Understanding AHRI 920-2015 and MRE (Moisture Removal Efficiency)
September 10, 2016
Understanding the basics of ANSI/AHRI 920-2015: Performance Rating of DX-Dedicated Outdoor Air System Units
ASHRAE realized that standard methods of efficiency rating (EER for example) do not accurately reflect the efficiency of a packaged DOAS system. Instead, the focus should be on moisture removal efficiency, or MRE.
2015 Standard supersedes ANSI/AHRI 920-2012 code/standard requirement for Dedicated Outdoor Air Systems (DOAS).
Based upon AHRI 920, ASHRAE 90.1 – 2016 will define and establish, for the first time, the minimum ISMRE (Integrated Seasonal Moisture Removal Efficiency) to reflect this code/standard requirement for Dedicated Outdoor Air Systems (DOAS).
The purpose of this standard is to establish for DX-Dedicated Outdoor Air System Units: definitions; classifications; test requirements; minimum data requirements for Published Ratings; operating requirements; marking and nameplate data; and conformance conditions.
The following certification program ratings are verified by test (at given Rating Conditions):
Moisture Removal Capacity, lb of moisture/h
Moisture Removal Efficiency, lb of moisture/kWh
DX-Dedicated Outdoor Air Systems (DX-DOAS) condition outdoor ventilation air independently from the building HVAC System. This approach to handling ventilation air results is superior humidity control by limiting the primary source of humidity in most buildings – ambient humidity carried in by the ventilation air – directly at its source. When the DX-DOAS removes enough moisture from the ventilation air to match the building interior load, energy savings can be obtained by running the separate, sensible cooling only, interior cooling system at a higher evaporating temperature, thus improving the energy efficiency. Further savings may be realized by providing only the amount of ventilation air necessary and/or by using energy recovery from the building Exhaust Air to pre-treat the ventilation air. Alternate energy strategies may be employed to provide ventilation air at low or high dry-bulb temperatures to assist in building cooling and heating.
Integrated Seasonal Moisture Removal Efficiency (ISMRE). This seasonal efficiency number is a combined value based on the formula listed in Section 6.5 of the four (4) dehumidification Moisture Removal Efficiency (MRE) ratings required in this standard for DX-DOAS Units expressed in lb of moisture/kWh.
What NEAP can offer : The Munters DryCool™ ERV product combines desiccant dehumidification with total energy recovery. The unit supplies 100% make-up air utilizing energy recovery from the exhaust air stream. Munters DryCool™ ERV systems offer industry leading Integrated Seasonal Moisture Removal Efficiency (ISMRE) as regulated by AHRI Standard 920 (nearly double the standard). https://www.munters.com/en/munters/products/dehumidifiers/drycool-erv/