One of our clients had a building management system (BMS) which had become outdated, making it very difficult to find replacement parts or service technicians who were qualified to work on it. The client wanted to upgrade their system to gain the benefits and cost savings of a modern BMS, but due to budget restrictions, had to complete the replacement in phases. We designed an installation plan that allowed both systems to run simultaneously until the last rooftop unit was under the control of our state of the art control and automation system. The client also wanted more control over their two-year-old rooftop units, so we designed a brand new main control board (along with program) to replace the factory model. By re-designing the main board we were able to control, monitor and trend items that could not be done through the original roof top control system.