Frank is a maintenance worker at Grey Sloan Memorial Hospital.
During the super storm, the power kept flickering at the hospital, despite their backup generators. Frank was responsible for taking care of the problem. According to Richard, a similar thing had happened in 2006 when there was air in the fuel system and Frank told Richard it would never happen again. Frank went to figure out what was wrong.
After finishing his surgery, Richard went down to the basement to figure out what was wrong and why Frank hadn't yet restored the power. He found Frank slumped up against a wall after having had a heart attack. Richard performed CPR and then sent Frank upstairs for a workup. As he was being wheeled upstairs, Frank told Richard that he was right and there was air in the fuel system. He fixed the problem and just had to flip the transfer switch.
Frank works in maintenance at Grey Sloan Memorial Hospital. As he was said to have worked there since at least 2006, that means he also worked at Seattle Grace Mercy West Hospital and Seattle Grace Hospital.