The Economizer Controller accepts inputs for 1-, 2- and 3-stage cooling inputs, and reroutes to the RTU through the relay connection Y1, Y2 and AUX1/AUX2.

The operation of the cooling stages is determined by the availability of Free Cooling provided by the economizer operation mode. See Cooling Stage I/O Logic tables.

Based on the use of Free Cooling, the operating modes are as follows:

  • Y1 is Stage 1 Cooling Demand.
  • Y2 is Stage 2 Cooling Demand.
  • Y3 is Stage 3 Cooling Demand.
  • Free Cooling is always the first cooling stage.
  • Cooling Stage 1 call from the Commercial Thermostat (Y1) energizes the Y1 input to the Economizer Controller.
  • Cooling Stage 2 call from the Commercial Thermostat (Y2) energizes the Y2 input to the Economizer Controller.
  • Cooling Stage 3 call from the Commercial Thermostat energizes the AUX1/AUX2 input to the Economizer Controller.
1- and 2-Stage Cooling I/O Logic

Economizer condition met

Y1

Y2

Cooling Stage 1

Cooling Stage 2

No

On

On

On

On

No

On

Off

On

Off

No

Off

Off

Off

Off

Yes

On

On

On1)

On/Off2)

Yes

On

Off

Off

Off

Yes

Off

Off

Off

Off

1

If Y2-Input is called too, the controller increases fan speed to Speed High and starts fan delay (2FAN DLY) time. After the delay time runs out, the controller starts Y1-Output.

2

If Y1O is ON for more than a set time (15 minutes by default, changeable via Parameter '3STG3 DLY)', Y2I cooling demand remains ON, and OAT is lower than MAT setpoint (3MAT SET), then Relay 2 is OFF to disable Cooling Stage 2. If the OAT is higher than the MAT setpoint, then Relay 2 energizes to allow Y2 pass-through to enable Cooling Stage 2.

1-, 2- and 3-Stage Cooling I/O Logic

Economizer condition met

Y1

Y2

Y3

Cooling Stage 1

Cooling Stage 2

Cooling Stage 3

No

On

On

On

On

On

On

No

On

On

Off

On

On

Off

No

On

Off

Off

On

Off

Off

No

Off

Off

Off

Off

Off

Off

Yes

On

On

On

On1)

On2)

On/Off4)

Yes

On

On

Off

On1)

On/Off3)

Off

Yes

On

Off

Off

Off

Off

Off

Yes

Off

Off

Off

Off

Off

Off

1

If Y2-Input is called too, the controller increases fan speed to Speed High and starts fan delay (2FAN DLY) time. After the delay time runs out, the controller starts Y1-Output.

2

If Y3-Input is called too, the controller increases fan speed to Speed High and starts fan delay (2FAN DLY) time. After the delay time runs out, the controller starts Y2-Output.

3

If Y1O is ON for more than a set time (15 minutes by default, changeable via Parameter '3STG3 DLY)', Y2I cooling demand remains ON, and OAT is lower than MAT setpoint (3MAT SET), then Relay 2 is OFF to disable Cooling Stage 2. If the OAT is higher than the MAT setpoint, then Relay 2 energizes to allow Y2 pass-through to enable Cooling Stage 2.

4

If Y2O is ON for more than a set time (15 minutes by default, changeable via Parameter '3STG3 DLY)', Y3I cooling demand remains ON, and OAT is lower than MAT setpoint (3MAT SET), then Relay 3 is OFF to disable Cooling Stage 3. If the OAT is higher than the MAT setpoint, then Relay 3 energizes to allow Y3 pass-through to enable Cooling Stage 3.

The Economizer Controller tolerates thermostat wiring mismatch (e.g. Thermostat Y1 -> Economizer Y2-In, Thermostat Y2 -> Economizer Y1-In). It doesn't recognize if signal comes from Y1-In or Y2-In but calculates the number of received signals and decides the number of cooling/heating demands based on the received signal number. The handling logic is Stage =Y1I + Y2I + Y3I.