Common School HVAC Retrofit Challenge:
Outdated Unit Ventilators Causing Humidity Issues & Poor IAQ
The Nodaway Valley School District faced a significant challenge with their aging R-22 direct expansion (DX) unit ventilators. These units, responsible for maintaining classroom temperature and air quality, were oversized due to recent renovations, leading to short cycling, excess humidity, and compromised indoor air quality.
Another critical issue was the excessive noise produced by the unit ventilators. The high airflow exceeded ASHRAE’s noise standard of NC 30 (equivalent to 40 dBA), disrupting the learning environment and leading to teacher complaints. To comply with ASHRAE guidelines, the school district installed fan speed controls to reduce airflow noise, successfully eliminating the whistling sound from the grates.
However, lowering the fan speed created an unintended consequence—a drop in discharge temperature at the evaporator coil. This led to the inactive hot water heating coils freezing and bursting, causing significant mechanical damage and costly repairs.
Compounding the issue, replacing unit ventilators proved to be a major obstacle due to the limited footprint available for these units. Finding a suitable replacement without major structural changes was costly and impractical, making it critical to find an alternative solution that worked within the existing infrastructure.
Best School HVAC Retrofit Solution:
The APR Control for True Load Matching
To avoid costly equipment replacement and maximize system efficiency, the school district opted to retrofit their existing unit ventilators with Rawal Devices’ APR Control. This solution enabled variable capacity modulation, allowing for lower fan speeds & the HVAC system to match cooling output to actual classroom conditions, eliminating short cycling and improving humidity control.
By implementing APR Control, the district:
✔ Optimized Dehumidification – Prevents overcooling while ensuring proper moisture removal, significantly improving indoor air quality.
✔ Extended Equipment Life – Reduced compressor short cycling, minimizing wear and tear on HVAC components.
✔ Improve dehumidification—preventing coil freezing and ensuring proper moisture removal.
✔ Retrofitted Without Major Modifications – Allowed the school to upgrade performance without replacing unit ventilators, avoiding expensive reconstruction & downtime, and complying with ASHRAE noise standards.
Results: A Cost-Effective Solution for Sustainable HVAC Performance
With APR Control, the Nodaway Valley School District successfully:
✅ Eliminated Short Cycling – Leading to more stable temperature control and better air quality in classrooms.
✅ Reduced Humidity & Improved Comfort – Ensuring a healthier learning environment for students and staff.
✅ Saved on Replacement Costs – By retrofitting instead of replacing unit ventilators, the district avoided a costly system overhaul.
✅ Reduced Equipment Failures & Costly Repairs— Improving system reliability by ensuring quiet, efficient operation to prevent hot water coil bursts while maintaining ASHRAE noise compliance.
The APR Control retrofit provided a long-term, budget-friendly solution that enhanced comfort and reliability without the disruption and financial burden of full equipment replacement.
Upgrade Your School’s HVAC Without Costly Replacements
School facilities managers face tight budgets and aging equipment, but Rawal Devices’ APR Control offers an efficient, cost-effective retrofit solution to improve humidity control, air quality, and system performance.
Contact us today to learn how the APR Control can help your school optimize HVAC performance without replacing unit ventilators!
