Hvac tune up in Lilburn, Georgia. One system. Changed filter. Tested mechanical and electrical components. Found excessively high static pressure due to not enough return duct. Found system with no water safety whatsoever and it is there not up to code. System has no surge protection. Recommend installing surge protection to protect equipment from power surges. Installed filter grill in return of system and installed water safety switch. System is heating at this time.