41
The supply fan motor will cont inue 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--ene rgize d with Y1, indicating AUTO Fan operation,
then the supply fan motor will stop. The W7220 input at
OCC is removed; the outside a ir damper c loses.
If the space temperature continues to rise, the thermos tat will
call for second stage cooling ; ISC terminal Y2 is also
energized. The supply fan motor shifts to MED Speed.
Outside air damper pos itio n will remain in MI N 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 m otor 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 thermos tat will
call for third stage coolin g; IS C terminal Y--3 is also
energized. The supply fan motor shifts to High Speed. The
outs id e air d amper position will shif t to MIN POS H, th ird
stage cooling starts .
As space temperature falls, the thermostat will remove its
call for third stage cooling; ISC terminal Y3 call is
remove d. The supply fan will shift to Medium Speed. T he
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
appropria te changeover command (outdoor dry bulb,
outdoor enthal py, differential dry bul b or differential
enthalpy), a space thermostat call for Stage 1 Cooling
energizes ISC terminals G and Y1; supply fan m otor sta rts
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 operati on, a supply air tempe rature
(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 da mper will re--open t o MIN
POS L setting.
Should 100% outside a ir 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.
Table 14 – W7220 Input/Output without CO
2
Sensor
INPUTS
Ref:
FAN SPD*
OUTPUTS
DEMAND
CONTROLLED
VENTILATION
OUTSIDE AIR
Good to
economize?
Y 1 --- I Y 2 --- I
Mechanical Cooling Stage
Occupancy
OCC Yes OCC No
Y 1 --- O / 1 S T Y 2 --- O / 2 N D Outside Air Damper Position
NO CO
2
SENSOR
No
Off Off Low 0 --- v / O f f 0 --- v / O f f MIN POS L Closed
On Off Low 2 4 --- v / O n 0 --- v / O f f MIN POS L Closed
On On High 2 4 --- v / O n 2 4 --- v / O n MIN POS H Closed
Yes
Off Off Low 0 --- v / O f f 0 --- v / O f f MIN POS L Closed
On Off Low 0 --- v / O f f 0 --- v / O f f
Modulating:
MIN POS L to
F u l l --- O p e n
Modulating:
Closed to
F u l l --- O p e n
On On High
2SP DELAY
{
;
24v/On
0 --- v / O f f * *
Modulating:
MIN POS H to
F u l l --- O p e n
Modulating:
Closed to
F u l l --- O p e n
*
Fan S peed 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 en abled, control can turn on 2
nd
stage of cooling Y2---O after delay if the call for Y2---I h as not
been satisfied.
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