modelDownWithOnOff

Information

This example validates Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Staging.Processes.Down.

It shows a process of staging down from stage 2 which requires large chiller 2 to be enabled, to stage 1 which requires small chiller 1 to be enabled and chiller 2 to be disabled.

• In stage 2, the design condenser water pump speed is 0.6 and it requires 2 condenser water pumps. The maximum and minimum chilled water flows are 1.5 m3/s and 1.0 m3/s.
• In stage 1, the design condenser water pump speed is 0.75 and it requires 1 condenser water pump. The maximum and minimum chilled water flows are 1.0 m3/s and 0.5 m3/s.

It demonstrates the process as below:

• Before 120 seconds, the plant is not in the staging process.
• At 120 seconds, the plant starts staging down from stage 2 to stage 1. The operating chiller load is reduced from 2000 to 1000 w (which is lower than 80% of the operating chiller load). It then slowly increases the minimum chilled water flow setpoint from 1 m3/s to both 1.667 m3/s. The setpoint change takes 300 seconds (byPasSetTim) and it ends at about 720 seconds.
• After the new setpoint being achieved, wait 60 seconds (aftByPasSetTim) to 780 seconds, it enables chiller 1 head pressure control (yChiHeaCon[1]=true).
• After 30 seconds (waiTim) to 810 seconds, it starts slowly opening the chiller 1 isolation valve (yChiWatIsoVal[1]). It takes 300 seconds (chaChiWatIsoTim) to fully open the valve, till 1110 seconds.
• At 1110 seconds, the chiller 1 isolation valve is fully open and the chiller becomes enabled (uChi[1]=true).
• After 5 minutes (proOnTim) to 1410 seconds, the chiller 2 becomes disabled (uChi[2]=false, uChiLoa[2]=0).
• After the chiller 2 is disabled and it has no request for chilled water flow, it starts slowly closing the isolation valve of chiller 2. At 1710 seconds, the valve is fully closed.
• At 1710 seconds, the chiller 2 head pressure control becomes disabled (yChiHeaCon[2]=false). It also changes the minimum flow setpoint to the new one for the stage 1, which is 1 m3/s. The staging process is done.

Components

Revisions

• May 30, 2024, by Jianjun Hu:
  First implementation.