Lennox
Restricted Return Air / High Static Pressure
Furnace is very loud at the return grille; whistling or roaring sound when running.
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Possible Causes
Filter too restrictive (high MERV) for Lennox system, Undersized return ductwork, Blocked return grilles, Closed bedroom doors without adequate undercut or transfer grilles
How to Fix / Troubleshooting
Safety: Basic airflow checks are safe; avoid altering structural components.
- 1. Replace filter: Use a Lennox-recommended filter with appropriate MERV rating.
- 2. Open returns: Ensure all return grilles are unobstructed.
- 3. Door undercuts: Keep interior doors open during heating if returns are in hallways only.
Severe static pressure issues require duct evaluation by an HVAC professional.
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Repair Difficulty
Easy
2/5
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