Delta T (ΔT)

Delta T, or the difference in temperature between a heating or cooling medium as it enters and leaves an HVAC system, is one of the most important concepts to understand when working with HVAC systems.

This concept is critical for understanding how to properly size an HVAC unit–the amount of Delta T that can be absorbed by the system will determine its efficiency and lifespan. While there are many different types of HVAC systems, they typically fall into one of two categories: air-to-air heat pumps (which rely on air as their heat source) or water-to-air heat pumps (which use water as their heat source).

The amount of Delta T that a particular HVAC system can absorb will depend on its design and capacity. For example, a smaller air-to-air heat pump might only be able to absorb a Delta T of 20 degrees, while a larger water-to-air heat pump could absorb a Delta T of 30 degrees or more.

When sizing an HVAC system, it’s important to consider not only the desired Delta T but also the temperature of the heating or cooling medium as it enters and leaves the system. If the temperature of the medium is too high or too low, it can cause damage to the system.

For example, if the temperature of the cooling medium entering an air-to-air heat pump is too high, it can cause the compressor to overheat and fail. Conversely, if the temperature of the heating medium entering a water-to-air heat pump is too low, it can cause the system to freeze and stop working.

In order to avoid these problems, it’s important to select an HVAC system that is properly sized for the application and has a suitable Delta T range. With a little bit of planning and careful selection, you can ensure that your HVAC system will provide years of reliable operation.

While Delta T is an important concept to understand when working with HVAC systems, it can sometimes be difficult to visualize or grasp. One approach to help you better understand this concept is to think about the temperature of a heating or cooling medium as it enters and leaves the system on a line graph.

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