Our customer was having difficulty controlling the primary and secondary chilled water loops within its cooling system. The chilled water flows were frequently oscillating far above and below their temperature and flow rate setpoints, causing frequent, rapid loading and unloading of not only the chilled water pumps, but also the chillers themselves. As a result, the facility was forced to ramp up its flow setpoint in order to achieve the desired cooling performance—despite the system’s extreme fluctuations. The combination of rapid equipment cycling with the elevated setpoint meant that our customer was using far more energy than necessary to operate the facility.

The control difficulties were traced back to errors in chilled water flow measurements. The existing clamp-on ultrasonic BTU meters had limitations including poor measurement accuracy, slow response time, and inadequate turndown. The inaccuracies from each of the individual flow and temperature measurements were compounded in the overall BTU calculations, leading to significant BTU measurement error. Furthermore, poor measurement response time introduced delays between flow changes and system response, which meant corrective actions were unable to keep up with real time system changes.

Another source of error was that the existing meters had been sized for peak summer usage. Due to the limited turndown capabilities of clamp-on ultrasonic flow meters, they were not able to capture the much lower winter flow rates. As a result, flow rates could not be measured for control purposes during the off-season, nor could usage be billed properly. Any routine maintenance or measurement verification required the meters be taken offline, which led to additional measurement downtime.

• Industry leading performance with flow reference accuracy of 0.15%
• Custom temperature sensor curve using Callendar-Van Dusen constants improves measurement accuracy by 75%
• Supports all main HVAC protocols: BACnet IP, BACnet MS/TP, Metasys N2, Modbus TCP, AB Ethernet IP, AB DF1, LonWorks
• Provides accurate measurements for management system to lower carbon footprint for LEED certification
• Available as single source offering through Control Associates
• Local service for design, start-up, and troubleshooting throughout the Greater NYC Metro Area