A picture certainly does say a thousand words. Dirt is the death of HVAC equipment. That’s because dirt restricts air flow and restricted air flow makes fans work harder to push air through the system. If less air is being pushed than specified by the manufactured specifications, compressors also have to work doubly hard to cool the air passing across the evaporator coil. Any component that is overworked like this requires extra electricity to run. The extra amperage heats up components, sometimes to the point of failure.
That’s all it takes is a little dirt and the two major components of your air conditioner are put in jeoporday of failing. And even if they don’t fail you are going to pay a lot more in electrical bills.
This points to the extreme importance of regular maintenance of commercial air conditioners and heaters. You will pay so much more in repairs and utility bills than you will in regularly maintaining your equipment. And ask your contractor if they are cleaning the return air grills. It is a frequently overlooked item. In our regular maintenance schedule for commercial building we recommend quarterly filter changing and annual cleaning of the return air grills.