11
Fig. 14 - Enthalpy Control Sensor,
Dimensions and DIP Switch Location
Table 9 - Enthalpy Control Sensor
Wiring Terminations
a
Table 10 - Enthalpy Control Sensor DIP Switch
Terminal
Type
Description
Nbr
Label
1
S─BUS
S─BUS
S─Bus Communications
(Enthalpy Control Sensor Bus)
2
S─BUS
S─BUS
S─Bus Communications
(Enthalpy Control Sensor Bus)
Use
DIP Switch Positions for Switches 1,2, & 3
1
2
3
DA
a
OFF
ON
OFF
RA
b
ON
OFF
OFF
OA
c
OFF
OFF
OFF
a DA = Discharge Air or Supply Sensor
b RA = Return Air
c OA = Outside Air
OPERATION
Cooling, Unit with EconoMi$er X
For Occupied mode operation of EconoMi$er X, here 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 con-
trol in Unoccupied mode.
During Occupied mode operation, indoor fan operation will be accom-
panied by economizer dampers moving to Minimum Position setpoint
for ventilation. If indoor fan is off, dampers will close. During Unoc-
cupied 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 change-
over command (dry bulb, outdoor enthalpy, differential dry bulb or dif
-
ferential 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
o
F. Compressor
will not run.
During free cooling operation, a supply air temperature (SAT) above
50
o
F will cause the dampers to modulate between Minimum Position
setpoint and 100% open. With SAT from 50
o
F to 45
o
F, the dampers will
maintain at the Minimum Position setting. With SAT below 45
o
F, the
outside air dampers will be closed. When SAT rises to 48
o
F, the damp
-
ers will re-open to Minimum Position setting.
Should 100% outside air not be capable of satisfying the space tempera-
ture, 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
o
F concurrent with Compressor 1 operation.
The Low Ambient Lockout Thermostat will block compressor operation
with economizer operation below 42
o
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 run-
ning 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-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 ac-
companied 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$er X
control, a Demand controlled Ventilation strategy will operate automati-
cally. As the CO
2
level in the space increases above the setpoint (on
the EconoMi$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.
