DOE-2 Reference Manual Version 2.1 - DOE2.com

This SYSTEM-TYPE utilizes a two set point thermostat. The desiredcooling and heating set points are specified, respectively, with the keywordsCOOL-TEMP-SCH and HEAT-TEMP-SCH (plus their associated SCHEDULEs). If outsideventilation air is specified, the supply air fan operates continuously,assuming the FAN-SCHEDULE is turned on. If outside ventilation air is notspecified, the fan cycles on and off with the refrigeration compressor, again,assuming the FAN-SCHEDULE is turned on.The working fluid in the pipe loop absorbs heat from those heat pumps thatare operating in the cooling mode and gives up heat to those heat pumps thatare operating in the heating mode. When the total cooling demand exceeds thetotal heating demand, the fluid temperature increases. If the fluidtemperature exceeds MAX-FLUID-T (SYSTEM-FLUID subcommand), the excess heat isdissipated to the atmosphere through a cooling tower or through other coolingequipment specified in PLANT. When the total heating demand exceeds the totalcooling demand, the fluid temperature decreases. If the fluid temperaturedrops below MIN-FLUID-T (SYSTEM-FLUID subcommand), heat is added to the fluidby a boiler, or other heat source, to maintain the fluid temperature atMIN-FLUID-T. No heat is added to or rejected from the fluid when itstemperature is between MAX-FLUID-T and MIN-FLUID-T. When this occurs, thesystem is merely transporting energy between the ZONEs. The cooling tower,the boiler, the pump, and the water circulation loop are simulated in thePLANT program.Examp 1 e:Assuming outside air has been specified, the heat pump and supply air fanwork as follows. The supply air fan runs continuously (even thoughFAN-CONTROL = CYCLING). At calculated ZONE temperatures above the coolingTHROTTLING-RANGE, the heat pump runs continuously, in the cooling mode. Atall calculated ZONE temperatures within the cooling THROTTLING-RANGE, the heatpump cycles on and off, still in the cooling mode. The heat pump runs justlong enough, during the simulation hour, to extract the correct number of Btusto cool the ZONE. As the calculated ZONE temperature drops across the deadband, the heat pump is turned off; the fan continues to operate, however,bringing outside air to the ZONE. As the calculated ZONE temperature dropsinto the top of the heating THROTTLING-RANGE, the heat pump cycles on, butthis time in the heating mode. At ZONE temperatures below the heatingTHROTTLING-RANGE, the heat pump runs continuously, in the heating mode.The heat from the supply air fan is added to the air flowing into theZONE. The air flow rate of each supply air fan is calculated, or specified,to match t~e needs of its ZONE. The power consumption rate per CFM of all thefans is assumed to be the same. That total fan consumption rate for all theheat pumps is specified in the SYSTEM-FANS subcommand. The energy input tothe compressor acts to increase or decrease the amount of heat rejected to orwithdrawn from the fluid loop.I V.140 (Revised 5/81)