“This fan coil unit was supposed to deliver 800 cfm yet total airflow at the outlets was only 30 cfm…”
This is a photo showing a portion of a heating coil inside an HVAC unit. I wish I could have got better pictures but access to the unit was very poor.
What you are looking at is white mould that was caked onto this coil. I was measuring airflow at the outlets; this fan coil unit was supposed to deliver 800 cfm yet total airflow at the outlets was only 30 cfm – less than 5% of the required airflow! I removed a couple of side panels on the unit and saw, to my horror, that the heating coil was completely caked in this mould. It will be cleaned by the building maintenance contractor.
I’m not exactly sure what led to this problem but I suspect it started with poor access to the filter. Whomever was responsible for maintaining this particular fan coil might have been unaware of it’s existence due to poor access, or simply avoided contact with this fan coil for the same reason (poor access). As a result of the filter not being changed it became so dirty that couldn’t pass air. Eventually it was sucked into the blower plenum and then not changed or inspected for several years. The coil itself was acting as a filter, accumulating airborne particles.
