Issue
How to program a limit block for use in Niagara G3.
Environment
Niagara G3
Cause
Limit are configure using the Reset object in the kitControl palette in the Math folder.
Resolution
Use the Reset object found in the kitControl palette in the Math folder. To use it set the "Input Low Limit" and the "Output Low Limit" to the lowest desired output. Set the "Input High Limit" and "Output High Limit" to the highest desire value.
kitControl-Reset
This component performs a linear “reset” on the inA value. Reset is available in the Math folder of the kitControl palette. Reset operation is defined by the following four slots:
- Input Low Limit — must be less than the Input High Limit
- Input High Limit — must be greater than the Input Low Limit
- Output Low Limit — may (or may not) be greater than the Output High Limit
- Output High Limit — may (or may not) be greater than the Output Low Limit
For example, a Reset object is used to establish a hot water control setpoint, based on the outside air temperature at inA. When the outside air temperature is 0°F, the hot water setpoint is 200°F. When the outside air temperature is 75°F, the hot water setpoint is 100°F. The Reset object is configured as:
- Input Low Limit = 0.0
- Input High Limit = 75.0
- Output Low Limit = 200.0
- Output High Limit = 100.0
Whenever the inA value is beyond the input limits, the output is limited by the corresponding output limit (in this case, 200 at 0°F or below, 100 at 75°F or above). When the input is at an intermediate value, the output scales linearly. For example, when the outside air temperature is at 38.2°F, the Reset output is 149.1°F.
