This paper summarizes the final results of the research done on the ASHRAE project entitled “HVAC System Dynamics and Energy Use in Existing Buildings.” This project was sponsored by TC 4.6, (formerly TG) on building operation dynamics. The overall objective of the project was to determine operating strategies for HVAC systems that incorporate system dynamics and interactions and potentially reduce energy use. The previous paper on this project (Hackner et al. 1984) reported on the results of short term tests of equipment dynamics and the simulation model development.

In this paper, the use of the model to determine an optimal control strategy is described. The optimal strategy is then implemented via simulation of the HVAC system, and the effects of system parameters are explored. The current HVAC operating strategy, the optimized strategy, and a constant set point strategy were compared. An energy savings of 8.7% is possible using the optimized strategy compared to the current control strategy. The constant set point strategy used 9% and 19% percent more energy when compared to the current and optimized strategies, respectively.

The effect of the time between control decisions was evaluated. A 3 to 4% energy savings was possible for a system operating under dynamic control as opposed to a system in which control decisions were made on an hourly basis.