Lennox LGM Series Manual page 47

K-Optional Cold Weather Kit (Canada only)
Electric heater is available to automatically control the mini­
mum temperature in the gas burner compartment. Heater
is C.G.A. certified to allow cold weather operation of unit
down to ‐60° F (‐50° C ).
The kit includes the following parts:
1- A heater assembly is installed on the vestibule of the
heating compartment. Included in the box are the fol­
lowing:
a - Electric strip heat (HR6).
b - Thermostat switch (S59) is an auto‐reset SPST N.C.
switch which opens on a temperature drop. The
switch is wired in series with 24v power and the com­
bustion air blower switch. When the temperature
drops below ‐30° F (-35° C) the switch opens and the
gas heat section is de‐energized. The switch auto­
matically resets when the heating compartment tem­
perature reaches -10° F (-12° C).
c - Thermostat switch (S60) is an auto‐reset SPST N.C.
switch which opens on a temperature rise. The
switch is wired in series with HR6. When the temper­
ature rises above 20° F (‐7° C) the switch opens and
the electric heater is de‐energized. The switch auto­
matically resets when the heating compartment tem­
perature reaches ‐10° F (23.3° C).
d -Thermostat switch (S61) is an auto‐reset SPST N.O.
switch which closes on a temperature drop. The
switch is wired in series with HR6. When tempera­
ture drops below 20° F (‐7° C) the switch closes and
electric heater is energized. The switch automatical­
ly opens when heating compartment temperature
reaches 76° F (24° C).
2- K125 heat shutoff relay de-energizes HR6 heaters
when S60 or S61 thermostat switches open. K125 must
be installed in the control section.
3- Wire harness is routed between the heat section com­
ponents and the unit control box. Follow instructions
provided with kit for wire connections.
L-Control Systems
The A55 Unit Controller provides all control function for the
rooftop unit. Default operation requires a standard room
thermostat or direct digital controller (DDC). The A55 can
also control the unit from a zone temperature sensor. The
A55 Unit Controller is a network controller when daisy-
chained to the L Connection
ease of configuration, the A55 can be connected to a PC
with Unit Controller PC software installed.
®
Network Control System. For
M-Indoor Air Quality (CO
The indoor air quality sensor monitors CO
ports the levels to the A55 Unit Controller. The board ad­
justs the economizer dampers according to the CO
The sensor is mounted next to the indoor thermostat or in
the return air duct. Refer to the indoor air quality sensor in­
stallation instructions for proper adjustment. Wiring for the
indoor air quality switch is shown on the temperature con­
trol section (C2) wiring diagram in back of this manual.
N-Drain Pan Overflow Switch S149(optional)
The overflow switch is used to interrupt cooling operation
when excessive condensate collects in the drain pan.
The N.C. overflow switch is connected to the M2 Unit Con­
troller (A55) through DI-3. When the switch opens, the Unit
Controller will shut off the unit. After a five-minute time out,
the Unit Controller will verify the overflow switch position
and restart the unit (if the switch has closed). The Unit Con­
troller has a three-strike counter before the unit locks out.
This means the Unit Controller will allow the overflow switch
to open three times per thermostat demand. If the unit locks
out, a reset of the Unit Controller is required after the switch
has closed to restore unit operation.
O-Smoke Detectors A17 and A64
Photoelectric smoke detectors are a factory installed op­
tion. The smoke detectors can be installed in the supply air
section (A64), return air section (A17), or in both the supply
and return air section. Wiring for the smoke detectors are
shown on the temperature control section (C2) wiring dia­
gram in back of this manual.
P-Factory Installed-Hot Gas Reheat (option­
al)
General
Hot Gas Reheat units provide a dehumidifying mode of op­
eration. These units contain a reheat coil adjacent to and
downstream of the evaporator coil. Reheat coil solenoid
valve, L14, routes hot discharge gas from the compressor
to the reheat coil. Return air pulled across the evaporator
coil is cooled and dehumidified; the reheat coil adds heat to
supply air. See figure 40 for reheat refrigerant routing and
figure 41 for standard cooling refrigerant routing.
Page 47
) Sensor A63
2
levels and re­
2
levels.
2