Specifications

Page 25
1-REMD24M Downflow Economizer
The REMD24M economizer is designed for standard (down
flow) use with GCS24 units. The REMD24M cannot be con
verted to horizontal discharge. The economizer monitors out
door air conditions and opens the outdoor air dampers to al
low 0 to 100 percent outdoor air to be used for cooling when
outdoor humidity and temperature are acceptable. Damper
position continually adjusts to outdoor conditions. Additional
(second stage) cooling demand is shifted to the first stage
compressor while the dampers remain open to provide first
stage cooling. If outdoor air becomes unacceptable, the out
door air dampers close to a predetermined minimum position
while the compressor cooling circuit cycles as needed. First
stage cooling is shifted back to the first stage compressor and
second stage cooling is directed to the second stage com
pressor.
FIGURE 29
REMD24M DOWNFLOW ECONOMIZER
ONEPIECE DESIGN
OPTIONAL GED16
GRAVITY EXHAUST DAMPER
TYPICAL REMD24M ECONOMIZER
SHOWN INSTALLED
Unit
REMD24M
Refer to the REMD24M installation instruction for specific
installation details. Refer to the operation sequence (in back
of this manual) for detailed economizer operation. Operation
sequence flowcharts also describe how the economizer inter
acts with the GCS24 and the control system being used.
2-Economizer Accessories
a-GED16 Gravity Exhaust Dampers
Optional GED16 gravity exhaust dampers may be
connected to REMD24M economizers. Automatic
exhaust dampers provide positive pressure relief in
return air duct. See figure 29.
b-Warm Up Kit
(units equipped with standard or
electronic thermostat and night
setback function)
An optional warm up kit may be added to the
REMD24M economizer (except GCS24 units using a
Honeywell W7400 control system). The warm up kit
holds the dampers closed during night setback and
morning warm up. When the first thermostat demand of
the day is satisfied, the warm up kit opens the outdoor
dampers to minimum position. The warm up kit installs in
the GCS24 filter access section. The kit plugs into the
unit wiring harness inline between the unit and the econ
omizer. For detailed wiring and operation, refer to the se
quence of operation section of this manual.
If a W973 system is used, the relay kit holds the outdoor
dampers closed during setback. If an electromechanical
thermostat system is used, the relay kit holds the out
door dampers closed during setback, de-energizes the
indoor thermostat and energizes the setback thermo
stat.
c-Differential Enthalpy
(all economizers)
Optional differential enthalpy control may be added to
any economizer to monitor both indoor and outdoor air
conditions. With differential enthalpy installed, the econ
omizer selects the lowest of the two enthalpy conditions
to satisfy cooling demand.
When differential enthalpy is installed, the second en
thalpy sensor is installed in the return air duct while the
original enthalpy sensor remains installed on the outdoor
air dampers.
Refer to the wiring diagram section of this manual for
wiring.
3-Economizer Operation and Controls
(all economizers)
a-Enthalpy Control: Control Setpoint
The key to economizer operation is the enthalpy con
trol. The enthalpy control senses total heat content of
outside air (temperature plus humidity) and uses that
information to control the amount of outside air
brought into the system. When the enthalpy of out
side air drops below the control setpoint and cooling