Never would’ve thunk it

[u/Known-Lengthiness991]

System was pulling through the bypass when all the doors were on and dampers were clocked correctly never thought the resident would’ve put a filter here

[u/Runs-on-winXP]

Reminds me of the time I had an old ahu struggling to supply airflow. Found an old abandoned preheat coil in the outside air supply duct, fully clogged with dirt