In many commercial buildings, HVAC systems are responsible for a large portion of energy consumption. An average of 10% of a building’s energy use can go toward conditioning recirculated air. For larger properties, this number can climb up to 20%, according to data from the Commercial Building Energy Consumption Survey (CBECS). One effective way to reduce this energy consumption is by installing an economizer, a device that takes advantage of outdoor air to cool your building, reducing the need for mechanical cooling.
What is an HVAC Economizer?
An economizer is a component of your HVAC system, typically mounted on the roof of commercial buildings. The economizer monitors both temperature and humidity levels of outside air. When conditions are favorable, it uses the outdoor air to cool the building. Equipped with sensors and logic controllers, the economizer continuously evaluates the quality of the air. It then adjusts the intake of fresh air using dampers, controlling how much air is brought in, recirculated, or exhausted from the building.
How Free Cooling Works
An economizer reduces energy consumption by relying on outside air for cooling instead of using the A/C system. This approach, called “free cooling,” offers several benefits:
- Energy Savings: Since the A/C unit runs less, you can lower your cooling costs and reduce your dependence on electricity.
- Longer Equipment Life: Reduced use of the A/C unit means less wear and tear on your system. This results in fewer maintenance needs and a longer lifespan for your equipment.
- Improved Air Quality: Economizers bring in fresh air from the outside, improving ventilation and air quality. This is particularly helpful in older buildings that were not designed with modern air quality standards in mind. Fresh air is crucial for maintaining a healthy indoor environment, and studies have shown that better air quality leads to increased productivity.
The Benefits of Adding an Economizer
Economizers provide several advantages that are valuable for building managers focused on saving money and reducing energy consumption:
- Cost Savings: Economizers can lead to significant savings. With proper maintenance, you can expect to save at least 10% on electricity costs annually.
- Reduced Wear on A/C Units: The use of an economizer means your compressor will operate less frequently. This reduces the need for costly repairs and prolongs the time between major replacements.
- CO2 Monitoring: Some economizers are equipped with sensors to measure carbon dioxide levels in the air. When the number of people in the building increases, CO2 levels rise. The economizer automatically adjusts to bring in more fresh air, improving ventilation and comfort.
- Integration with Building Analytics Systems: If your building uses a Building Analytics System (BAS), you can integrate the economizer for 24/7 monitoring. The system can track changes in air quality and offer suggestions for improving ventilation and energy efficiency.
Things to Consider Before Adding an Economizer
Before installing an economizer, there are a few factors to consider to ensure it will work efficiently for your building:
- Climate: Economizers work best in climates where the outside air is cool and dry enough to be used for cooling. They are less effective in hot and humid environments. If you’re unsure whether your climate is suitable, check the International Energy Conservation Code (IECC), which mandates economizers for new construction or major renovations in systems exceeding 33,000 BTU/h.
- Building Type: Economizers are well-suited for buildings of all sizes. They are especially beneficial for mission-critical spaces like data centers or buildings with year-round cooling needs. However, buildings with humidified spaces, such as hospitals or museums, may not be ideal candidates.
- Retrofitting: Installing an economizer does not require major structural changes. The unit is compact and can be added to your existing HVAC system. It’s typically placed on the roof or external wall, connecting to the air handling unit’s intake plenum with motorized dampers.
- Durability: Since economizers are exposed to weather, selecting durable materials is important. The dampers should be low-leakage to prevent inefficiency when the system is not in use.
Challenges and How to Overcome Them
While economizers offer significant benefits, they can present challenges if not properly maintained. Here are a few potential issues and how to address them:
- Improper Temperature Sensor Type: Economizers often use enthalpy-based controls, which account for both temperature and humidity. These sensors can lose calibration over time, leading to wasted energy. Temperature-based controls may be more cost-effective in some situations when maintenance and operational costs are factored in.
- Oversized Return Air Dampers: To ensure proper airflow, return air dampers need sufficient air velocity. If the air velocity is too low, it can impact performance. Check the air velocity across the return air damper and, if necessary, adjust the system to improve efficiency.
- Inadequate Pressure Relief: Economizers require proper pressure relief to prevent issues like doors standing open or reduced airflow. If there is a significant pressure difference between the inside and outside of the building, inspect the relief air system for adequate airflow and control.
- Poor Sensor Placement: Proper placement of temperature and enthalpy sensors is important for accurate operation. Ensure that the outside air sensor is not exposed to direct sunlight or positioned too close to air outlets. Mixed air sensors should be placed in an area with good air circulation to ensure proper mixing.
A regular maintenance program is the best way to manage these challenges. Routine checks of sensors, air ducts, and controls are important for ensuring that the economizer continues to perform at its best. Your BAS will provide helpful alerts, but a weekly inspection is a good idea to catch any potential issues early.
How Unitemp Supports Economizer Solutions
For over 50 years, Unitemp has been a trusted provider of HVAC design, installation, renovation, and service in New Jersey and New York. If you’re considering adding an economizer to your building, our engineers can evaluate your facility’s existing equipment and recommend the best solution.
We offer comprehensive services, including engineering plans, integration with your current system, installation, and commissioning. After installation, we provide customized maintenance programs to ensure the economizer continues to provide energy savings. Additionally, we can introduce the latest HVAC technology, such as 24/7 monitoring, to help you optimize your system’s performance and extend the life of your equipment.
Call us today at 877.735.0664 for a free consultation and facility analysis. Let Unitemp help you improve your HVAC system’s efficiency and save on operating costs with an economizer solution.