Thermo Fisher Scientific will add 110 workers to its manufacturing plant over the next seven months to help build a new line of temperature controls for scientific equipment. The jobs will pay an average of $40,800 and will help lower the county’s unemployment rate, which stood last month at 8 percent, said K. Ray Bailey, a Buncombe County commissioner and chairman of the Economic Development Coalition for Asheville-Buncombe County. “We are working with existing companies, trying to grow our own economy,” Bailey said.