Armstrong Air Return Air Restriction or Undersized Return

The furnace is very loud at the return grille, with a whistling or roaring sound when running.

Possible Causes

Filter too restrictive, return grille too small, blocked return duct, closed doors without undercut in rooms.

Steps to check:

Filter type: Replace high-MERV or thick media filters with Armstrong Air-recommended filters if ductwork is not designed for high resistance.
Open returns: Ensure all return grilles are unobstructed and clean.
Door undercuts: Interior doors should have enough clearance at the bottom to allow air to return when closed.
Consult HVAC pro: If noise persists, a larger return or additional returns may be needed.

Easy 2/5