True Partners Consulting Engineers

CHILLER REPLACEMENT: MAKING THE CASE - A STRATEGIC APPROACH FOR COST-EFFICIENCY

Chillers, crucial in facilities for cooling, represent significant investments and electricity consumption. A recent study has shown that HVAC systems typically consume around 50-70% of a base building's energy usage (around 40% of the total building usage), with 25-40% of energy consumed by chillers producing chilled water for air-conditioning.

With a lifespan of 20-25 years, their replacement demands a careful balance between operational efficiency and cost. Data analysis underscores that running chillers may not equate to efficient functioning, especially as they age. Modern chillers, boasting efficiencies around 0.15 kWe/kWr, substantially outperform older models (0.25 kWe/kWr) in both full-load and part-load scenarios, promising notable energy savings.

However, replacing chillers isn't solely about improving efficiency. Facility Managers and Owners must consider the chiller's condition, the changing needs of the building, and maintenance complexities.

Oversizing, a common issue due to evolving building needs, can lead to inefficiency, though it's not a standalone reason for replacement, we have discussed the importance of low load chillers in a separate Forum. Maintenance and reliability, assessed through detailed chiller condition examinations and operational logs, also play pivotal roles. This includes assessing heat-exchanger tubes, system components, and leak rates, with newer chillers significantly outperforming older ones in these areas.

Developing a detailed load profile is fundamental for a good understanding of potential energy savings. This involves meticulous data collection on chiller operation, comparing current performance with potential new models. Load profiles can be generated through simulated tests or extended monitoring, each with its merits and drawbacks.

In advocating for chiller replacement, a comprehensive life-cycle cost analysis, juxtaposing the expenses of maintaining the current chiller against the investment in a new one, is crucial. This thorough evaluation, when well-presented, enhances the prospects of securing necessary funding for the replacement, positioning the project as a strategic, cost-effective solution in the long term.

UNDERSTANING CHILLER LOAD PROFILES

Creating a load profile for your chiller can really shed light on its performance, and there are two main ways to do this. You can either go for a simulated load test or opt for a more long-term approach by recording the chiller's operating parameters over several months. Whichever method you choose, you'll need to keep an eye on a few key things like electricity usage, temperatures of the chilled and condenser water (both supply and return), and the flow rates of these waters.

If your chiller is hooked up to an energy management system, that's great! You can use its trend function to gather all the data you need. If not, don't worry – portable data-loggers can step in to help collect data throughout your study.

Now, about the simulated load test – it's a bit like a quick health check-up for your chiller. You adjust the water temperature and monitor how the chiller behaves from its maximum capacity down to the lighter loads it might experience. It's a fast process, typically done in a day or two. The catch? It might not capture the full picture, especially how the chiller performs under your building's specific conditions over time.

On a recent project, after analysing the chiller log date collected over three years, our team found out the the return water temperatures were too low even during chiller's peak running hours. After further investigation, we were able to find the source of the issue which was over pumping as the chilled water pumps were pumping too much chilled water causing several issues for the chiller and the air-conditioning system such as high pump power usage and low Delta T syndrome to name a few.

If you're looking for a deep dive into your chiller's performance, consider monitoring it over several months or years, ideally covering the entire cooling season as a minimum. This approach gives you a detailed view of how your chiller handles different loads and for how long, painting a clear picture of its efficiency.

Before you start any tests, it's crucial to ensure your chiller is in top shape and all its maintenance needs are up to date. Pay special attention to the heat-exchanger tubes – if they're not clean, your efficiency readings might be off.

TPCE excels in offering cohesive energy solutions for both new constructions and upgrades of existing facilities. Our proficiency spans MEP Design, Energy Efficiency, and Data Analysis, enabling us to craft and refine energy saving measure solutions. We transform initial ideas, concepts, or spreadsheet data into comprehensive, budget-friendly packages that are ready for implementation and adhere to all compliance Australian standards.

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