Does Chaining Two UPS Increase Capacity?

When considering power protection for critical systems, many organizations wonder whether chaining two Uninterruptible Power Supplies (UPS) can increase overall system capacity and reliability. Understanding the complexities involved is crucial for making informed decisions that optimize efficiency and cost-effectiveness.

Exploring the Basics of UPS

Uninterruptible Power Supplies (UPS) are designed to provide continuous power to connected devices by seamlessly switching between different sources, often including grid power and backup batteries. There are several models available, with different features including support for additional power packs for extended runtime.

The Lure of Added Capacity

One might think that chaining two UPS units would double the available power capacity, thereby enhancing system reliability and longevity. However, this is not without significant drawbacks and potential complications.

The Pitfalls of Chaining Two UPS

When chaining two UPS units, it is important to understand the associated losses and inefficiencies. Specifically:

Increased Power Consumption: Connecting the first UPS to power the second UPS will result in various additional losses, ultimately increasing your overall power bill. Dependency on Size of First UPS: The first UPS must be larger or more powerful than the second to manage its full load plus the second's load, the charging power, and the internal losses of the second UPS. Complexity in Runtime Calculation: The runtime calculation becomes more complicated when both UPS units are in use. It’s difficult to determine the true battery runtime and recovery time accurately. Inaccurate Power Management: The batteries in the second UPS might indicate that there is more time left for shutdown, leading to further unnecessary power consumption until the first UPS triggers a shutdown.

These complications can lead to inefficiencies and higher operational costs. Instead of relying on chaining UPS units, it is often more effective to focus on selecting the right-sized UPS to meet the needs of the connected load.

Optimal UPS Selection

A more economically viable solution often involves purchasing a single UPS that can deliver the required power for a longer period. For instance, rather than buying two UPS units that each provide 1 kW for 30 minutes, a single UPS delivering 1 kW for 60 minutes would serve the same purpose but at a lower cost. This approach simplifies system management and reduces the likelihood of operational issues.

Avoiding the Risks with Parallel Connection

Even if you consider connecting the two UPS units in parallel, it is crucial to note that unless they are specifically designed for this configuration, attempting such an arrangement is risky. Parallel connection requires specialized equipment and expertise to ensure stability and avoid system failures.

In conclusion, while the idea of chaining two UPS units to increase capacity might seem appealing at first, the complications and potential losses outweigh the benefits. Opting for a single, well-sized UPS or carefully selecting UPS units for parallel connection are generally more practical and cost-effective choices for power management.