Programs in heating, air conditioning, and refrigeration technology prepare people to work on heating and cooling systems. Students learn to diagnose and test systems. They learn to install, service, and repair them. Some programs teach people to help engineers to design, develop, and use heating and cooling systems.

Some refrigerators have a butter compartment that keeps the butter from getting too cold to spread easily. Think about the layers of heat and cold that you might have on a winter's day: While it's cold outside, your furnace is keeping your kitchen warm. Inside your kitchen is a refrigerator to keep your food cold. And inside that fridge is a little compartment to keep the butter warm. These are the sorts of comforts that we expect in our homes and workplaces. And heating, refrigeration, and air conditioning technicians make them possible.

You can still learn this trade through informal on-the-job training, but employers tend to prefer you to be formally trained. You may get training in a certificate program at a vocational school, technical institute, or community college, or in the armed forces. The programs are often called HVAC (for Heating/Ventilation/Air Conditioning--sometimes R is added to stand for Refrigeration). They take from six months to two years. The quality of training programs at proprietary schools varies widely, so you may want to look for programs approved by the Accrediting Commission of Career Schools and Colleges of Technology. Some programs grant you an associate degree. These typically take two years of full-time study beyond high school. The degree may be useful if you plan to go into management later. Over 100 colleges offer this degree program.

Another entry route is to get a formal apprenticeship. A number of industry organizations offer these programs. They usually last from three to five years. You learn partly in the classroom and partly on the job.

When you train in HVAC, you learn how to design and install heating and cooling systems for residences and businesses. You learn how to estimate heating and cooling loads. You consider the size of the building, local climate, insulation, and other factors. For example, in a humid location you might slightly undersize the air-conditioning unit so that it runs more frequently. You learn how to draw and read plans and use them to make cost estimates. Systems generally use air ducts or finned pipes to distribute the heat (or remove it), so you learn to work with plumbing and sheet metal. You study the workings of the electric components, such as pumps and fans. You learn how to install and set up the electronic controls.

Of course, you must understand how to install and maintain the central units that produce the heat and coolness. When you study refrigeration, you learn how compressors, condensers, and evaporators work. You learn safe procedures for handling refrigerant gases. You also study safety concerns when you learn about heating units. You learn how to vent exhaust gases. You study local building codes that guard against the hazards of fires and gas leaks.