What is Logic Control and Why is it Important in Energy Modeling?

Today, I want to discuss an essential feature of any robust energy modeling tool: logic controls.

First, what exactly is logic control? In simple terms, logic control defines how equipment or systems operate based on specific conditions. Think of it as an "if A, then B" statement. Here, "A" represents a condition, and "B" represents the resulting action. Some practical examples include:

• If the space temperature drops below 68°F, then activate heating.

• If daylight exceeds 300 lux, then dim electric lighting to 10%.

• If indoor air enthalpy minus outdoor air enthalpy is greater than 1, then engage the economizer.

Why is logic control crucial in energy modeling? Modern buildings have detailed sequences of operations that determine how equipment and systems perform, largely governed by advanced building automation systems (BAS). Accurately modeling these operational sequences allows energy models to closely replicate actual building behavior, resulting in more reliable predictions of energy performance and efficiency.

To illustrate this concept, let's explore how logic control is modeled in the IES-VE software. (Disclaimer: At Clearbrook Energy Solutions, we primarily use IES-VE and are most familiar with its functionalities, but other advanced modeling tools should offer similar capabilities.)

Let's begin by reviewing some basic aspects of logic control implementation in IES-VE.

Now that we've covered the basics, let's examine a practical, straightforward example. In many industrial facilities, providing adequate air changes is common. These buildings often lack active cooling systems and instead utilize a strategy known as "flushing." The goal is to introduce cooler outside air to flush and cool the building, thereby charging the thermal mass of the structure and stored goods. This helps maintain cooler temperatures during shoulder and summer months.

Here is the logic: if 60F <To < 80F & To < Ti, then turn on the MAUs and EF.

In this case, “To” is the outside air temperature and “Ti” is the internal space temperature. 

Let’s take a look at how it’s done in IES-VE.

Let’s take a look at the results. 

This simple example demonstrates the power of modeling logic controls. More complex logic sequences can be developed in a similar manner, significantly improving the accuracy and realism of energy models.

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Have questions or want to work with us? Reach out to us at allenm@clearbrook.energy.