Issue
When air temperature falls to 30 degrees F, the output values calculated by the Enthalpy object are incorrect as compared to performing manual calculation verification or humidity measurement
Environment
IA Series MNL-800 controller
WorkPlace Tech Tool (any version)
Cause
The Enthalpy object limits the allowed range of its input values so as to maintain the resolution of the values it calculates. These range limits are set based on the temperatures typically encountered when calculating enthalpy for mixed air, return air and supply air needs in air handlers.
Resolution
The following limits are used when processing the Enthalpy object inputs:
- Dry Bulb Temperature: 32 to 120 Degrees F (0 to 48.9 Degrees C)
- Dewpoint Temperature: 32 to 120 Degrees F (0 to 48.9 Degrees C)
- Relative Humidity: 1 to 100%
- Barometric Pressure: 19.94 to 39.79 in-Hg (506.5 to 1010.7 mm-Hg)
Input values outside the ranges listed will be processed as if they were clamped to the listed limit. For example if the air temperature (dry bulb) was 26 degrees F, it will be processed as if the temperature were 32 degrees F.