Challenges for chilled water systems and total cost of ownership
In this module, you will learn about some of the challenges facing air conditioning systems with particular focus on low Delta T syndrome, and how FLOWLIMIT can improve Delta T to reduce the total cost of ownership.
Welcome to this ECADEMY module about the challenges facing air conditioning systems and the implications for total cost of ownership.
In this module, we will discuss:
- Some of these challenges, with particular focus on low Delta T syndrome;
- The most critical consequences if not resolved; and,
- How intelligent pumps enable the energy savings that lower costs.
Let’s start with the main challenges facing air conditioning systems.
One of many reasons why so many systems are out of balance is because the commissioning of air conditioning systems is generally poorly done.
Another reason is if pumps are not being monitored or integrated into Building Management Systems (BMS), with the potentially critical consequences of out-dated and worn-out pumps resulting in low pump efficiency in HVAC systems. This might lead to, among other issues, the building’s actual energy consumption exceeding the designed energy consumption.
The result is lower end-user comfort and increased costs across the board, for example, from operations, service and an inability to optimise the system. The above challenges can also contribute to low Delta T syndrome, and this is the most critical challenge facing air conditioning systems.
Low Delta T syndrome occurs when the chilled water temperature range for which the system is designed is not maintained. The issues that arise from not maintaining the system-designed Delta T range can result in excessive chilled water overflow as well as components operating outside their design frame and therefore outside the best efficiency point.
This leads to poor system performance, excessive energy usage and bad comfort. If Delta T range in a chilled water system decreases too far, the flow rate must be increased significantly to maintain sufficient cooling in the building.
Let’s look at the main root causes of low Delta T:
- The HVAC system is out of balance and there is overflow or starvation between the zones meaning the system is not cooling properly;
- Undersized or dirty cooling coils that are not able to achieve the required return temperatures;
- Oversized or faulty control valves; and
- Oversized, uncontrolled pumps or pumps operated in the ‘wrong’ control mode, not allowing the pump to adapt performance to load variations.
This could lead to higher pump and chiller energy usage if failing to achieve the proper return temperature, resulting in a compromised Delta T, or if costs increase due to:
- Increased cost for chilled water distribution; and,
- Decreased chiller efficiency.
There are various ways to overcome these challenges. One example is the FLOWLIMIT functionality, which is an electronic flow commissioning functionality built into the pump.
FLOWLIMIT limits the pumps performance when the design flow is reached and makes sure that overflow does not occur. In this way FLOWLIMIT contributes to improving Delta T. FLOWLIMIT also enables more efficient balancing of the air conditioning system and it eliminates the need for pump throttling valves, as the pumps adjust flow levels accurately to only what is demanded in the system.
Using intelligent Grundfos pumps provides many advantages, because they:
- Reduce chilled water distribution cost;
- Reduce over pumping in the system and increase the system’s Delta T;
- Reduce system energy consumption and improve system efficiency;
- Increase system controllability; and,
- Increase end user comfort and satisfaction.
That concludes this look at some of the challenges facing air conditioning systems with particular focus on low Delta T syndrome and the implications for total cost of ownership.