Lennox LDT Series Information page 40

I-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
System. For ease of configuration, the A55 can be
connected to a PC with Unit Controller PC software
installed.
J-Smoke Detectors A171, A172, A173
Photoelectric smoke detectors are a factory- and
field-installed 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 panel.
Wiring for the smoke detectors are shown on the
temperature control section (C) wiring diagram in back of
this manual.
K-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. (3.3 Pa) 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.
L-Dirty Filter Switch S27
The dirty filter switch senses static pressure increase
indicating a dirty filter condition. The switch is N.O. and
closes at 1" W.C. (248.6 Pa) 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.
M-LP / Propane Kit
Units require two (one for each gas heat section) natural to
LP/propane kit. The kit includes one gas valve, eleven
burner orifices and three stickers. For more detail refer to
the natural to LP gas changeover kit installation
instructions.
N-Indoor Air Quality (CO
The indoor air quality sensor monitors CO
reports the levels to the A55 Unit Controller. The board
adjusts the economizer dampers according to the CO
levels. The sensor is mounted next to the indoor thermostat
or in the return air duct. Refer to the indoor air quality 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.
®
Network Control
) Sensor A63
2
levels and
2
2
Page 40
O-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
proliferation of mold and other bio-aerosols (bacteria and
viruses) on illuminated surfaces.
Germicidal lamps are NOT intended to be used for removal
of active mold growth. Existing mold growth must be
appropriately removed PRIOR to installation of the
germicidal lamp.
Refer closely to UVC light installation instruction warnings
when servicing units.
P-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
Controller (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 Controller 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.
Q-Indoor Air Quality Sensor
If a sensor fails, use the following procedures to physically
remove the failed sensor from the unit. All units will have
two IAQ sensors installed, one in the return air and the
second one in the supply side. See figure 34. The sensors
are secured to the tray by two screws. The power cable
assembly will need to be detached from the connector
located on the bottom of the sensor as well.
Removing the Sensor
1- Go to Menu > Network Integrations > Wireless Sensor
Network Setup > Wireless Sensor Network.
2- From the Network Nodes list, select the IAQ sensor that
is being replaced.
3- On the Sensor Information Screen, select the Remove
Sensor option at the bottom of the screen..
4- Type in the sensor name that is to be removed and select
Proceed.