DOE-2 Reference Manual Version 2.1 - DOE2.com

ix.Example Control Strategies for SYSTEM-TYPE Equals SZCIIf the user has not done so, he should read the General subsection (Sec.B.5.a of this chapter) before continuing here. That subsection containsinformation that is appropriate to this SYSTEM-TYPE, the Ceiling InductionSystem.In this SYSTEM-TYPE a single supply air duct provides treated air to eachZONE. There are two major control strategies that are defined by theselective specification of values for the keywords COOL-CONTROL,COOL-TEMP-SCH, HEAT-TEMP-SCH, THERMOSTAT-TYPE, and REHEAT-DELTA-T.These control strategies are listed in Table IV.29.These control strategies all involve two ZONE thermostat set points, onefor cooling and one for heating. The desired set points are specified,respectively, with the keywords COOL-TEMP-SCH and" HEAT-TEMP-SCH (plus theirassociated SCHEDULEs).The user may specify zone (reheat) coils in the air duct (seeREHEAT-DELTA-T in the SYSTEM-TERMINAL subcommand).Both the major control strategies for this SYSTEM-TYPE have variable airvolume flow, at the SYSTEM level, for cooling. The flow rate of air enteringeach ZONE, however, is constant due to the action of the ZONE induction box.The hourly temperature of the cooling supply air (specified via COOL-CONTROLin the SYSTEM-CONTROL subcommand) entering each induction box is often colderthan required to meet the cooling needs of the ZONE. During these times, thisflow of cooling air is reduced. The volume of cooling supply air entering theinduction box may vary hourly from 100 per cent down to 50 per cent of theZONE design cooling flow rate (that is, the amount of air required to meet theZONE peak cooling load). The balance of the air is induced from the plenumabove the room ceiling. This induced air is intended to reduce the coolingability of the primary air. The induced air flow rate is limited to a maximumof 50 per cent of the ZONE design cooling flow rate. In summation, variablevolume cooling air is mixed with the variable volume induced warm air to producea constant volume supply air flow to the ZONE.Air flow in the supply duct during the heating mode is constant at 50 percent of the maximum. The final temperature of the air stream is controlled atthe ZONE level with the keyword HEAT-TEMP-SCH. As the calculated ZONEtemperature drops from the top to the bottom of the heating THROTTLING-RANGE,the air flow into the ZONE is 50 per cent primary air and 50 per cent inducedwarm air. The zone coil heating output rate increases linearly from zero atthe top of the heating THROTTLING-RANGE to maximum at the bottom of theheating THROTTLING-RANGE.This system type is normally used for interior zones only.are no reheat coils, although baseboards are sometimes used.Often thereIV.160 (Revised 5/81)