Page 43
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 outdoor sensible
temperature is less than return air sensible temperature, out-
door air is used for cooling. This may be supplementedby me-
chanical cooling to meet comfort demands. This application
does not require additional optional sensors.
2-“ODE” MODE (OUTDOOR ENTHALPY)
The “ODE” or outdoor enthalpy mode requires a field or
factory provided and installed Honeywell C7400 enthalpy
sensor (16K96). The sensor monitors outdoor air tem-
perature and humidity (enthalpy). When outdoor air en-
thalpy is below the enthalpy control setpoint, the economizer
modulates to allow outdoor air for free cooling. See
table 25 for enthalpy setpoints.
ENTHALPY CONTROL SETPOINTS
CONTROL
SETTING
ENTHALPY CONTROL SETPOINT
AT 50% RELATIVE HUMIDITY
APPROXIMATE °F (°C)
A
B
C
D
73 (23)
70 (21)
67 (19)
63 (17)
TABLE 25
“DIF” MODE ONLY
When the enthalpy setpoint is in the “DIF” position, the
economizer board will compare outdoor air enthalpy to re-
turn air enthalpy. If outdoor air enthalpy is lower than re-
turn air enthalpy, dampers will allow use of outdoor air. If
return air enthalpy is lower than outdoor air enthalpy,
dampers will modulate to minimum position.
3-“DIF” MODE (DIFFERENTIAL ENTHALPY)
The “DIF” or differential enthalpy mode requires two field or
factory 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 re-
turn 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 regardless of whether an energy management
system is used.
NOTE - All economizer modes of operation will mod-
ulate dampers to 55_F (13_C) supply air.
F-LAGED03/07 and LAGEDH10/15
Gravity Exhaust Dampers
LAGED003/07 and LAGEDH10/15 dampers are used
withLGA/LCAseries units. LAGED dampers are used in
downflow and LAGEDH are used in horizontal air dis-
charge applications. LAGEDH gravity exhaust dampers
are installed in the return air duct.
Gravity exhaust dampers allow exhaust air to be discharged
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.
FIGURE 33
LAPEF INSTALLATION
LAPEF
POWER EXHAUST
FAN ASSEMBLY
ECONOMIZER
FRESH AIR
HOOD
G-LAPEF03/07 Power Exhaust Fan
LAPEF03/07 power exhaust fan assembly is used with LGA /
LCA series units. LAPEF (requires optional LAREMD econo-
mizers) is used in downflow applications only. The power ex-
haust fan provides exhaust air pressure relief and also runs
when return air dampersare closed and the supply air blow-
er is operating. Figure 33 shows location of the LAPEF. See
installation instructions for more detail.
H-Optional Cold Weather Kit (Canada only)
Electric heater is available to automatically control the
minimum temperature in the gas burner compartment.
Heater is U.L. and U.L.C. certified to allow cold weather
operation of unit down to -60° F (-50° C ).
The kit includes the following parts:
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