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.
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. |
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.