The PCHWP dP (primary chilled water pump differential pressure) Setpoint Reset By Coil Position module resets the building’s chilled water differential pressure setpoint based on the chilled water valve coil positions. The module determines the maximum valve position, the average valve position, and the standard deviation of the valve positions. If the maximum valve position is 100% and the maximum valve position is less than two standard deviations away from the mean, the dP setpoint increases. Conversely, the dP setpoint decreases if the maximum valve position is less than 90%, or the maximum valve position is considered an outlier as determined by being more than two standard deviations from the mean position of all valve inputs. The module is constructed with inputs for four valve coil position inputs. This module is implemented as a control activity.
The System Selection Wizard loads a primary or secondary instance of this module based on the primary and secondary selections made. When you manually add this module (that is, Setpoint/Miscellaneous header right-click menu > New), the name appears as PCHWP dP Setpoint Reset By Coil Position in the palette of the Setpoint/Miscellaneous Module Selection dialog box.
You may need to add more inputs for the specific application. You should define as many inputs as is necessary to get a statistically significant sample size that is representative of the overall population of coil valve positions. If you have more than four coils, add an EWMA block that matches the defined EWMA configuration (use the copy and paste capability) for each additional coil. Then, connect the additional EWMA blocks to the Statistic block.
