. To be designated as a Mitsubishi Diamond Contractor, a dealer must achieve an exceptional level of training, expertise, and customer satisfaction. We'll use your zip code to match you with highly trained contractors in your area who can help you find your perfect match - from understanding your desired application to sizing the equipment to installation and service. Call Today: (610) 377-1098. “For the last two and a half years, we’ve been working to establish a tiered program,” said John Wright, sales manager of contractor development, Mitsubishi Electric US, Inc.