Specifications

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 cooling is

available. Note: The 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.

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.

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