We’ve all heard the term, “heat recovery”, “energy recovery”, “total enthalpy”, “heat wheels”, “heat pipes”, etc., they all save energy and they all have their place in specific HVAC applications best suited to each job to meet ventilation code and the designers/owners requirement to treat outdoor air. Bard, manufacturers of packaged wall-mount and indoor mount HVAC units uses the “Total Energy Wheel” in commercial applications where the ventilation code requires the introduction of outdoor air.
This energy recovery wheel (ERV) is exclusively well suited in our southeastern climate where high outdoor temperatures are accompanied by high humidity levels so removing moisture from this outdoor air becomes critically important. Heat Recovery Ventilator (HRV) or Energy Recovery Ventilator (ERV)… both are closely related: – HRV: Used mostly in northern regions, during winter seasons to reclaim energy from the exhausted indoor air to temper incoming cold, fresh air. – ERV: Recommended in southern, hot, humid climates; it is designed to remove heat, but most importantly to remove humidity from incoming fresh air, transferring moisture from humid outside air to the exhausted indoor air. The Bard ERV: The energy recovery wheel is coated with silica gel desiccant and permanently bonded. The rotary wheels are in an insulated cassette with seals, drive motors and the intake and exhaust air can be individually adjusted to maintain a positive pressure; another huge benefit is to minimize infiltration and permeation of humid outdoor air.
Let’s look at the illustration again to demonstrate the ERV in action: Entering air at design conditions: 95F DB / 78F WB = 118 Grains of moisture per pound of dry air Leaving ERV air: 87F DB / 74F WB = 106 Grains of moisture per pound of dry air (water removed) ERV Entering outside air at design conditions: 71.8F Dew point temperature Leaving ERV air: 68.8F Dew point temperature (water removed) In the real world: A classroom of 25 students or an office building with employees using 10 CFM per person plus 0.12 CFM/SF (per FBC/ASRHAE 62.1) for approximate 375 CFM ventilation, code outdoor air. Approximate Amount of Energy Recovered from Outdoor air: 14,000 BTUH of Total heat recovered 5,345 BTUH of Sensible heat recovered 8,655 BTUH of Latent heat recovered Worth noting that 14,000 BTUH is more than ONE ton total load but even more important the latent portion is almost 60% of this recovered energy, a critical component in the design and sizing of our equipment that an engineer can take credit for and reduce the size of the equipment by ONE ton. Conclusion: The Bard Energy Recovery Wheel (ERV) is the best choice for designers to use to recover energy from outdoor air, transfer humidity and meet the Florida Building Code, ASHRAE and Local Air Quality Standards in our Southeast climate. Bard’s ERV is third party, AHRI Certified to meet published performance data. The AHRI Certification for ERV’s is also a requirement from the many power companies offering energy saving rebates. For more information about Bard’s full line of packaged HVAC units featuring energy saving ERV’s please contact… Frank B. Suranyi, MBA, Member ASHRAE-Engineered Products Manager – AccuAir, Inc.
Call Frank at 407 259-0089 or you can email him at frank@accuaironline.com
