Lennox LHT Series Service Manual page 33

C1DAMP10 MANUAL OUTDOOR AIR DAMPER
E1DAMP20 MOTORIZED OUTDOOR AIR DAMPER
FILTER BRACKET SIDE VIEW
FIGURE 21
D-Supply and Return Diffusers
Optional flush mount diffuser/return FD11 and extended
mount diffuser/return RTD11 are available for use with all
LHT units. Refer to manufacturer's instructions included
with transition for detailed installation procedures.
E-E1ECON15C-2 Standard and E1ECON17C-1 High
Performance Economizer (Field or Factory Installed)
The optional economizer can be used with downflow and
horizontal air discharge applications. The economizer
uses outdoor air for free cooling when temperature and/
or humidity is suitable. An economizer hood is furnished
with the economizer.
HOOD TOP SEAL
HOOD TOP
FILTER
NOTE - Gravity exhaust dampers are required with power
exhaust.
The economizer is controlled by the A55 Unit Controller.
The economizer will operate in one of four modes. Each
mode requires a different A55 Unit Controller DIP switch
setting. Each mode also requires different sensors. The
following is a brief description. See economizer installa-
tion instruction for more detail.
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 out-
door sensible temperature is less than return air sensible
temperature, outdoor air is used for cooling. This may be
supplemented by mechanical cooling to meet comfort de-
mands. This application does not require additional op-
tional sensors.
2-"ODE" MODE (OUTDOOR ENTHALPY)
The "ODE" or outdoor enthalpy mode requires a field-pro-
vided and -installed Honeywell C7400 enthalpy sensor
(16K96). The sensor monitors outdoor air temperature
and humidity (enthalpy). When outdoor air enthalpy is be-
low the enthalpy control setpoint, the economizer modu-
lates to allow outdoor air for free cooling.
3-"DIF" MODE (DIFFERENTIAL ENTHALPY)
The "DIF" or differential enthalpy mode requires two
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
return 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 modulate
dampers to 55 F supply air.
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