DOE-2 Reference Manual Version 2.1 - DOE2.com

This is true for all the SYSTEM-TYPEs listed in the previous paragraph, evenSZRH and PSZ, which normally cool and reheat the air sequentially. Ifreheating is not available during dehumidification, the supply air temperatureis still reset toward MIN-SUPPLY-T and overcooling of the ZONE(s) could result.For SYSTEM-TYPE equals MZS, DDS, or PMZS, the value specified forMAX-HUMIDITY does not override the hot deck temperatures (specified usingHEAT-CONTROL)a:s-a means of forcing more air through the cold deck· to obtainincreased dehumidification.The program will not force the cooling coil (or cold deck) to performbeyond its dehumidification capability. The cooling coil temperature will bedropped to MIN-SUPPL Y-T, but not below MIN-SUPPLY-T. If the value ofMAX-HUMIDITY cannot be maintained when the coil is operating at MIN-SUPPLY-T,the program will calculate the MAX-HUMIDITY corresponding to the coolingcoil's performance at MIN-SUPPLY-T. If it is not possible to dehumidify downto MAX-HUMIDITY, at design conditions,. a diagnostic message will be printedfor the user.The user should exercise caution when specifying a value forMAX-HUMIDITY, because the program does not know the user's needs and, hence,cannot check the reasonableness of the specified value. As long as the valueis between 30 per cent and 80 per cent R.H. (the program limits forMAX-HUMIDITy), the program will accept and use the value. An unnecessarilylow value for MAX-HUMIDITY can be very wasteful. The user is urged to employgood engineering judgement by not specifying a MAX-HUMIDITY any lower thannecessary.Fan Heat:The heat from the supply air fan may be added to the air stream eitherbefore or after the coils, depending upon the value specified forFAN-PLACEMENT. If FAN-PLACEMENT = DRAW-THROUGH, the supply fan heat is addedafter the coils. If FAN-PLACEMENT = BLOW-THROUGH, the supply fan heat isadded before the coils. The heat of the optional return air fan is alwaysadded to the return air stream, after the plenum and before the system-levelexhaust (relief). The heat from the optional exhaust air fan(s), either atthe SYSTEM level or the ZONE level, is assumed to be lost from the building inthe exhausted air.Baseboard Heaters:If the user chooses to use the optional thermostatically-controlled baseboardheaters (BASEBOARD-CTRL = THERMOSTATIC), he should be aware that theother heating device(s) in the SYSTEM and ZONE, regardless of SYSTEM-TYPE, donot start to add heat until the baseboard heaters are at maximum output. Whenbaseboard heaters are reset by outdoor temperatures (BASEBOARD-CTRL =OUTDOOR-RESET), their heat contribution to the ZONE occurs irrespective of theZONE temperature control. See Sec. B.6 of this chapter for more informationon baseboard heaters.I V.114 (Revised 5/81)