly. This plug
contains a full wave rectifier that converts 24 volt AC into
24 volt DC power to power the unloader solenoid. Refer to
unit diagram for internal circuitry view of plug).
Outdoor Fan Relay (K10) (G Voltage Only)
Outdoor fan relay K10 is used on all G and voltage units to
energize the outdoor fan B4. The relay is located in the
control box and is a single−pole double−throw relay. See
figure 3. K10 is energized by the indoor thermostat
terminal Y1 (24V). When K10 is energized, a set of N.O.
contacts closes to energize the outdoor fan.
Liquid Line Bi−Flow Filter Drier
The unit is equipped with a large−capacity biflow filter drier
which keeps the system clean and dry. If replacement is
necessary, order another of like design and capacity. The
replacement filter drier must be suitable for use with
HFC−410A refrigerant.
Page 27
TPA*H4 SERIES