Chilled Water Systems
Lesson 4.3
What Is a Chilled Water System
The mirror image of the hot water system. The chiller replaces the boiler; the process moves heat out of the building instead of into it. The control architecture is nearly identical.
OAT lockout: Unlike a boiler, a chiller cannot run in very cold weather. Most chillers lock out below 40-50 degrees F outdoor air temperature.
Chilled water supply temperature reset: On mild days, delivering 48-54 degrees F water is sufficient and the chiller runs at better efficiency.
Point Map
| Point | Description | Category |
|---|---|---|
| CHW_SupTemp | Chilled Water Supply Temperature | AI |
| OAT | Outdoor Air Temperature | AI |
| CHW_DP | Loop Differential Pressure | AI |
| Pump1_Proof | Pump 1 current switch proof | BI |
| Pump2_Proof | Pump 2 current switch proof | BI |
| VFD1_Spd | Pump 1 VFD speed command 0-100% | AO |
| VFD2_Spd | Pump 2 VFD speed command 0-100% | AO |
| Chiller_En | Chiller enable relay | BO |
| Pump1_En | Pump 1 enable relay | BO |
| Pump2_En | Pump 2 enable relay | BO |
Software points: Sys_Enable (BV), Rotate_Pumps (BV), CHWST_SP (AV), DP_SP (AV).