Can you spot the flaw here?
Answer: A Fan With A Broken Back!
Why: What does it mean to break a fan’s back? Well, when you don’t abide by the basic fan laws or installation guides some poor fans will be set up for a lifetime of failure.
For starters, this supply fan doesn’t have the correct downstream duct design or installation. Fan installation guides will dictate the minimum length of straight run of duct needed downstream of the fan’s outlet. This is normally 3 to 5 duct diameters and it helps develop the air’s dynamic characteristics. Additionally, the direction in which the air is forced, downstream of the fan is in the opposite rotation than the fan which increases pressure drop and upsets the airflow. To help this fan’s “back”, the fan’s orientation could be flipped or adjusted. Also, if roof space permits, it would be recommended to provide a straight run of duct downstream of the fan before any fittings such as elbows.
Thank you to Kari Rosteck, Field Engineer for sharing!