Arrived to do a maintenance on two York PKG units. I cleaned and flushed the drain lines with water and cleaner. I checked the electrical systems. I checked the filters, 1-20x20x1 washable, 1-12x20x1 washable. Owner cleaned them before arrival. I recommended the following to keep the systems working almost like new: The surge protector is to keep from burning up the board on the system. If you get high power surges or lightning strikes in the area it may burn up the board on the system. The start assist is to help start the unit easier and last longer. The freeze protector is to keep from freezing the coils. If the blower fails or no air flow over the coils it will freeze the coils. The Uv light is to keep the biological growth out of the blower and coil areas of the unit. And the air steam that you breath everyday. The systems are working great at this time. Thanks for using air now for all your air conditioning needs.