Adding a chiller in a VPF system

System Configurations

flow nears the maximum limit for the operating chiller(s), another machine must be brought online. Similarly, as the system load and flow decrease, chillers must be shut down to reduce the need for bypass water flow.

The simplest way to control a VPF system is to monitor the leaving- evaporator water temperature and allow the operating chiller(s) to load almost fully before bringing the next chiller online. As long as the system can maintain the target temperature, there is no need to activate another chiller.

When the operating chiller(s) no longer provide enough cooling, the plant controller should start the next chiller. For example, when the temperature exceeds the design setpoint by a certain amount (for example, 1.5°F [0.8°C]) for a set time (for example, 15 minutes) an additional chiller starts.

One caveat: The next chiller should start before the chilled water flow reaches the maximum limit of the operating chiller(s), even if the operating chillers are not yet fully loaded. (This would rarely happen; most pipe velocity limits are below that of the chillers.)

As chillers are brought online, flow rates may fluctuate substantially, and this occurs quite often in a system with two chillers. All systems, with any number of chillers, will find the most difficult transition when adding or subtracting the second chiller. An example will help explain the challenges.

Table 16. Flow-rate-fluctuation examples

	Design	Minimum	Maximum
	flow rate	flow rate	flow rate
	gpm [L/s]	gpm [L/s]	gpm [L/s]

Chiller 1	960 [60.6]	576 [36.3]	2,110 [133.1]

Chiller 2	1,440 [90.8]	675 [42.6]	2,474 [156.1]

At a point in time, Chiller 1 is active and has 1,100 gpm [69.4 L/s] flowing through its evaporator. It can no longer satisfy the required system supply temperature. What happens if Chiller 2’s valve is opened with no other action taken? If we assume that pressure drops are equal, 550 gpm [34.7 L/s] will flow through each chiller. This means Chiller 1’s flow rate drops by 50 percent as fast as Chiller 2’s isolation valve opens (probably beyond what its controls can respond to) and we are below each chiller’s minimum flow rate. Be aware that this could become an issue since chiller controls may protect the chiller by shutting it off. The result is that some combination of pump speed, bypass valve control, and slow-acting valves at the chillers must do two things:

•Keep change in flow rate within the equipment limitations

•Keep each chiller’s flow rate above its minimum

Chiller System Design and Control

SYS-APM001-EN

SYS-APM001-EN specifications

The Trane SYS-APM001-EN is an advanced control system designed for HVAC (Heating, Ventilation, and Air Conditioning) applications, specifically tailored to enhance energy efficiency and system performance. This comprehensive solution integrates cutting-edge technologies to optimize climate control in commercial and industrial environments.

One of the main features of the SYS-APM001-EN is its intuitive user interface. The system is equipped with a large, easy-to-read display that provides real-time data on system performance, energy usage, and environmental conditions. This user-friendly interface makes it simple for operators to monitor and adjust settings, ensuring optimal comfort levels and efficient energy consumption.

Another key characteristic of the SYS-APM001-EN is its advanced data analytics capabilities. The system collects and analyzes data from various sensors throughout the building, providing insights into occupancy patterns, equipment performance, and energy consumption trends. This data-driven approach allows facility managers to make informed decisions about system adjustments, predictive maintenance, and energy savings.

The SYS-APM001-EN also boasts robust integration capabilities. It can seamlessly connect with a variety of building management systems (BMS) and other third-party devices. This interoperability enables a cohesive operational ecosystem where HVAC systems can communicate and cooperate with lighting, security, and fire safety systems, enhancing overall building efficiency.

Energy efficiency is a hallmark of the SYS-APM001-EN, as it implements sophisticated algorithms to optimize system operation. These algorithms adjust equipment performance in real-time based on current conditions, thereby reducing energy waste and lowering operational costs. The system is designed to support multiple energy-saving strategies, including demand-controlled ventilation and optimal start/stop scheduling.

Additionally, the SYS-APM001-EN is built with scalability in mind, accommodating facilities of various sizes and configurations. Whether it’s a small office building or a large industrial complex, the system can be tailored to meet specific needs, ensuring that HVAC performance aligns with operational goals.

In conclusion, the Trane SYS-APM001-EN is an innovative HVAC control solution that emphasizes user experience, data-driven decision-making, and energy efficiency. With its advanced features and technologies, it is an essential tool for optimizing building performance and enhancing occupant comfort while reducing environmental impact.

Trane SYS-APM001-EN manual Adding a chiller in a VPF system, Flow-rate-fluctuation examples

Models: SYS-APM001-EN

System Configurations