ZONE HEATING-COOLING SEQUENCING IN MULTIZONE LOGIC 18# 13# 8# 7.5# 2# THERMOSTATS’ DEMAND SIGNALS COLD DECK HOT DECK HOT DECK HOT DECK HOT DECK COLD DECK COLD DECK COLD DECK COLD DECK HOT DECK The zone thermostat with the greatest requirement for cooling modulates the free cooling in the winter and the mechanical cooling in the summer, to varying degrees, just enough to keep the served areas within the comfort zone. The zone demanding cooling does not mix any hot deck air with the air sent to that zone during this mode of operation, allowing the least amount of cooling, in the cold deck, to maintain comfort conditions. At least minimum ventilation is maintained during all occupied times. The zone thermostat with the greatest requirement for cooling modulates its zone dampers to completely close its hot deck and completely open its cold deck. At this point the cooling is still not active. At least minimum ventilation is maintained during all occupied times. WARMEST THERMOSTAT DETERMINES COOLING DEGREE COOLEST THERMOSTAT DETERMINES HEATING DEGREE TYPICAL OF ALL ZONES All zone thermostats are modulating their zone hot deck and cold deck dampers within their spring range; therefore, all are within one Fahrenheit degree of set point. The hot deck is maintained at minimum heat and the cold deck for summer holds the cooling off and for winter the free cooling is off. At least minimum ventilation is maintained during all occupied times. WARMEST ZONE WARMEST ZONE COOLEST ZONE COOLEST ZONE The zone thermostat with the greatest requirement for heating modulates its zone dampers to completely close its cold deck and completely open its hot deck. At this point the heating is still not active. At least minimum ventilation is maintained during all occupied times. The zone thermostat with the greatest requirement for heating modulates the hot deck heating valve, to varying degrees, just enough to keep the served areas within the comfort zone. The hot deck is also limited by the outside air temperature and sometimes the return air temperature. The zone demanding heating does not mix any cold deck air with the air sent to that zone during this mode of operation, allowing the least amount of heating, in the hot deck, to maintain comfort conditions. At least minimum ventilation is maintained during all occupied times. 5.39
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