Impacts of Variations in Air Conditioning System Set-Point Temperature on Room Conditions and Perceived Thermal Comfort

This paper describes research carried out to investigate specific features of the operation of air-conditioning systems of University buildings in Hong Kong. Changes in thermostat set points were introduced so as to investigate the impact on conditions experienced and also to determine spatial variations within the rooms. Measurements of environmental conditions were made at 5 minute intervals over a total investigation period of 6 days. Concurrently with the environmental measurements occupant surveys took place, the subjects being a group of postgraduate students. Some 912 sets of survey data were accumulated and this was used in conjunction with environmental data to compare actual and predicted sensation votes. Comparisons of sensation votes and preference votes were also carried out. Main findings were: that a significant degree of temperature variation occurred across the rooms despite the sets of controllers being used in conjunction with each other to effect changes; that the relationship between actual and predicted sensation votes exhibited a degree of variation between days even with the same occupants and that occupants tended to vote over a wider range than was predicted; and that there was a clear (as expected) inverse relationship between actual sensation and preference voting.