Lennox LHT Series Service Manual page 34

F-Gravity Exhaust Dampers
C1DAMP50C dampers (figure 22) are used in downflow
and LAGEDH are used in horizontal air discharge appli-
cations. LAGEDH gravity 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
LHT series units. An exhaust hood is furnished with the
gravity exhaust damper.
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.
LAGED AND LAPEF INSTALLATION
ECONOMIZER
FRESH AIR
HOOD
P18
LAGED GRAVITY
EXHAUST DAMPERS
FIGURE 22
G-C1PWRE10 Power Exhaust Fans
C1PWRE10 power exhaust fans are used in downflow
applications only. C1PWRE10 fans require optional down-
flow gravity exhaust dampers and E1ECON15 econo-
mizers. Power exhaust fans provide exhaust air pressure
relief and also run when return air dampers are closed
and supply air blowers are operating. Figure 22 shows
the location of the power exhaust fans. See installation
instructions for more detail.
H-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 dai-
sy-chained to the L Connection
For ease of configuration, the A55 can be connected to a
PC with Unit Controller PC software installed.
LAPEF
POWER EXHAUST
FAN ASSEMBLY
Network Control System.
®
I-Smoke Detectors A171, A172, A173
Photoelectric smoke detectors are a factory- and field-in-
stalled option. The smoke detectors can be installed in the
supply air section (A172), return air section (A171), or in
both the supply and return air section. Smoke detection
control module (A173) is located below the control pan-
el. Wiring for the smoke detectors are shown on the tem-
perature control section (C) wiring diagram in back of this
manual.
J-Blower Proving Switch S52
The blower proving switch monitors blower operation and
locks out the unit in case of blower failure. The switch is
N.O. and closes at .15" W.C. The switch is mounted on
the middle left corner of the blower support panel. Wiring
for the blower proving switch is shown on the temperature
control section (C) wiring diagram in back of this manual.
K-Dirty Filter Switch S27
The dirty filter switch senses static pressure increase indi-
cating a dirty filter condition. The switch is N.O. and closes
at 1" W.C. The switch is mounted on the top corner of the
economizer. Wiring for the dirty filter switch is shown on
the temperature control section (C) wiring diagram in back
of this manual.
L-Indoor Air Quality (CO2) Sensor A63
The indoor air quality sensor monitors CO2 levels and
reports the levels to the A55 Unit Controller. The board
adjusts the economizer dampers according to the CO2
levels. The sensor is mounted next to the indoor thermo-
stat or in the return air duct. Refer to the indoor air qual-
ity sensor installation instructions for proper adjustment.
Wiring for the indoor air quality switch is shown on the
temperature control section (C) wiring diagram in back of
this manual.
M-Optional UVC Lights
The Healthy Climate germicidal light emits ultraviolet
(UVC) energy that has been proven effective in reducing
microbial life forms (viruses, bacteria, yeasts and molds)
in the air.
UVC germicidal lamps greatly reduce the growth and pro-
liferation of mold and other bio-aerosols (bacteria and vi-
ruses) on illuminated surfaces.
Germicidal lamps are NOT intended to be used for remov-
al of active mold growth. Existing mold growth must be
appropriately removed PRIOR to installation of the germi-
cidal lamp.
Refer closely to UVC light installation instruction warnings
when servicing units.
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