We managed to fix the issue by ordering a new HVAC system.
I worked at maintenance at the prestigious office skyscraper in town. I was responsible to ensure all mechanical units that served the building were functioning at 100 percent all the time. I took my work very seriously because it also paid very well. I also thoroughly enjoyed the job which entailed keeping up with the regular quality AC service on the cooling units that were in the building. There were several cooling equipment within the building and all were used mostly to help with indoor comfort. One hot summer morning, I noticed that the commercial air conditioning system was smoking and making unusual sounds. I first confirmed that the HEPA filter and the air duct were both clean and free from any blockages. I contacted the cooling specialist when I could not resolve the issue. Though working, the zoned HVAC unit was not at an optimal level. By the time the cooling workman came, the central air conditioning was literally on fire and after putting the fire out with the extinguishers, we switched off the unit using the wireless thermostat. While all this was happening, the staff and other businesses were not aware but as soon as we switched off the unit, I started getting complaints. We managed to fix the issue by ordering a new HVAC system. It was installed in a record time of three hours of which 1 hour was the lunch period. By the end of that day, we had a new system and I made sure to log in to the HVAC services that were due. I was glad the issue did not escalate to burn down the entire building, thanks to the ever-present extinguishers and quick thinking to switch off the unit.