Arkansas HVACR NewsMagazine March 2026

ARHVACR NewsMagazine March2026

S tate, National, Chapter News State national Chapter News

Key Considerations for Proper Exhaust Installation

manufacturer's maximum allowable run.

1. Material Matters Use only manufacturer-approved materials. For condensing units, avoid ABS or unlisted PVC. CPVC or polypropylene piping is typically recommended. Vent pipe joints must be properly primed and glued to prevent leaks. 2. Follow the Slope Rule For condensing furnaces, exhaust pipes must slope back toward the furnace at 1/4 inch per foot to allow condensate to drain properly. Pooling inside the vent can trigger safety lockouts or corrode internal components. • Maintain required clearances from windows, doors, and fresh air intakes (typically 3 – 4 feet) • Include screens to prevent rodent or debris entry, without restricting airflow 4. Avoid Too Many Elbows Too many bends create excessive resistance, increasing the chance of vent pressure problems. Count each elbow when calculating total equivalent length and always compare this to the 3. Proper Termination Exhaust and intake terminations should: • Be at least 12 inches above expected snow levels

5. Combustion Air Matters A sealed combustion system (direct vent) pulls outside air in for combustion, reducing the risk of backdrafting and improving efficiency. In tight homes, always confirm there's adequate combustion air — whether direct or from a mechanical system. Mixing incompatible pipe materials (e.g., PVC with CPVC) • Using unsealed joints in exhaust piping • Installing exhaust too close to air intakes or wall openings • Neglecting to secure horizontal runs every 3 – 4 feet • Ignoring local and national mechanical code Common Mistakes to Avoid • International Mechanical Code (IMC) • National Fuel Gas Code (NFPA 54) • Local and state codes , which may have more stringent rules As HVAC contractors, you know that safety, efficiency, and code compliance go hand in hand. Taking the time to properly size, install, and inspect natural gas furnace exhaust systems protects your reputation and your Know the Code Always reference: •