Cold weather and heating system design

The first step in sizing heating equipment, according to the American Society of Heating, Refrigerating and Air-Conditioning Engineers' (ASHRAE) recommended general procedures (ASHRAE, 1985), is to select outdoor design weather conditions. Design winter dry bulb temperatures have been tabulated by ASHRAE (1985) for more than 700 U.S. stations. The ASHRAE Weather Data Committee, TC 4.2, is evaluating the current design data set to determine whether or not it adequately represents the weather events that affect the sizing of heating equipment. Tabulated winter design temperatures are based only on the distribution of winter hourly dry bulb temperatures over 15 years. This article provides both qualitative and probabilistic descriptions of cold outbreaks for four stations.