What is an energy recovery wheel, how does it work, and why is maintaining it important?
An energy recovery wheel (ERW) is a component in a packaged HVAC unit. The ERW is a large, rotating, air permeable disc that allows for heat to be gathered from one air stream and transferred to another. The wheel is positioned where the top half has air moving through it in one direction and the bottom half has air moving through it in the opposite direction. The wheel is constantly rotating which transfers heat (energy), and sometimes humidity, from one airstream to another.
ERW’s are primarily used in commercial or industrial settings which require a high ventilation rate to meet the building codes for fresh air per hour. Anytime fresh air is drawn into a building, the same quantity of air must be forced out to maintain proper building pressure. The application where they are most commonly used is when the air being exhausted from the building is air that has already been conditioned and the air being drawn into a building (outside air) is unconditioned.
The way in which the Energy Recovery Wheel aids in this process differs depending on the season. In summer, for example, the air being exhausted will be conditioned (cooled) and dehumidified air from the “return” side of the system. This air will be mechanically pulled out of the building through the bottom half of the ERW. At the same time, there will be hot humid outdoor air being drawn in through the top portion of the wheel. Since the wheel is in continuous motion, it is constantly absorbing heat in its top half and rotating that heat down to the exhaust portion where it is displaced and vice-versa. For this process to work the wheel must be clean, and it must be rotating. Keeping an ERW clean and rotating through routine preventative maintenance is critical for the displacement of heat and proper operation. If particle buildup on the surface of the wheel is left unchecked, the amount of heat displacement and energy recovery will be substantially diminished. In cases where the wheel becomes significantly fouled, it will create an airflow restriction issue which can then lead to even bigger problems and difficulty controlling the building pressure, temperature and humidity. If the wheel is ever inoperable (not rotating), then all efficiencies gained by the design are lost.
Our team at Frigi-Temp has assisted customers across the Raleigh-Durham area with keeping their Energy Recovery Wheels operating at maximum efficiency. We are capable of not only maintaining systems with ERWs, but also fully capable of restoring inoperable and inefficient wheels.