Lennox LGT Series Unit Information page 41

H-Economizer (all units) (Field or Factory Installed)
The optional E1ECON15 economizer can be used with
downflow and horizontal air discharge applications. See
figure 33. The economizer uses outdoor air for free cool-
ing when outdoor temperature and/or humidity is suitable.
The economizer is controlled by the A55 Unit Controller.
Free Cooling Mode
The Unit Controller will allow free cooling in one of five
modes. Each mode uses different combinations of sen-
sors to determine outdoor air suitability. See table 13
for modes. Temperature offset is the default free cooling
mode.
NOTE - All free cooling modes of operation will modulate
dampers to 55F (13C) supply / discharge air.
Unit Controller Settings
On early versions, switches are located on the Unit Con-
troller to adjust settings. On newer versions, the display
and keypad on the Unit Controller are used to navigate
through menus to adjust settings. Some versions require
a configuration ID be entered to enable the economiz-
er. Refer to economizer installation instructions and Unit
Controller installation and application manuals.
I-Gravity Exhaust Dampers
LAGEDH03/15 dampers (figure 31) are used in downflow
and horizontal air discharge applications. Horizontal gravi-
ty exhaust dampers are installed in the return air plenum .
The dampers must be used any time an economizer or
power exhaust fans are applied to LGT units.
Gravity exhaust dampers allow exhaust air to be dis-
charged 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
installation instructions for more detail.
J-LAPEF Power Exhaust Fans
Power exhaust fans are used in downflow applications
only. Fan requires optional down flow gravity exhaust
dampers and LAREMD economizer. Power exhaust fans
provide exhaust air pressure relief and also run when re-
turn air dampers are closed and supply air blowers are op-
erating. Figure 32 shows the location of the LAPEF. See
installation instructions for more detail.
Page 41
GED AND PEF
PEF POWER
EXHAUST FAN ASSEMBLY
(ORDERED SEPARATELY)
GED GRAVITY
EXHAUST DAMPERS
FIGURE 31
POWER EXHAUST FAN
P18/P24 RETURN AIR
OPENING
POWER EXHAUST
FAN ASSEMBLY
FIGURE 32