The air handling unit (AHU), or rooftop unit (RTU) if it's located on the roof, is the heart of a commercial HVAC system. Most commercial cleaning jobs include cleaning both the AHUs/RTUs and their associated ductwork. When estimating these jobs, the commercial project estimator will consider the unit's location and how difficult it is to access (e.g., a hanging AHU), its size, the labor involved in removing the access panels, and of course, how dirty the unit is.
Preparation for AHU/RTU cleaning
Before cleaning can take place, lockout/tagout procedures must be implemented in order to ensure a safe work environment. If there are smoke sensors in the ducts, the system should be put into test mode for the duration of the work. All access panels to the unit are opened, and air filters removed. In order to protect electrical components and the supply and return drops, 2- or 4-mil polyethylene sheeting is placed.
The cleaning process
Cleaning of the unit begins with a HEPA-filtered dry vacuum. All interior-insulated surfaces are vacuumed in order to remove larger debris. The commercial technician will then apply degreaser to the fan and other metal components inside the unit to remove grease that's been previously applied and has built up over time. A pressure-washer is then taken to the unit, and, if necessary, a scrubbing pad for hard-to-remove debris.
To clean the unit's heating and cooling coils, a coil cleaner is applied with a sprayer and allowed to sit a few minutes until foaming. Once the foam has worked its magic, the technician uses a pressure-washer to rinse it off at a downward angle, toward the drain pan. The drain pan itself is then cleaned with a pressure washer and wet-vacuum.
One of the final steps in the process is to ensure that the drain line is properly draining, as overflow from the drain line would fill the drain pan and enter the supply duct line, potentially contributing to mold growth on the insulation.
When the cleaning is complete, all excess water is wet-vacuumed and dry rags are used to wipe metal surfaces if needed. The unit is then reassembled and all access panels replaced.
The benefits of air handling unit cleaning
Your building's occupants and your HVAC system will thank you. Cleaning of the air handling unit and its associated ductwork means the minimization of contaminants entering the indoor air, Increased efficiency of the overall HVAC system due to improved air flow, increased ability of the unit to heat and cool occupied spaces, and prolonging the life of the unit.
Wanna dig deeper? Our commercial air duct cleaning page contains detailed descriptions, before and after photos, and videos of our commercial duct cleaning processes.
Many thanks to our commercial project manager Ben S for lending his expertise to this article.