MULTIZONE ZONE CASE STUDY The intent of this case study is to allow an understanding of a significant problem relating to the Heating, Ventilation and Air Conditioning (HVAC) industry. The issue addressed involves simultaneous heating and cooling, due to poor design, installation and commissioning of control systems. This paper's intent is promotion of a thorough understanding relating to the problem, enabling one to address similar situations as they are encountered. This case study reflects a relatively simple conservation circuit. More complicated circuits may assess the probability of a thermostat demand signal being false by looking at the outside and return air temperatures, as well as the thermostats’ demand signals. A significant quantity of greenhouse gas (GHG) enters our atmosphere directly relating to poor control arrangements as illustrated in this case study. This case study is presented in these steps: (1)- The fan system is considered manual as illustrated in drawing one. What are you manually controlling? What are your target conditions? How would you logically adjust the operations? (2)- The original design is illustrated in drawing two. We identify the design problems. (3)- The conservation circuit is illustrated in drawing three. (4)- Graph #1 illustrates the original design heating and cooling function performance relative to varying outside air temperatures. (5)- Graph #2 illustrates a comparison of original design cooling levels and actual cooling requirements of the warmest zone on the system. (6)- Graph #3 illustrates a comparison of the original design heating levels and the actual heating requirements of the coolest zone on the system. (7)- Remember, if the control system is not making the same common sense, device poitioning decisions as an intelligent person, with identical information input, there is something wrong with the control system! 8.80
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