Economizer Suitability (SZAHU) - Johnson Controls - Metasys - LIT-12011147 - Software Application - Controller Configuration Tool - 15.0

Controller Tool Help

Johnson Controls
Product name
Controller Configuration Tool
Document type
User Guide
Document number
Revision date

Use this section to select the method of determining when free cooling is available.

Dry Bulb Temperature compares the outdoor air temperature (OA-T) to either a fixed value (ECONSWO-SP) or a return air temperature (RA-T) to determine whether free cooling is available.

The Outdoor Air Enthalpy option calculates enthalpy and compares it to either the fixed economizer enthalpy setpoint (ECON-ENTH-SP) or else the enthalpy calculated using the return air temperature (RA-T) and return are humidity (RA-H) to determine whether free cooling is available.

Enthalpy Switch (BI) adds a binary input designed to be connected to a commercially available enthalpy switch. This type of sensor is typically supplied with package equipment or packaged economizer sections.

Use Outdoor Air to select the desired logic to determine when free cooling is available.
Note: Any economizer strategy that requires the outdoor air temperature or humidity uses a network input by default for these values unless the application included analog inputs for these values. If there are analog inputs for outdoor air temperature or humidity, the network inputs are removed, and the module inputs receive data from the analog inputs.

Dry Bulb Temp Economizer provides free cooling when the outdoor air temperature drops below the economizer switchover setpoint (ECONSWO-SP).

Temperature & Enthalpy Economizer uses the outdoor temperature and humidity and the return temperature and humidity to calculate the enthalpy difference of the two airstreams. It uses free cooling if there is less enthalpy in that air stream as long as the dry bulb temperature is below the economizer switchover setpoint (ECONSWO-SP).

Outdoor Air versus Return Air compares the dry bulb temperature for the outdoor and return air to determine when free cooling is available.