As per your request, I am giving you list of the heating, ventilation, air conditioning (HVCA) online courses which you can study at home.

HVAC & Refrigeration Career Diploma
Fundamentals of HVAC Systems Self-Study Seminar
HVACR Certified Technician
Certificate Program in HVAC
HVAC Design Training

The online HVAC courses includes following topics:

HVAC fundamentals
Common installation standards
Hazardous materials and protective gear
Electric motor theory
Power distribution systems
Air circulation and quality
Thermodynamics of refrigeration
Electronic control systems
Heat transfer systems
Green HVAC technologies

Following are the institutes that offering the online HVAC courses are:

Penn Foster Career School
Penn Foster High School
Student Services Center
925 Oak Street
Scranton, PA 18515 USA
1-800-275-4410

Ashworth College
6625 The Corners Parkway, Suite 500
Norcross, GA 30092
Admissions (Enrollments) 1-800-957-5412

UC Berkeley Extension
1995 University Avenue #110,
Berkeley, CA, United States ‎
+1 510-642-4111

ASHRAE Headquarters
1791 Tullie Circle, N.E. Atlanta, GA 30329
Toll-free for Customer Service: (800) 527-4723 (U.S. and Canada only)
Phone: (404) 636-8400
Fax: (404) 321-5478