Page 12
DEFROST CONTROL BOARD
FIGURE 13
24V
TERMINAL
STRIP
HIGH PRESSURE
SWITCH
TERMINALS
S4
S5
PRESSURE SWITCH
WIRING CONNECTIONS
High
Pressure
Switch
(Factory−wired)
OPTIONAL
PRESSURE
SWITCH
TERMINALS
(Remove factory−
installed jumper
to install
pressure switch.)
Optional
Pressure
Switch
(Field−provided
and installed −−
jumper removed)
AMBIENT
THERMISTER
TERMINALS
SERVICE
LIGHT
TERMINALS
DIAGNOSTIC
LEDs
DEFROST
INTERVAL
TIMING PINS
CC
Y
IV−REFRIGERANT SYSTEM
A−Plumbing
An expansion/check valve is used in parallel in the liquid
line. The check valve is closed when the unit is in heating
mode to force refrigerant through the expansion valve.
The check valve is open when the unit is in cooling mode.
Field refrigerant piping consists of liquid and vapor lines
from the outdoor unit (sweat connections). Use Lennox
L10 (flare) or L15 (sweat) series line sets as shown in table
7 or field fabricated refrigerant lines. Refer to the piping
section of the Lennox Unit Information Service Manual for
proper size, type and application of field-fabricated lines.
If refrigerant tubes are routed through a wall, seal and iso-
late the opening so vibration is not transmitted to the build-
ing.
NOTE − Line length should be no greater than 50 feet (15.2
m). Select line set diameters from table 1 to ensure oil re-
turn to compressor.
TABLE 7
REFRIGERANT LINE SET KITS
HP27
UNIT
LIQUID
VAPOR
L10
LINE
LINE
LINE SETS
−024
−030
3/8 in.
3/4 in.
L10−41
(9.5 mm) (19.1 mm)
20 ft. − 50 ft.
(6.1 m−15.2 m)
−042
3/8 in.
(9.5 mm)
7/8 in.
(22.2 mm)
L10−65
30 ft. − 50 ft.
(9.1 m − 15.2 m)
L15
LINE SETS
L15−41
15 ft. − 50 ft.
(4.5 m−15.2 m)
L15−65
15 ft. − 50 ft.
(4.5 m−15.2 m)
−036
Separate discharge and suction service ports are pro-
vided at the compressor for connection of gauge manifold
during charging procedure. Figure 14 and 15 show HP27
gauge manifold connections.
