DOE-2 Reference Manual Version 2.1 - DOE2.com

ii. Example Control Strategies for SYSTEM-TYPE Equals VAVS, PVAVS, CBVAV, orRRFSIf the user has not done so, he should read the General subsection (Sec.B.5.a of this chapter) before continuing here. That subsection contains informationthat is appropriate to these control strategies and SYSTEM-TYPEs.In these SYSTEM-TYPEs a single supply air duct provides either hot orcold air to each ZONE. The four major control strategies that are defined bythe selective specification of values for the keywords MIN-CFM-RATIO,COOL-CONTROL, COOL-TEMP-SCH, HEAT-TEMP-SCH, THERMOSTAT-TYPE, REHEAT-DELTA-T,and BASEBOARD-CTRL are listed in Table IV.27. These control strategies allinvolve two thermostat set points, one for cooling and one for heating.All the control strategies for these SYSTEM-TYPEs have variable air volumeflow for cool ing. During the cool ing mode of operating, the air flow rate inthe air duct is automatically varied by the program, from one hour to the nexthour, in an attempt to del iver the correct amount of cold air (at the cold decktemperature specified via COOL-CONTROL) to meet the desired ZONE temperature,which is specified in COOL-TEMP-SCH. The cooling supply air volume enteringthe ZONE may vary from a minimum of MIN-CFM-RATIO to a maximum of the designcooling flow rate (that is, the ASSIGNED-CFM, and in its absence, the amountof air required to meet the ZONE peak cooling load), assuming the supply airfan is on. Air flow in the duct during the heating mode is either constant orvariable air volume flow, depending upon the value specified (or defaulted)for THERMOSTAT-TYPE. Space heating is accomplished at the ZONE level by zone(reheat) coils in the air duct, or by baseboard heaters within the ZONE, orboth.The physical method of varying the air flow for cooling is accomplishedby several different methods, depending upon the SYSTEM-TYPE specified by theuser. If the SYSTEM-TYPE equals either VAVS or PVAVS, the total SYSTEM coolingair is supplied by a variable volume fan (FAN-CONTROL: SPEED, INLET, orDISCHARGE) and the quantity of air to each ZONE is varied by a variable airvolume box (VAV Box). If SYSTEM-TYPE: RHFS and the user has specifiedMIN-CFM-RATIO less than 1.0, the cooling air is supplied by a constant volumefan (FAN-CONTROL: CONSTANT-VOLUME) and the quantity of air delivered to eachZONE is varied by a VAV box. If the SYSTEM-TYPE: CBVAV, the cooling air issupplied by a constant volume fan (FAN-CONTROL: CONSTANT-VOLUME). However, adifferent type of VAV Box is used that injects the correct amount of coolingair into the ZONE to meet the cooling load and the excess cooling air isbypassed into a ceil ing plenum that returns the excess cool ing- air to the airhandling unit.The heat from the supply air fan is added, by default, to the airdownstream from the cooling coil, unless the user specifies FAN-PLACEMENT:BLOW-THROUGH. The effect of the humidifier, if specified, is added to themixed outside and return air stream.I V.128 (Revised 5/81)