Choosing a contractor to install or replace the heating and cooling system (HVAC) in your home may be the most important and difficult step in the process. Ask prospective contractors for recent references. If you are replacing your central air conditioner, tell your contractor what you liked and did not like about the old system. If the system failed, ask the contractor to find out why. The best time to fix existing problems is when a new system is being installed.

When designing your new air conditioning system, the contractor you choose should:

• Use a computer program or written calculation procedure to size the air conditioner
• Provide a written contract listing the main points of your installation that includes the results of the cooling load calculation
• Give you a written warranty on equipment and workmanship
• Allow you to hold the final payment until you are satisfied with the new system.