The chiller plant load uses a Capacity Calculation based on % Full Loads Amps or Actual Amps. When % Full Load Amps is selected, a Setpoint/Miscellaneous module Capacity Calculation Pct FLA module receives percent load inputs from each chiller. The inputs are used with the device operating capacity to calculate each device load (in tons), and then added to the other devices running to determine the current chiller plant capacity. This current chiller plant capacity is compared with the total chiller plant capacity to determine the percentage of total chiller plant available.
When Actual Amps is selected, a Setpoint/Miscellaneous module Capacity Calculation Amp for Actual Amp selection, receive signals from current transducers from each chiller. The module adds the amperage of all the current devices. The percent load is determined as a percentage of the total Actual Amperage of the chiller plant to the total chiller plant available.
This method of load calculation is less expensive to implement than the Building Load method. One disadvantage of this method is that the application uses a secondary data source (electric load), as compared to the Building Load sensor, which uses a primary data source (heat flow).