Arrived to do a maintenance on a Bryant system vertical in closet. I cleaned and flushed the drain line with water and cleaner. I checked the electrical system. I changed the filter, 20x20x4, owner has there own filters. I recommended the following to keep the system running almost like new: The surge protector is to keep from burning up the board or electrical on the condenser. If you get high power surges or lightning strikes in the area it may burn up the electrical on the condenser. The freeze protector is to keep from freezing up the coil in the air handler. If the blower fails or no air flow over the coils it will freeze the coil in the air handler. The pan treatment is to keep the algae out of the drain line and pan. The Uv light is to keep the biological growth out of the air handler. And the air that you breath every day. The system is working great at this time. Thanks for using air now for all your air conditioning needs. Arrived to do a maintenance on a Bryant