When people think of a load bank, they most often think of testing a power source such as a backup generator. Commonly, a load bank is used to apply load to a generator so that load bank power consumption and engine-generator performance data can be recorded and evaluated against test criteria. In these tests, the spatial arrangements of equipment are simple … The generator or generators are typically located in one place and connected to a load bank or load banks that are placed in another. The load bank(s) then operate at levels specified by the test protocol and the response of the generator equipment is recorded to evaluate its performance.

At data centers, load banks are used during commissioning to evaluate whether power distribution systems can deliver adequate power throughout a facility. Load banks are also used to generate heat to test the performance of cooling systems across IT equipment spaces. Whether for power or cooling, these distributed systems require multiple load banks to evaluate conditions at multiple locations.

The common approach to this work is to place load banks throughout the area or areas under test, then operate the power and/or cooling system to evaluate adequacy and performance. This requires testers to connect and control multiple load banks as a network.

Conditions of Test

In a hypothetical and oversimplified example, producing heat to test the cooling system for a large data center space might require three megawatts of load bank capacity. Assuming that cooling conditions would be uniform across the space, one might consider supplying two 1.5-megawatt load banks to generate the necessary heat. However, this would result in two very hot areas surrounded by increasingly cool locations with distance from each heat source. Generating the same total load using a greater number of load banks with lesser output would distribute the heat more evenly – for example, 20 load banks distributed across the same space, each generating heat from ~150 kilowatts of load, would produce more uniform heating for this test.

In practice, however, environmental conditions across data center spaces usually are not uniform, and testing organizations do not necessarily offer a selection of load banks with the exact maximum output required for each test location. Some of the data center equipment and systems will operate at a higher power density than others. Some IT equipment may see greater variations in load over time than other types. Cooling schemes such as hot aisle/cold aisle arrangements may intentionally produce varying temperatures across spaces. Likewise, a power distribution system could need to supply different amounts of power to meet the operating demands of the equipment and systems at each place. As a result, high-capacity load banks may need to be operated at partial capacity to provide the load or heat required at a particular location. For these reasons and more, testers need the ability to adjust the amount of load that load banks collectively and individually apply.

Connecting Multiple Load Banks

On Avtron load banks, the simplest form of load bank control is provided by switches on each unit. These are useful for simple test applications and to back up other types of control devices. Simple and precise, they nonetheless require a person to move to every load bank to adjust controls every time a change in load is needed. Beyond the inconvenience, delay, and loss of productivity this entails, it prevents the load banks from changing state simultaneously when the output of a cooling or power system is increased or decreased, reducing test precision.

Connecting the controls for each load bank to a common control terminal streamlines the operation of multiple load banks. The Avtron SIGMA LT Handheld is such a device, shown in Figure 1. By connecting load banks through daisy-chained CAN Bus control cables, testers can remotely control up to 25 load banks from a single location, avoiding the productivity loss and imprecision associated with traveling to each unit to make changes. Set up is easy – when connected, units identify themselves to the handheld and automatically assist in establishing communications.