GENERAL Multizone fan systems often present the most potential benefit relative to the dollars spent on retrofit. Pages 6.44 and 6.45 illustrate savings achieved in the Durham Board of Education and the Scarborough Board of Education. We normally expect heating reductions ranging from 30% to 50% on multizone retrofits. The range depends on the condition of the system before we touch the controls. Dual duct systems with mixing boxes at the individual zones require the same logic changes as multizones. Dual duct systems are more expensive to retrofit, as the zone signals have to be run back to the main fan control panel. Multizones have the zone signals at the fan from the original installation. No two systems are completely identical. This case study illustrates the approach taken for this individual building. When applying this logic to another building, you must consider the safety of the occupants, building systems, etc. 8.89
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