The commercial Heating, Ventilating and Air Conditioning (HVAC) industry of North America finds itself in an increasingly difficult balancing act between providing energy-efficient systems and improving Indoor Air Quality (IAQ) for the occupants of commercial buildings. The balancing act occurs as designers work to meet the intent of 2 primary Standards produced by the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE), namely ASHRAE Standard 62.1 (Ventilation for Acceptable Indoor Air Quality) and ASHRAE Standard 90.1 (Energy Standard for Buildings Except Low-Rise Residential Buildings).
ASHRAE Standard 62.1 defines the amount of outdoor air to be brought into a conditioned space, depending on the application and occupancy rate. This outdoor air will need to be conditioned (filtered, heated, cooled, humidified, dehumidified, etc.) to meet the building design temperature and humidity levels, increasing the energy consumed by the building.
ASHRAE Standard 90.1 provides guidelines for minimizing the energy used to condition buildings, including equipment efficiency levels, conditions when equipment should be turned off, temperature set point reset conditions, etc. This Standard is also the basis for the International Energy Conservation Code (IECC), as supported by the U.S. Department of Energy (DOE).
ASHRAE also provides other Standards such as Standard 170 (Ventilation of Health Care Facilities) and Standard 189.1 (Standard for the Design of High-Performance Green Buildings) that provide more specific (and typically more stringent) requirements for meeting both IAQ and energy efficiency.
An increasingly popular methodology of meeting this balancing act is the application of air exchange energy recovery, and the most effective technology for recovering energy is an enthalpy wheel (see photo). As implied in its name, the enthalpy wheel exchanges both sensible and latent energy between the outdoor air intake and the exhaust air discharge air streams.
Enthalpy wheels can be applied to stand-alone Energy Recovery Ventilator (ERV) units, Dedicated Outdoor Air System (DOAS) units, Unitary Rooftop Units, Air Handling Units or even in field assembled built-up systems. While the consulting engineer, building owner or contractor will evaluate several factors, including the climate zone of the building as noted in Figure 1, in making the HVAC system choice, a high percentage of North America climates will benefit from applying an enthalpy wheel to the HVAC system chosen.
However, there are several factors that will influence the ultimate performance of an enthalpy wheel.
- The first factor is the medium used to capture both sensible and latent energy.
- The second factor is the percent of effective area of the wheel in relation to the total area of the casing & mounting in the HVAC equipment.
- The third factor is the amount of air leakage between the higher pressure exhaust air stream and the lower pressure outdoor air intake air stream.
- The fourth factor is the efficiency and reliability of the drive system – the motor, the belt or gearing and the bearings. Obviously if any of these components degrade easily or even fail, then the overall effectiveness of the enthalpy wheel will be compromised.
The Swiss Rotors Enthalpy Wheel is an excellent example of a highly effective enthalpy energy recovery device.
First, it uses a fast-acting 3-Angstrom molecular sieve coating for capturing and releasing both sensible and latent energy. Its anti-microbial properties also keep it operating at peak effectiveness.
Second, this coating is applied in a patent-pending continuous manufacturing process to an aluminum wheel, making a single structure.
This has an advantage over segmented wheels which require additional structure to support the segments. These segments and their supports not only add weight but also reduce the overall effective area of the wheel.
The Swiss Rotors wheel has up to 8% more effective energy recovery area over competitive segmented wheels.
Third, the Swiss Rotors enthalpy wheel has a double sealing system to minimize air leakage from exhaust to intake, increasing overall effectiveness by up to 2% over competitive designs.
Additionally, there is an optional purge device to eliminate any cross-contamination between air streams.
Fourth, the belt design used by Swiss Rotors is a segmented Fenner PowerTwist belt which has been engineered to maintain the optimal belt tension throughout the belt’s life. Eliminating the need to re-tension reduces labor cost and, more importantly, maintains the unit’s high efficiency.
The EC Motor with an Integrated VFD also adds to the overall efficient operation of the enthalpy wheel. Plus, the double wall casing, the extruded aluminum wheel hubs, and the permanently lubricated 200,000 hour (L50) bearings ensure that this high-performance enthalpy wheel will continue to reliably recover energy.
The Swiss Rotors Enthalpy Wheel is made in the USA, AHRI 1060 Certified, with quick delivery cycles, and is available in both 4” and 8” widths to easily replace existing wheel casings in retrofit applications. The SF Series has a 4” wheel and is available in 9 sizes from 32” – 76” wheel diameter. The RT Series has an 8” wheel and is available in 17 sizes with wheel diameters from 28” – 95”.
For more information, click on this link http://swissrotors.com/en/products/