"A HVAC system is a complicated system to install. There are many building standards and EPA standards that must be met. You must layout the duct system, determine the proper size of the ducts, and...
You need to be a "Certified Refrigeration Contractor". Visit this site to see how to obtain a contractor's license in your state. http://www.contractor-licensing.com/state-license.html
HVAC systems are very complicated to install. They must be installed by a licensed professional and inspected to ensure the system is safe and effective.