Temperature Chamber Considerations: System Components & Power

Purchasing a new environmental test chamber requires the careful consideration of a number of key factors, including size, testing requirements, and materials. Other important considerations that are often misunderstood or overlooked are the optimal components of the cooling system and the level of power required for your testing needs. This is most relevant for temperature chambers and refers to the mechanisms and change rates at which a device under testing (DUT) can be fully brought to the desired temperature.

Effectively weighing these considerations will require a comprehensive understanding of the type of testing you’re looking to conduct, your priorities in that testing, and the devices that will undergo testing.

Compressor Systems and Condensers

A test chamber’s ability to reach certain low temperatures will depend partially on the type of refrigeration compressor system it is built with. The two most common options are single-stage and cascade. Single-stage refrigeration compressor systems are typically sufficient to reach temperatures as low as -40ºC. Testing requirements below that, however, will necessitate the use of a cascade refrigeration compressor system, in which two independent circuits with their own refrigerate take turns bringing the temperature progressively lower. By working the compressors in tandem and allowing each time to recover, this system reduces strain on the system. Test chambers making use of cascade refrigeration compressor systems, therefore, can reach temperatures as low as -75 to -80ºC (-103 to -112°F).

Be sure to inquire about additional characteristics of a chamber’s compressor as well. Hermetically and semi-hermetically sealed compressors, for instance, require almost no maintenance. Moreover, scroll compressors, which lack valves, are highly efficient and should be considered for smaller test chamber workspaces. Should you instead require Discus compressor technology to accommodate active live loads and large workspaces, you can rest assured that advancements in such technology have also improved their efficiency. 

The condenser system in your test chamber will also influence its performance. Some chambers can operate on either air-cooled or water-cooled condensers and achieve the same performance. Others, however, will see a difference in the two units. Water-cooled units, often, bring down the temperature at a faster rate than their air-cooled counterparts, but require a dedicated conditioned water line. If you don’t have access to a water line, larger, external air-cooled condensers are effective options.

The chart below will help you compare these and other important condenser characteristics.

Test Chamber Power

The power with which a test chamber operates, measured in horsepower, is a leading indicator of how quickly DUTs will be able to reach the desired temperature. While it might seem natural to seek out the most powerful chamber within your budget, it’s not actually that simple. 

Proper testing calls for the DUT to be brought to the desired temperature all the way through. Anyone who has ever cooked a Thanksgiving turkey knows that an item in a heated environment does not heat up all at once—the heat starting on the most outer layer and progressively moves inward. The same is true for any device you need to test. 

As this heating process occurs, the DUT absorbs some of the heat from the environment around it. To compensate for this loss of heat in the workspace and maintain the heating process, the test chamber must continuously pull air into its intake, reheat it, and propel it back into the workspace through its fan—this requires a certain amount of power.

How much power is required to maintain this process is not consistent for every device one intends to test.

It depends on the materials that make up the DUT: Plastic absorbs heat at a different rate than steel, for example. That’s why it’s important to understand the makeup of the DUT and the weight of each constituent, and then ask your chamber manufacturer about reaching your desired ramp rates. 

You can find a chart listing absorptivities of common materials here, though we encourage you to discuss this with your internal team and test chamber sales team to ensure that you have the most accurate information about your products.

Therefore, the appropriate power your test chamber should have will depend on the devices you expect to test the most.

It might be tempting to pay a higher price for a chamber boasting greater power, but if the devices you anticipate testing are known to have low absorptivity, then that greater power will not be necessary. In this case, a chamber with lower power would be sufficient and save you money in the process.

Conversely, you may want to opt for a chamber with lower power that is less expensive. While this might sound like a cost-effective choice on the surface, this too could end up costing you indirectly if your devices have high absorptivities. This is because such devices will absorb heat faster than the chamber will be able to reheat and circulate the air, meaning it could take hours or even days longer to adequately heat your devices and complete your testing.

And when time is money, extended testing timelines could end up costing you more in the long term than the upfront cost for a more powerful chamber. 

With the right answer being so heavily dependent on your specific testing needs, it’s important to express to your chamber manufacturer what you intend to test. Rather than encouraging you to purchase a more expensive chamber with potentially inappropriate capabilities, the best manufacturers will work to find a solution that fits your unique set of needs.

Associated Environmental Systems, for instance, has made its four standard change rate categories—Thrust, Impulse, Warp, and Hyperdrive—available in all of our test chamber floor models. And if your testing requirements do not match our available models, we will work with you to build a custom chamber. 

No matter your needs, AES is here to ensure that you have the right combination of size, performance, and power to carry out the testing you need. Contact us today to let us know how we can help you optimize your testing operations.