Engineers designing commercial HVAC systems for use in schools, hospitals, factories or office buildings face a host of conflicts and tradeoffs when trying to comply with both ASHRAE Standard 90.1 for Energy Efficiency and ASHRAE Standard 62.1 for Indoor Air Quality (IAQ). To help engineers achieve a successful balance between the two, a new technical brief, “No More Tradeoffs: Designing DX AC Systems to Meet ASHRAE’s IAQ and Energy Savings Standards" is now available for downloading, from Rawal Devices, Inc.

Over the past decades, ASHRAE 90.1 promoted energy efficiency as a predominant design factor in air conditioning equipment. Standards for building design, insulation, glass, and ventilation were affected by the amount of thermal energy brought in from the outside air. More recently, ASHRAE 62.1 emphasized IAQ requirements and focused on proper ventilation and humidity control for operations and health issues. Studies meanwhile have confirmed the problems caused by tight, energy-efficient buildings that do not have correct ventilation. As a result, engineers face a balancing act between energy savings and IAQ in AC system design.

The new technical brief, “No More Tradeoffs…,” presents the solution as the use of the direct expansion (DX) air conditioning “discharge air temperature” reset concept (based upon outdoor air conditions), plus continuous capacity modulation for the refrigeration circuit. Discussing the limitations of DX AC design, the brief details the “temperature reset with capacity modulation” solution with sample data and calculations. Several effective approaches are explored, including the use of VFD and digital compressors, and the Rawal APR-E electronic control.

Rawal Devices is the manufacturer of highly efficient and cost-effective solutions that solve temperature and humidity control problems in industrial, institutional, and commercial building applications.