“The announcement just knocked our socks off,” said Jessie McCain, director of human resources. “We had an idea that we’d be on the list because they came down to visit us for a day, but we had no idea what our ranking was.”

To be eligible for the “100 Best Companies to Work for in America” ranking, a company had to be in business at least 10 years and have a minimum of 500 employees. The companies were rated on a 175–point scale, using the overall score on the employee survey (100 points); an evaluation of practices detailed in the inventory survey (55 points); and an evaluation of the employee comments (20 points).

Employee-owned TDIndustries originally was mentioned in the 1993 Robert Levering and Milton Moskowitz book “The 100 Best Companies to Work for in America.” Levering and Moskowitz helped Fortune compile its inaugural list.

TDIndustries is one of the nation’s largest mechanical contracting and service firms — ranking number 10 on PM’s Pipe Trades Giants. TDIndustries ranked second on the list in hydronics work.