DOE-2 Reference Manual Version 2.1 - DOE2.com

Example:Variable Volume Cooling I Constant Volume Heating with Program CalculatedCold and Hot Deck Temperatures for MZS, DDS, and PMZS(with COOL-CONTROL = WARMESTand HEAT-CONTROL = COLDEST)Note: This is not a commonly used strategy for actual HVAC systems. Theexample, howeve~serves to demonstrate the program's capability to simulatevariable volume and variable temperature with dual duct systems.This control strategy produces a variable volume flow of air entering theZONE for cooling and a constant volume flow of air for heating. This strategyuses two thermostat set points, which are specified via COOL-TEMP-SCH and HEAT­TEMP-SCH. The hourly cold deck temperature and air flow rate vary for differentcalculated ZONE temperatures in the cooling THROTTLING-RANGE(COOL-CONTROL = WARMEST). The cold deck temperature is automatically set bythe program to cool the ZONE with the highest relative temperature in itscooling THROTTLING-RANGE (COOL-CONTROL = WARMEST). The hourly hot decktemperature and air flow rates (through both the hot deck and cold deck) varyfor different ZONE temperatures in the heating THROTTLING-RANGE (HEAT-CONTROL= COLDEST). The hot deck temperature is adequate to heat the ZONE with thelowest relative temperature in its heating THROTTLING-RANGE (HEAT-CONTROL =COLDEST). It is of importance to note that when specifying MZS, DDS, or PMZSwith COOL-CONTROL = WARMEST and HEAT-CONTROL = COLDEST, both cold and hot decktemperatures are subject to ch ange in the same hour. Fig:TV.5 ill us tra tesgraphically this concurrent resetting of the cold deck temperature and the hotdeck temperature. The following description is based upon a system with dualdampers that are not physically linked to each other, that is,.they each havetheir own controller. To obtain the same physical results, the user mayalternatively employ a mixing box with a variable volume output.Cold Deck Air Flow and Temperature for the WARMEST ZONE - At calculated ZONEtemperatures above the cooilng THROTTLING-RANGE, the alr flow rate in the coldduct is at the maximum. As the calculated ZONE temperature drops from the topto the midpoint of the cooling THROTTLING-RANGE, the air flow rate in the coldair duct drops from the maximum to the MIN-CFM-RATIO. As the calculated ZONEtemperature continues to drop from approximately the midpoint to the bottom ofthe cooling THROTTLING-RANGE, the air flow rate remains at the MIN-CFM-RATIO.Simultaneously, the cold deck temperature is raised linearly such that at thebottom of the cooling THROTTLING-RANGE the cooling is completely turned off.As the calculated ZONE temperature drops across the deadband, the air flow rateremains at the MIN-CFM-RATIO and the air, a mixture of return and outside air,is uncooled. As the temperature continues to drop from the top to approximatelythe midpoint of the heating THROTTLING-RANGE, the air flow rate in thecold duct decreases linearly from MIN-CFM-RATIO to zero (this is accompaniedby an opposite action in the hot air duct). The air, however, is not beingcooled. For calculated temperatures below the midpoint of the heatingTHROTTLING-RANGE, the air flow rate in the cold duct remains at zero.IV.122 (Revised 5/81)