Performed 3 system cooling maintenance. Systems are from 2016 and are gas. Basement unit is hardly used. I checked amps, capacitors, filters, electrical, drains, cleanliness, and safeties. The systems are performing well with some needed protections and cleanings. The main unit and master bedroom units have some build up in the duct work that could lead to excessive dust build up on the internal parts: blower motor and evaporator coil. This could cause damage to the evaporator coil, blower motor, and compressor. The units do not have surge protection. The units are 2016 with a possible 1 year left of warranty. The compressor needs to be protected due to EPA guidelines that would lead to system replacement if failure occurs.