Effect of data period-of-record on estimation of HVAC&R design temperatures

The variability of the estimation of design conditions for 16 North American locations was studied by comparing the difference in design conditions obtained from long-term (30 year) period-of-record (POR) data to those determined from subsets of the long-term POR data. The dry-bulb, dew-point, and wet-bulb temperature design conditions were analyzed for 1- to 15-year POR weather data subsets. The analysis demonstrated that if the estimate of the design values were determined using a one-year POR the average of the annually determined design heating values would be slightly warmer and the design cooling values would be slightly cooler than using the 30-year POR. However, the range of differences was considerable and demonstrates the masking of variation in design temperatures caused by determining averages for different locations.