Furnace is very loud at the return grille, with whistling or roaring air noise.

Safety First: Turn off power before changing filters or opening ductwork.

• Use proper filter: Replace high-MERV restrictive filters with a filter type recommended by Thermo Pride or your installer.
• Open doors: Keep interior doors open to allow air to return to the furnace.
• Clear return grilles: Move furniture and objects away from return grilles.
• Professional duct evaluation: If noise persists, a contractor may need to enlarge return ducts or add additional returns.