Laged(H) Gravity Exhaust Dampers; Lapef Power Exhaust Fans; Optional Cold Weather Kit - Lennox LGA Series Unit Information

1−
TMP" MODE (SENSIBLE TEMPERATURE)
In the TMP" mode, the IMC uses input from the factory
installed RT6 Supply Air Sensor, RT16 Return Air Sensor, and
RT17 Outdoor Air Sensor to determine suitability of outside air
and economizer damper operation. When outdoor sensible
temperature is less than return air sensible temperature, out-
door air is used for cooling. This may be supplemented by me-
chanical cooling to meet comfort demands. This application
does not require additional optional sensors.
2−
ODE" MODE (OUTDOOR ENTHALPY)
The ODE" or outdoor enthalpy mode requires a factory or
field−provided and −installed Honeywell C7400 enthalpy
sensor (16K96). The sensor monitors outdoor air tem-
perature and humidity (enthalpy). When outdoor air en-
thalpy is below the enthalpy control setpoint, the economizer
modulates to allow outdoor air for free cooling.
3−
DIF" MODE (DIFFERENTIAL ENTHALPY)
The DIF" or differential enthalpy mode requires two factory
or field−provided and −installed Honeywell C7400 enthalpy
sensors (16K97). One sensor is installed in the outside air
opening and the other sensor is installed in the return air
opening. When the outdoor air enthalpy is below the re-
turn air enthalpy, the economizer opens to bring in out-
door air for free cooling.
4−
GLO" MODE (GLOBAL)
Global Mode − The GLO" or global mode is used with an
energy management system which includes a global con-
trol feature. Global control is used when multiple units (in
one location) respond to a single outdoor air sensor. Each
energy management system uses a specific type of out-
door sensor which is installed and wired by the controls
contractor.
Motorized Outdoor Air Damper − The GLO" mode is also
used when a motorized outdoor air damper is installed in
the system.
NOTE − All economizer modes of operation will mod-
ulate dampers to 55_F (13_C) supply air.
F−LAGED(H)30/36 Gravity Exhaust Dampers
LAGED(H)30/36 dampers are used with LGA/LGC/LCA/
LCC series units. LAGED dampers are used in downflow
and LAGEDH are used in horizontal air discharge ap-
plications. LAGED gravity exhaust dampers are installed
in the return air cokpartment of the unit (see figure 38). The
dampers must be used any time power exhaust fans are ap-
plied to LGA/LGC/LCA/LCC series units and are optional
with an economizer.
LAGEDH horizontal gravity exhaust dampers are installed in
the return air duct. Gravity exhaust dampers allow exhaust air
to be discharged from the system when an economizer and/or
power exhaust is operating. Gravity exhaust dampers also
prevent outdoor air infiltration during unit off cycle. See installa-
tion instructions for more detail.
LAGED AND LAPEF
INSTALLATION
ECONOMIZER
FRESH AIR
HOOD
LAGED GRAVITY
EXHAUST DAMPERS
G−LAPEF30/36 Power Exhaust Fans
LAPEF30/36 power exhaust fans are used with LGA/LGC/
LCA/LCC series units. LAPEF (requires optional down-flow
gravity exhaust dampers and LAREMD economizer) is used in
downflow applications only. Power exhaust fans provide ex-
haust air pressure relief and run when return air dampers
are closed and supply air blowers are operating. Figure 38
shows location of the LAPEF. See installation instructions
for more detail.
H−Optional Cold Weather Kit (Canada only)
Electric heater is available to automatically control the
minimum temperature in the gas burner compartment.
Heater is C.G.A. certified to allow cold weather opera-
tion of unit down to -60°F (-50°C ).
The kit includes the following parts:
1− Transformer (T20) is a 600V to 120/240V stepdown trans-
former mounted in the blower compartment.
2− T20 has two in line fuses (F20), one on each leg of the trans-
former. Both are rated at 15 amps.
3− The strip heater (HR6) is located as close as possible to the
gas valve. It is wired in series with T20. The strip heater is
rated at 500 Watts.
4− A thermostat mounting box is installed on the vesti-
bule of the heating compartment. Included in the box
are the following thermostat switches:
a − 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
combustion air blower switch. When the temperature
drops below -20°F (−28.9°C) the switch opens and the
gas heat section is de-energized. The switch automati-
cally resets when the heating compartment tempera-
ture reaches 10°F (-12.2°C).
Page 62
LAPEF
POWER EXHAUST
FAN ASSEMBLY
FIGURE 38