During the development of the Quiet Climate “WH” 12 SEER Wall Mount Heat Pump, it was determined that designing systems with less than 400 CFM per ton has several advantages for classroom applications: energy savings, sound level reduction, and better latent removal capabilities, along with reduced drafts on the occupants. A low sound level in the classroom is highly desirable to help create a better learning environment. Some school district specifications set sound level limits on the air conditioning equipment as well as efficiency, unit feature, and minimum duct sizing requirements.

If a Wallmount is designed for use at a very low sound level, and as a free blow (non-ducted) application, lower evaporator airflow must be selected to obtain a better hvac system for classroom applications. With the reduced cfm/ton airflow, evaporator coil temperatures tend to be lower and thus latent removal capacity is improved. This is welcome in the classroom application because of the higher latent load caused by 20 to 30-student occupancy level, and the sensible/latent load from ventilation requirements applicable to classrooms.

The Bard WH261, WH311, WH381, WH431, WH491, AND WH611 series of wall mounted units were specifically designed to operate at less than 400 CFM/ton by using larger indoor coils to obtain the desired heat transfer at a lower indoor airflow. The unit is not just operating below rated design airflow. Coupled with many other new design features, these units provide a properly balanced, highly efficient, low sound level unit for free blow and ducted classroom installations unmatched in the industry, today.

Proper duct sizing, supply grille selection, and positioning of the louvers can distribute the air efficiently, quietly, and maintain room comfort. Sound levels as low, or nearly as low as, ducted systems are possible from free blow systems with the Bard Quiet Climate Heat Pump. When a free blow application is selected, installation costs have been significantly reduced because no duct system is needed. When the proper duct system is selected, the system is even quieter, and there is less “air turbulence” than conventional 400 cfm/ton systems resulting in lower noise levels.

 A popular misconception existing in the HVAC industry is that a properly designed system traditionally should supply 400 CFM of air per ton of cooling capacity, and any less is not a “perfect” system. In actuality, the user objectives, unit application, and system design should be used to determine the required airflow, not an “age-old rule of thumb”. Designing a wall-mount unit at 400 CFM per ton for classroom application would generate a higher sound level, and would supply the room with more “circulated” air than is required.

What do occupants of our portable and site built classrooms complain about the most? Noise! Teachers shut the hvac unit off because it is too noisy. Next, the occupants complain about drafty, hot and cold spots within our classrooms. Too many air changes per hour through too few supply outlets, and the teachers shut off the hvac unit. If the hvac unit is not running, there will be no ventilation (fresh air) provided to the occupants. Bard Mfg’s New Quiet Climate 12 Seer Wall Mounted heat pumps have been designed to operate at rated airflows of 312-370 CFM/ton depending on the model. These models can operate as non-ducted (on low speed) or ducted applications up to .2 ESP (on high speed.) A reduced airflow cooling system is obviously the best match for the classroom application, and for any application that requires a very low sound level, and good latent removal capabilities with significant energy savings.