Without a filter, the condensate drain will not be able to drain moisture from the air conditioning unit. This will result in condensation building up in the Freon tube. Condensation will begin to drip down the tray, causing water damage to the entire system. The short answer is yes, your HVAC system can operate without a filter.
However, just because you can doesn't mean you should. Running your HVAC unit without a filter is probably OK for a short period of time, but continuing to do so for more than six hours is already delaying it. Unless you want your system to blow dirty air into your home or office and you also run the risk of damaging the unit, it is not advisable to run the system without a filter. Running the air conditioner without a filter will prevent the condensate drain from draining accumulated moisture from the air conditioner. Eventually, excessive condensation moisture buildup in the Freon tubing causes water to leak and can damage the entire system.
The longer you leave your air conditioner running without a filter, the more likely you are to have problems with indoor air quality. As a result, you or others in your household may experience increased symptoms of allergy, respiratory problems, eye irritation, or irritation of the nose and throat.
What are the Risks of Operating an AC Without a Filter?As a general rule, it's never a good idea to operate your air conditioner or HVAC system without an air filter in place. Additional dirt and debris that passes into the air conditioning system due to the lack of an air filter can reach the condensate drain (where it's not supposed to be) and clog the drain. That said, running your air conditioner without a filter for more than 6 to 8 hours can cause serious damage to your air conditioning system and significantly reduce the air quality in your home. When you operate your air conditioner without a filter, dust is absorbed into the indoor air conditioning unit and settles on a part of that system called evaporator coils.
Without a filter in place, these contaminants can travel freely through the ducts and can settle there, which can also negatively affect health due to worsening indoor air quality. The air conditioner draws air from the indoor environment and removes heat from it before returning it to the room. The function of the air cleaner, together with the compressor motor and evaporator coils, is to prevent air pollutants from entering the air conditioner. While some homeowners can clean or replace their air conditioning filters on their own, there's no shame in letting a professional do the work for you. Your AC filter is usually constructed of spun fiberglass material or of pleated paper or cloth within a frame.
An air conditioning system that works without a filter will have a huge negative impact on indoor air quality, possibly even causing the spread of diseases or an increase in allergic reactions.