When your duct system is too small to ensure that your air conditioner has enough air, your system's performance will drop. This is because, with the amount of air getting into the system being limited by the ducts, your system will be functioning at half-capacity. It won't cool as much air as it can, and your system will take longer to cool your office space. It will also end up using way more energy, increasing your energy bills.
Undersized duct system and evaporator coil icing
The fact that the air conditioner is designed to specifically handle a given amount of air at any given time, restricting airflow can lead to air conditioning complications. One of the most common ones is evaporator coil icing. This is a condition that arises as a result of temperatures in the evaporator coil dropping to below freezing point. As a result, ice deposits form on the coils of the air conditioner. Because ice usually allows the air conditioner to hoard a lot of the condensate, this also increases the risks of air conditioner water leaks. This, and the fact that ice also insulates the evaporator coil, makes solving this problem imperative.
Identifying an undersized duct system
Telling whether the ducts are undersized or not is sometimes a challenge. First, compare the diameter of your ducts and that of the air conditioner's blower. If the blower's opening is way larger than that of the ducts, then you likely have undersized ducts and they are limiting the performance of your system.
Common signs of restricted airflow such as iced coils will also be useful in helping you to detect this problem. If you hear banging noises coming from the air conditioner's air ducts, your ducts are likely undersized. This is because the ducts are periodically getting collapsed because they can't replace the already-sucked air, leading to the creation of vacuums that then force the walls to collapse.
Increasing airflow in a system with undersized ducts
The most straightforward solution to an undersized duct problem is to remove the existing ducts and then replace them with larger ones. You can also solve this problem by adding more return air inlets. Although washing clogged filters will not solve the undersized duct problem, it will help make a bad situation better by reducing the obstructive nature of the filters.
Talk to your local commercial HVAC contractor to find more information.