10
OPERATION
Cooling, Unit With EconoMi$er X
For Occupied mode operation of EconoMi$er X, there
must be a 24-v signal at terminals R and OCC (provided
through PL6-3 from the unit’s IFC coil). Removing the
signal at OCC places the EconoMi$er X control in
Unoccupied mode.
During Occupied mode operation, indoor fan operation
will be accompanied by economizer dampers moving to
Minimum Position setpoint for ventilation. If indoor fan is
off, dampers will close. During Unoccupied mode
operation, dampers will remain closed unless a Cooling
(by free cooling) or DCV demand is received.
When free cooling using outside air is not available, the
unit cooling sequence will be controlled directly by the
space thermostat. Outside air damper position will be
closed or Minimum Position as determined by occupancy
mode and fan signal.
When free cooling is available as determined by the
appropriate changeover command (dry bulb, outdoor
enthalpy, differential dry bulb or differential enthalpy), a
call for cooling (Y1 closes at the thermostat) will cause
the economizer control to modulate the dampers open and
closed to maintain the unit supply air temperature at 50 to
55
_
F. Compressor will not run.
During free cooling operation, a supply air temperature
(SAT) above 50
_
F will cause the dampers to modulate
between Minimum Position setpoint and 100% open. With
SAT from 50
_
F to 45
_
F, the dampers will maintain at the
Minimum Position setting. With SAT below 45
_
F, the
outside air dampers will be closed. When SAT rises to 48
_
F,
the dampers will re-open to Minimum Position setting.
Should 100% outside air not be capable of satisfying the
space temperature, space temperature will rise until Y2 is
closed. The economizer control will call for compressor
operation. Dampers will modulate to maintain SAT at 50
to 55
_
F concurrent with Compressor 1 operation. The
Low Ambient Lockout Thermostat will block compressor
operation with economizer operation below 42
_
F outside
air temperature.
When space temperature demand is satisfied (thermostat Y1
opens), the dampers will return to Minimum Damper
position if indoor fan is running or fully closed if fan is off.
If accessory power exhaust is installed, the power exhaust
fan motors will be energized by the economizer control as
the dampers open above the EXH1 SET setpoint and will
be de--energized as the dampers close below the EXH1
SET setpoint.
Damper movement from full closed to full open (or vice
versa) will take between 1-1/2 and 2-1/2 minutes.
Heating With EconoMi$er X
During Occupied mode operation, indoor fan operation
will be accompanied by economizer dampers moving to
Minimum Position setpoint for ventilation. If indoor fan is
off, dampers will close. During Unoccupied mode
operation, dampers will remain closed unless a DCV
demand is received.
When the room temperature calls for heat (W1 closes), the
heating controls are energized.
Demand Controlled Ventilation
If a field-installed CO
2
sensor is connected to the
EconoMi$er X control, a Demand Controlled Ventilation
strategy will operate automatically. As the CO
2
level in
the space increases above the setpoint (on the EconoMi$er
X controller), the minimum position of the dampers will
be increased proportionally, until the Maximum
Ventilation setting is reached. As the space CO
2
level
decreases because of the increase in fresh air, the
outdoor-damper will follow the higher demand condition
from the DCV mode or from the free-cooling mode.
DCV operation is available in Occupied and Unoccupied
periods with EconoMi$er X. However, a control
modification will be required on the 48TC units to
implement the Unoccupied period function.
Table 8 – Damper Position Control, 2--Speed Fan Motor, Economizer Cooling Not Available
INPUT
OCC
0---V
24---V
24---V
24---V
24---V
Y1
0---V
0---V
24---V
24---V
0---V
Y2
0---V
0---V
0---V
24---V
0---V
W1
0---V
0---V
0---V
0---V
24---V
SUPPLY FAN
MOTOR SPEED
OFF
LOW
LOW
HIGH
HIGH
DAMPER POSITION
NO CO2 SENSOR
CLOSED
MIN POS
MIN POS
MIN POS
MIN POS
W/CO2 SENSOR
CLOSED
FROM
VENTMIN L
TO
VENTMAX L
FROM
VENTMIN L
TO
VENTMAX L
FROM
VENTMIN H
TO
VENTMAX H
FROM
VENTMIN H
TO
VENTMAX H
LLECO
N
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01
S
I
