BMC ECON-DB-2, Installation Instructions Manual, Page: 20 / 29

Manual 2100-702D
Page
20 of 29
FIGURE 14
100% Outside Airflow Path
FIGURE 15
Mixed Airflow Path
RETURN AIR
SUPPLY AIR
COOLING COIL
EXHAUST AIR
OUTDOOR AIR
CONDENSER AIR
ELIMINATOR
AIR FILTER
MIST
CONDENSER COIL
MIS-3613
MIS-3612
ELIMINATOR
RETURN AIR
OUTDOOR AIR
EXHAUST AIR
MIST
AIR FILTER
SUPPLY AIR
Economizer Sequence of Operation
Condition – Cool/Dry OA Conditions
• 1 st Stage Cooling closes and sends signal to
JADE ™ control. Since the air temperature outside
is cooler than the preset DRYBULB SET setting,
or is below the ENTH CURVE boundary in the
SETPOINTS menu, the actuator will power the
economizer damper to “economizer” mode as the
indoor blower motor starts. The mixed air sensor
senses a mixture of return air and cool outdoor
air and modulates opening to achieve preset
MAT
SET setting in SETPOINTS menu. Compressor
operation is inhibited (see Figure 14).
• 2 nd Stage Cooling closes and sends a signal to
JADE ™ control, which closes the Y1-O relay to
begin mechanical cooling. The economizer damper
REMAINS OPEN in tandem operation with the
compressor
as long as the OA conditions do not
drop below the preset DRYBULB SET/ENTH
CURVE settings in the SETPOINTS menu (see
Figure 15).
• 3
rd
Stage Cooling (if available) closes and sends a
signal to JADE ™ control, which closes the Y2-O
relay to begin 2 nd stage mechanical cooling. The
economizer damper REMAINS OPEN in tandem
operation with the compressor
as long as the
temperature outside does not drop below the
preset
DRYBULB SET setting in the SETPOINTS
menu (see Figure 15).
Condition – Warm/Humid OA Conditions
• 1 st Stage Cooling closes and sends signal to
JADE ™ control. Since the OA conditions are above
the preset DRYBULB SET/ENTH CURVE setting
in the SETPOINTS menu, the control will simply
close the Y1-O relay to initiate mechanical cooling.
The economizer damper will remain closed or in
a minimum ventilation setting depending upon
occupied status
(see Figure 16).
• 2
nd
Stage Cooling (if available) closes and sends a
signal to JADE ™ control. Since the OA conditions
are still above than the preset DRYBULB SET/
ENTH CURVE setting in the SETPOINTS menu,
the control will simply close the Y2-O relay
to initiate 2
nd stage mechanical cooling. The
economizer damper will remain closed or in a
minimum ventilation setting depending upon
occupied status
(see Figure 16).