... Smaller systems focus on 120/208 V, larger systems on 277 /480 V. Control systems usually step down to 24 V.Utility and campus distribution voltages are often found at 2300,4160, 72 00, and 12, 470 ... Air Conditioning,May 1 971 , pp. 75 77 .2. National Electric Code, National Fire Protection Association, Quincy, MA, 1999,revised every 3 years.Electrical Features of HVAC Systems Downloaded from ... 3 97 Chapter12Electrical Featuresof HVAC Systems 12.1 IntroductionWhile most HVAC designers will have the support of a competent elec-trical design staff, it is important...