35
Fig. 45 — Integrated Staging Control (ISC) Board
Cooling
In the Cooling Mode, the small and large compressors will be
sequenced to maintain the thermostat temperature setpoint. The
chart below shows the cooling operation based on the follow-
ing conditions.
The outdoor fan and VFD-controlled indoor fan will operate at
low, medium and high speed. The RPM is factory set by the
CFM and static pressure requirements for the unit installed.
Economizer (Optional)
When the Economizer is in Free Cooling Mode and a demand
for cooling exists (Y1 on the thermostat), the Economizer will
modulate the outdoor-air damper to provide a 50°F (10°C) to
55°F (13°C) mixed-air temperature into the zone and run the
indoor-fan at high speed. As mixed-air temperature fluctuates
above 55°F (13°C) or below 50°F (10°C), dampers will be
modulated (open or close) to bring the mixed-air temperature
back within control. Upon more call for cooling (Y2 on the
thermostat), the outdoor-air damper will maintain its current
position, compressor C1 will run, and the outdoor-fan will run
at low speed. If there is further demand for cooling, the out-
door-air damper will maintain its current position, compressor
C2 will run and the outdoor fan will run at medium speed. The
VFD-controlled indoor fan will operate at high speed regard-
less of the cooling demand.
If the increase in cooling capacity causes the mixed-air tem-
perature to drop below 45°F (7°C), the outdoor-air damper will
return to the minimum position. If the mixed-air temperature
continues to fall, the outdoor-air damper will close. Control re-
turns to normal once the mixed-air temperature rises above
48°F (9°C). The power exhaust fans will be energized and de-
energized, if installed, as the outdoor-air damper opens and
closes.
If field-installed accessory CO
2
sensors are connected to the
Economizer, a demand controlled ventilation strategy will be-
gin to operate. As the CO
2
level in the zone increases above the
CO
2
setpoint, the minimum position of the damper will be in-
creased proportionally. As the CO
2
level decreases because of
the increase of fresh air, the outdoor-air damper will be propor-
tionally closed. For economizer operation, there must be a ther-
mostat call for the fan (G). If the unit is occupied and the fan is
on, the damper will operate at minimum position. Otherwise,
the damper will be closed.
DDC
Control
Indoor Fan
“On” Status
IGC
Board
Power
Plug
Phase
Monitor
Relay
Auxilary
Shutdown
Condensate
Overflow
Economizer
Occupancy
Status Code LEDs
Thermostat
DDC
Control
Remote
Shutdown
Smoke
Shutdown
Smoke
Alarm
Low Ambient
Outdoor Fan
Control
Compressors
Reheat
Low-Pressure
Switch
High-Pressure
Switch
Indoor Fan
Motor
Outdoor Fan
Motors
Phase
Monitor
Relay
INPUT OUTPUT
Thermostat
Compressor
C1
Compressor
C2
Indoor
Fan
Speed
Outdoor
Fan Speed
First Stage
Cooling (Y1)
On Off
Low
Low
(700 rpm)
Second Stage
Cooling (Y2)
Off On
Medium
Medium
(800 rpm)
Third Stage
Cooling (Y3)
On On
High
High (1000
rpm)
Summary of Contents for 50LC 14
Page 26: ...26 Fig 34 50LC 14 26 Control Wiring Diagram...
Page 27: ...27 Fig 35 50LC 14 26 RTU Open Control Wiring Diagram...
Page 28: ...28 Fig 36 50LC 14 20 208 230V 3 Phase Power Wiring Diagram...
Page 29: ...29 Fig 37 50LC 24 26 208 230V 3 Phase Power Wiring Diagram...
Page 30: ...30 Fig 38 50LC 14 26 460V 575V 3 Phase Power Wiring Diagram...