Lennox LCH060H4E

Page 56
FIGURE 21
ECONOMIZER CONTROLS
ECONOMIZER
B7
DAMPER
MOTOR
Outdoor Air Suitability
Sensors or a global input are used to determine outdoor air
suitability for free cooling. See table 28. Once outdoor air
suitability is enabled, the factory-installed discharge air
temperature sensor (RT6) is used to modulate dampers to
55
°F (13°C) discharge air. See the Unit Controller guide to
adjust this setpoint.
NOTE - Free cooling can also be enabled by a message
from an energy management system (EMS). These sys
tems may require additional field-provided sensors; refer to
manufacturers instructions.
Sensors
The appropriate sensors are provided when the economiz
er is factory-installed. When the economizer is field-instal
led, the ODE mode requires additional field-provided sen
sor(s). See table 28. The TEMP mode uses sensors
provided with all units.
DIP Switches
Damper mode is selected using the Unit Controller at unit
start-up. Refer to the Unit Controller guide provided with
each unit. See figure 22 for switch location and figure 23 for
DIP switch settings.
Outdoor Air Suitability LED
A yellow LED which is labeled OAS provides economizer
status. A steady yellow LED indicates that outdoor air is
suitable for free cooling. A flashing yellow OAS light indi
cates the IAQ sensor requires outdoor air. (A flashing yel
low LED can also mean that the economizer dampers are
open to bring in fresh air while a compressor is on.) If the
economizer is already operating, a flashing yellow OAS
light indicates the IAQ sensor requires more outdoor air
than is suitable for free cooling. See figure 22.
Optional Sensor
An optional IAQ sensor (A63) may be used to lower operat
ing costs by controlling outdoor air based on CO
2
level or
room occupancy (also called demand control ventilation or
DCV). Damper minimum position can be set lower than
traditional minimum air requirements; dampers open to
traditional ventilation requirements when CO
2
level reach
es DCV (IAQ) setpoint.
Refer to instructions provided with sensors for installation.
TABLE 28
Mode
DIP
Switch
Outdoor air is suitable for free cooling when:
TEMP (offset) TEMP
Outdoor air temperature (RT17) is less than return air temperature (RT16) minus the offset value (0 to 40°F).
TEMP (setpoint) TEMP
Outdoor air temperature (RT17) is less than the setpoint value (41 to 70°F).
ENTH (differential) ODE Outdoor air enthalpy* (A7) is less than return air enthalpy (A62). Enthalpy setpoint potentiometer is set to DIFF
ENTH (setpoint) ODE Outdoor air enthalpy (A7) is less than enthalpy setpoint potentiometer position A, B, C, or D.
GLOBAL GLO
Global input is energized by (P297-9). This setting is also used for outdoor air damper applications. Global input
also brings on the blower. (This mode is NOT used when OAS signal is provided via network connection. GLO is
only used when a 24VAC signal is used to energize the P297-9 GLO input.)
*Enthalpy includes effects of both temperature and humidity.