3.
Call for Second Stage of Cooling (Y2)
A. Economizer Unavailable (warm outdoor air).
Compressor 2 is commanded on without delay.
B. Economizer Available (free cooling). Compressor
1 is commanded on without delay. The controller
tries to maintain a discharge air temperature of
53ºF ± 5 by modulating the outside air damper
position. Compressor 2 is not activated in the
economizer mode.
4.
Call for Heat
A. Standard Air Conditioner with electric or gas heat.
(W1 & W2)
a.
The Thermostat controls the stages of heating
directly.
b.
If the control detects that the supply fan is on
(through its "G" input), then the control will
open the damper to minimum position.
c.
If the discharge air temperature drops below
48ºF, then the control will override the
minimum position setting and will modulate
the outdoor damper closed.
B. Heat Pump Operation (B)
a.
The "B" signal from the Thermostat allows
operation of the compressors to provide
heating without delay.
b
If the control detects that the supply fan is on
(through its "G" input), then the control can
open the damper to minimum position.
c.
If the discharge air temperature drops below
48ºF, then the control will override the
minimum position setting and will modulate
the outdoor damper closed.
5.
Low Ambient Compressor Lockout – None present.
6
F. The controller compares the CO
2
sensor input to
the setpoint setting to determine the damper
minimum position.
a.
If the actual CO
2
level is below the setpoint,
then the damper minimum position is
determined by the damper minimum position
potentiometer setting.
b.
If the actual CO
2
level rises above the
setpoint, then the damper minimum position is
overridden proportionally more open.
c.
If the discharge air temperature drops below
48°F (Freeze Protect Mode), the DCV input
will be overridden and the damper may not
open.
G. Compatible CO
2
sensors will have a 2-10Vdc
output for a 0-1500 ppm CO
2
input.
H. Ensure proper polarity of the sensor wires when
connecting to the economizer controller. Incorrect
polarity negates the sensor signal.
5.
Economizer Setpoint
A. Only the coolest, driest outside air is used for
economizer operation when the potentiometer is
on setting "D". For greatest energy savings, the
potentiometer is on setting "A".
B. Adjustment range is A, B, C, or D
a.
Setting "A" = 73F db or 27 Btu/lbm @ 50% RH
b.
Setting "B" = 70F db or 25 Btu/lbm @ 50% RH
c.
Setting "C" = 67F db or 23 Btu/lbm @ 50% RH
d.
Setting "D" = 63F db or 22 Btu/lbm @ 50% RH
C. Economizer Setpoint potentiometer can be
adjusted at any time.
D. The controller compares the enthalpy sensor input
with the economizer setpoint to determine if free
cooling is available.
a.
Single enthalpy strategy: If outdoor air
enthalpy is lower than the setpoint, then free
c o o l i n g i s a v a i l a b l e . N o t e : T h e
factory-installed 620-ohm resistor must be in
place across terminals SR and SR+.
b.
Dual enthalpy strategy: If outdoor air enthalpy
is lower than return air enthalpy, then free
cooling is available.
1.
Note: If using dual enthalpy, the Economizer
Setpoint must be at the "D" setting.
2.
The factory-installed 620-ohm jumper must
be removed to install the dual enthalpy
upgrade kit.
NOR MAL OP ER A TION
1.
Fan Only (G)
A. Damper will go to minimum position (in 90
seconds or less) whenever the "G" (supply fan)
signal is present.
B. When "G" signal is removed, the outside air
damper closes against blade seals for tight shutoff
of outside air.
C. If the discharge air temperature drops below 48ºF,
then the control will override the minimum position
setting and will modulate the outside air damper
closed.
2.
Call for First Stage of Cooling (Y1)
A. Economizer Unavailable (warm outdoor air).
Compressor 1 is commanded on without delay.
B. Economizer Available (free cooling). The
controller tries to maintain a discharge air
temperature of 53ºF ± 5 by modulating the outside
air damper position.
FIGURE 7