Lennox CHA16, Service Manual

Page: 41 / 86

Page 41
Optional differential enthalpy control may be added to any
economizer to monitor both indoor and outdoor air condi
tions. With differential enthalpy installed, the economizer
selects the lowest of the two enthalpy conditions to satisfy
cooling demand.
1-REMD16M Downflow Economizer
(all units)
The REMD16M economizer is designed for standard
(downflow) use with CHA16 units.In 15 ton and larger units,
the economizer can also be adapted to horizontal dischar
ge.In 12.5 ton and smaller units, the REMD16M cannot be
converted to horizontal discharge and a separate horizontal
economizer (EMDH16M) is used for horizontal applica
tions. Both applications are shown in figure 39.The econo
mizer monitors outdoor air conditions and opens the out
door air dampers to allow 0 to 100 percent outdoor air to be
used for cooling when outdoor humidity and temperature
are acceptable.Damper position continually adjusts to out
door 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 be
comes unacceptable, the outdoor 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 compressor.
FIGURE 37
REMD16M DOWNFLOW ECONOMIZER
ONEPIECE DESIGN FOR
12.5TON AND SMALLER
UNITS
OPTIONAL GED16
GRAVITY EXHAUST DAMPER
Refer to the REMD16M 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 in
teracts with the CHA16 and the control system being used.
FIGURE 38
TYPICAL REMD16M ECONOMIZER
FOR 12.5 TON AND SMALLER UNITS
SHOWN INSTALLED
Unit
REMD16M
REMD16M-185
REMD16M-185
(downflow application)
(horizontal application)
FIGURE 39
Outdoor
Air Dampers
Optional Power
Exhaust Dampers
CHA161853 Unit
Return Air
Air Filters
Gravity
Exhaust Dampers
CHA16-1853 unit
Duct
Outdoor
Air Dampers
Air Filters
Gravity
Exhaust Dampers