Lennox 14HPX-024-230-18 - Defrost System (14 HPX-XXX-230-017)

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14HPX SERIES
System Operation (14HPX-XXX-230-017)
UNIT COMPONENTS
IMPORTANT
Some scroll compressor have internal vacuum protector
that will unload scrolls when suction pressure goes below
20 psig. A hissing sound will be heard when the
compressor is running unloaded. Protector will reset when
low pressure in system is raised above 40 psig. DO NOT
REPLACE COMPRESSOR.
The outdoor unit and indoor blower cycle on demand from
the room thermostat. If the thermostat blower switch is in the
ON position, the indoor blower operates continuously.
Bi-Flow Liquid line Filter Drier
The unit is equipped with a large-capacity bi-flow filter drier
which keeps the system clean and dry. If replacement is
necessary, order another of the same design and capacity.
The replacement filter drier must be suitable for use with
HFC-410A refrigerant.
Low Pressure Switch (S87)
The 14HPX is equipped with an auto-reset low pressure
switch which is located on the vapor line. The switch shuts
off the compressor when the vapor pressure falls below the
factory setting. This switch, which is ignored during defrost
operation, closes at pressures at or above 40 + 5 psig (276 +
34 kPa) and opens at 25 + 5 psig (172 + 34 kPa). It is not
adjustable.
Low Pressure Switch Bypass (S41) (Optional)
For use in applications where the heat pump is operated in
outdoor ambient temperatures below 15°F.
 Prevents nuisance trips form the low pressure switch
 Wired in parallel with the low pressure switch
High Pressure Switch (S4)
The 14HPX is equipped with an auto‐reset high pressure
switch (single-pole, single-throw) which is located on the
liquid line. The switch shuts off the compressor when
discharge pressure rises above the factory setting. The
switch is normally closed and is permanently adjusted to trip
(open) at 590 + 15 psig (4068 + 103 kPa).
NOTE -— A Schrader core is under the pressure switches.
Defrost Thermostat (S6)
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 to
start the defrost timing. It also terminates defrost when the
liquid line warms up to 70°F (21°C).
Crankcase Heater (HR1) and Thermostat Switch (S40)
(-60 model only)
All models sizes are equipped with a belly band type
crankcase heater. HR1 prevents liquid from accumulating in
the compressor. The HR1 is controlled by a single pole,
single throw thermostat switch (S40) located on the liquid
line (see figure 2 for location). On all other units, the heater is
on when there is no compressor operation.
Thermal Protection Switch (S173) — Compressor
Mounted
Some 14HPX units are equipped with a compressor
mounted normally closed temperature switch that prevents
compressor damage due to overheating caused by internal
friction. The switch is located on top of the compressor
casing (see figure 1). This switch senses the compressor
casing temperature and opens at 239-257°F (115°C-125°C)
to shut off compressor operation. The auto-reset switch
closes when the compressor casing temperature falls to
151-187°F (66°C-86°C), and the compressor is
re-energized. This single-pole, single-throw (SPST)
bi-metallic switch is wired in series with the 24V Y input
signal to control compressor operation.
Defrost System (14HPX-XXX-230-017)
The defrost system includes a defrost thermostat (S6) and a
defrost control (CMC1).
DEFROST CONTROL (CMC1)
This defrost control includes the combined functions of a
time/temperature defrost control, defrost relay, time delay,
diagnostic LEDs, and a terminal strip for field wiring
connections.
24V TERMINAL
STRIP
CONNECTIONS
DIAGNOSTIC
LEDS
HIGH PRESSURE
SWITCH
TEST
PINS
DEFROST TIMING
PINS (P1)
REVERSING
VALVE
DEFROST
THERMOSTAT (S6)
LOW PRESSURE
SWITCH
COMPRESSOR
DELAY PINS
S4
S87
SERVICE LIGHT
CONNECTIONS
Figure 19. Defrost Control (CMC1)
Defrost Control Timing Pins (P1)
Each timing pin selection provides a different
accumulated compressor run time period for one defrost
cycle. This time period must occur before a defrost cycle
is initiated. The defrost interval can be adjusted to 30 (T1),
60 (T2), or 90 (T3) minutes (see figure 19). The maximum
defrost period is 14 minutes and cannot be adjusted.
NOTE — Defrost control part number is listed near the P1
timing pins.
 Units with defrost control 100269-02: Factory default is
60 minutes
 Units with defrost control 100269-04: Factory default is
90 minutes
If the timing selector jumper is missing, the defrost control
defaults to a 90-minute defrost interval.