Horizon Services, the expansion-minded, Stanton, Del.-based home plumbing, heating, and air-conditioning service, said it has acquired two firms — Gold Medal Service in East Brunswick, N.J., and Casteel Heating & Cooling in Atlanta — with financing from Sun Capital, the Florida buyout firm that invested in Horizon in March.

Prices weren't disclosed. The purchases boost Horizon employment to more than 900, from a previous 650. Founding partners David Geiger and Mark Aitken said earlier that Sun was helping them buy family-owned companies with sales in the $10 million-a-year range. Similar businesses in other parts of the Eastern U.S. have sold for about half of annual sales — more or less, depending on repeat business and growth prospects.

Gold Medal Service, founded by Mike Agugliaro and partners in 1994, claims more than 17,000 residential customers in central New Jersey. Casteel Heating & Cooling calls itself "one of the largest services businesses in the Atlanta market" and claims growth of "more than 25 percent a year since 2012."

The two "strategic acquisitions" are "why we brought on Sun Capital as our financial partner," Aitken said in a statement. Horizon says it plans to expand the newly acquired operations with additional hires for its fleet of home service trucks and to improve training to increase repeat business.

In New Jersey, Horizon already has a center in Mount Laurel, serving customers in the state's Philadelphia suburbs; the Gold Medal addition brings it closer to New York. The combination "makes us the strongest plumbing, HVAC, and electrical provider in New Jersey," Agugliaro said in a statement.

In the Atlanta area, Horizon makes Casteel "part of something bigger" and will impose best practices to improve service, vice president John Hillis said. He is a son of founder Bob Casteel.

Unlike other brands Horizon has acquired, Gold Metal and Casteel will continue to operate under their current names.

Horizon also has regional centers in King of Prussia; Newark, Del.; Baltimore; and Hartford, Conn.

(The story has been updated to make clear that John Hillis is Casteel founder Bob Casteel's son)