_ Installation Instructions
Sequence of Operation
NOTE: For correct wiring to the low voltage terminal board,
see the connection wiring diagram in the economizer's
documentation and page 10 of this manual.
Cooling Mode
When a field supplied two stage thermostat is in the FAN
ON position:
1. The outdoor air dampers will open to the minimum
position with R & G energized.
2. On the thermostat's call for cooling, the thermostat
completes Circuit 1 between thermostat terminals R,
G, O and Y1 for first stage cooling.
If the economizer's outdoor air enthalpy sensor de-
termines that the outdoor air conditions are belowthe
setting for economizer operation, the outdoor air
dampers will modulate open and the return air damp-
ers will modulate closed.
The mixed air sensor at the blower inlet modulates
the economizer dampers to prevent the mixed air
from falling below 56°F (13.3°C). (Mixed air refers to
return air after it combines with outdoor air from the
economizer.) The mixed air sensor modulates the
outdoor air dampers between the full open and mini-
mum outdoor air positions.
If the mixed air is not cold enough to maintain the
conditioned space at the selected temperature, the
thermostat will make ¥2 and call for second stage
cooling by energizing the economizer logic module.
This energizes the Y1 anti-cycle delay timer and
contactor Cl which starts the condenser fan and the
compressor.
If the thermostat is still calling for cooling and the
economizer's outdoor air enthalpy sensor deter-
mines that the outdoor air conditions have risen
above the setting for economizer operation:
Single Package Heat Pumps I
The economizer dampers will close to the mini-
mum position for outdoor air and remain there.
Contactor Cl will remain energized and the com-
pressor will continue to run.
Heating Mode
1.
2.
The outdoor air dampers will open to the minimum
position with R & G energized.
The damper operates at minimum position with R, G
& Y1 energized; in heating operation O is de-ener-
gized. The dampers will not modulate based on the
enthalpy changeover setpoint. Turn to the "D" set-
point and dampers will remain at the minimum posi-
tion setting at high enthalpy conditions for outdoor
air. Turn to the "A" setpoint and the dampers will re-
main at the minimum setting at low enthalpy condi-
tions for outdoor air. This can be checked by putting a
1.2K ohm resistor across terminals O & + and then by
adjusting the setpoint on the enthalpy setpoint
changeover potentiometer. The compressor will run
atthe "D" setting: as the setting is moved to "A" the
compressor will continue to run and the dampers will
remain at minimum position. As the setting is
changed from "A" to "D" the dampers will remain at
minimum position and the compressor will continue
to run.
.
4.
The minimum damper position setting can be set by
adjusting the setting damper position potentiometer.
This can be set so that the dampers will fully close for
a minimum setting if required.
The economizer can be set at a minimum damper
position in heating. The economizer will not modu-
late in the heating mode.
NOTE: For residential applications, it is recommended that
the minimum damper position be set to fully closed position
unless fresh air requirements in the heating mode are nec-
essary.
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