Carrier WeatherExpert 50LC Installation Instructions Manual page 41

The supply fan motor will continue to run in Low Speed.
W7220 input OCC remains energized; the outside air
damper remains in MIN POS L. If ISC terminal G is also
de- - energized with Y1, indicating AUTO Fan operation,
then the supply fan motor will stop. The W7220 input at
OCC is removed; the outside air damper closes.
If the space temperature continues to rise, the thermostat will
call for second stage cooling; ISC terminal Y2 is also
energized. The supply fan motor shifts to MED Speed.
Outside air damper position will remain in MIN POS L,
second stage cooling starts.
As space temperature falls, the thermostat will remove its
call for second stage cooling; ISC terminal Y2 call is
removed. The supply fan motor shifts back to Low Speed.
The outside air damper remains at MIN POS L and the
ISC board will stop second stage mechanical cooling.
If the space temperature continues to rise, the thermostat will
call for third stage cooling; ISC terminal Y- - 3 is also
energized. The supply fan motor shifts to High Speed. The
outside air damper position will shift to MIN POS H, third
stage cooling starts.
As space temperature falls, the thermostat will remove its
call for third stage cooling; ISC terminal Y3 call is
removed. The supply fan will shift to Medium Speed. The
outside air damper position is repositioned to MIN POS L
and stop third stage mechanical cooling.
When free cooling is available as determined by the
appropriate changeover command (outdoor dry bulb,
INPUTS
DEMAND OUTSIDE AIR
CONTROLLED Good to
VENTILATION economize?
No
NO CO
2
SENSOR
Yes
*
Fan Speed for reference only; this is not an input or output function of the W7220.
{ See Menu ADV SETUP ---> 2SP FAN DELAY for details.
**
See Menu ADV SETUP ---> STG# DLY. With Stage 3 delay enabled, control can turn on 2
been satisfied.
Table 14 – W7220 Input/Output without CO
Ref:
FAN SPD*
Y1--- I Y2--- I
Off Off Low
On Off Low
On On High
Off Off Low
On Off Low
On On High
outdoor enthalpy, differential dry bulb or differential
enthalpy), a space thermostat call for Stage 1 Cooling
energizes ISC terminals G and Y1; supply fan motor starts
and runs in High Speed. The G demand is received at
W7220 input OCC; outside air damper moves to MIN
POS L. The Y1 demand is received at W7220 terminal
Y1- - I. The W7220 economizer control will modulate the
outside air damper open and closed to maintain the unit
cooling supply air temperature at setpoint MAT SET
(default 53_F (12_C)). Compressor will not run.
During free cooling operation, a supply air temperature
(SAT) above MAT SET will cause the outside air damper
to modulate between MIN POS L setpoint and 100%
open. As SAT decreases and approaches setpoint MA LO
SET (default 45_F (7_C)), the outside air damper will
maintain at the MIN POS L setting. With SAT below MA
LO SET, the outside air damper will be closed or at
minimum (see FREEZE POS) When SAT rises to MA LO
SET plus 3_F, the outside air damper will re- - open to MIN
POS L setting.
Should 100% outside air not be capable of satisfying the
space cooling load, space temperature will rise and the
thermostat will call for second stage cooling; ISC terminal
Y2 is also energized. The supply fan motor remains at
High Speed. Outside air damper position will remain at
MIN POS L, starting second stage cooling (Compressor 1
operation). Damper will modulate to maintain SAT at
MAT SET concurrent with Compressor 1 operation.
Sensor
2
OUTPUTS
Mechanical Cooling Stage
Y1--- O/1ST Y2--- O/2ND
0--- v/Off 0--- v/Off
24--- v/On 0--- v/Off
24--- v/On 24--- v/On
0--- v/Off 0--- v/Off
0--- v/Off 0--- v/Off
2SP DELAY ;
{
0--- v/Off**
24v/On
nd
stage of cooling Y2 ---O after delay if the call for Y2 ---I has not
41
Occupancy
OCC Yes OCC No
Outside Air Damper Position
MIN POS L Closed
MIN POS L Closed
MIN POS H Closed
MIN POS L Closed
Modulating: Modulating:
MIN POS L to Closed to
Full--- Open Full--- Open
Modulating: Modulating:
MIN POS H to Closed to
Full--- Open Full--- Open