DOE-2 Reference Manual Version 2.1 - DOE2.com

design routine will change MAX-SUPPLY-T until the equation is consistent. Thischange will always be made in a downward direction, never upward.If the user specifies a value for AIR-CHANGES/HR and/or CFM/SQFT, thedesign routine will accept them, unless either (D) or (E) is made inconsistentby them. In this case, the specified value{s) will be changed to make equation(E) consistent; that is, the cooling equation will be made consistent becauseit has priority over the heating equation (O). If there is no peak cool ingload, the CFM will be determined by equation (D). The other possibility ofthese values being changed occurs in the central systems when SUPPLY-CFM isalso entered (this is discussed later).If any of ASSIGNED-CFM, CFM/SQFT, or AIR-CHANGES/HR are entered along withMAX-HEAT-RATE (i.e., heat addition rate) or MAX-COOL-RATE (i.e., heat extractionrate), there is a possibil ity that equation (B) or (C) is violated. Inthis case, MAX-HEAT-RATE or MAX-COOL-RATE is altered to make the equation{s)consistent. If only MAX-HEAT-RATE and MAX-COOL-RATE are specified, i.e., noair quantity is specified at the zone level, the design routine will take thevalue of CFM from (B) or (C), with the larger CFM from (B) or (C) takingprecedence. If the user has also specified HEATING-CAPACITY orCOOLING-CAPACITY for zonal systems, again an inconsistency can arise with (D)or (E). The CFM just computed from (B) or (C) may not fit with the values ofthe capacities. In this case the capacities win out over the heating/coolingrates. In other words, MAX-HEAT-RATE and MAX-COOL-RATE should only be usedwhen no other sizing information is given and the user wants to override themaximum heating and cooling loads from LOADS.The above discussion must be modified slightly for variable air volumesystems, since there is now a distinction between the CFM for cooling and theCFM for heating. Based on the MIN-CFM-RATIO and the user's choice, or not, ofreverse-action thermostat strategy, there will be for each zone a maximum CFMand CFMH, where the latter describes the cfm for heating-.For central constant volume systems the maximum air capacity of the fansis taken as the sum of the zone cfm's (CFM) determined above, unless the userhas entered SUPPLY-CFM. Again, unless the user has entered SUPPLY-CFM, theair capacity for variable air volume systems will be calculated from equationslike (B) and (C), where DESIGN-HEAT-T and DESIGN-COOL-T are replaced by theiraverages over all the zones and the coincident building loads from LOADS areentered for the extraction rates. For a number of systems (see theApplicability Tables) this method of sizing the central fans may be overriddenwith the use of the SIZING-OPTION keyword, where the code-word NON-COINCIDENTsums the peak load CFMs for the individual zone loads, while the code-wordCOINCIDENT uses the building coincident load (block load).If SUPPLY-CFM is entered and if all the zones were given ASSIGNED-CFMs, itis assumed that the user intends the values to remain as entered. If not allthe zones are given an ASSIGNED-CFM, the cfms of the remaining zones arereapportioned to balance the zone air with the SUPPLY-AIR.I V. 301 (Revised 5/81)