DOE-2 Reference Manual Version 2.1 - DOE2.com

COOL-CTRL-RANGEMIN-UNLOAD-RATIOMIN-HGB-RATIOfunction of the entering wet-bulb temperature (independentvariable) and entering dry-bulb temperature (independentvariable. The bi-linear or bi-quadratic equation must beinput to the program and U-named in a CURVE-FITinstruction. The equation should be normalized so that atrated conditions its value is 1.0.is the throttling range of the cooling coil controller andit is represented by Tmax-Tmin where T ax is thetemperature of the coil when it is ful~y loaded and Tminis the temperature of the coil when it is fully unloaded.is the point, expressed as a part load ratio (PLR), atwhich compressor unloading stops and hot gas bypass orcycling begins (see M-U-R in Fig. IV.26). TheCOOL-EIR-FPLR applies in the range of PLR's betweenMIN-UNLOAD-RATIO and 1.0, that is, the range designated as"Unloading" in Fig. IV.26.is the point, expressed as a part load ratio (PLR), belowwhich hot gas bypass stops and unit cycling begins. Belowthis point the unit cycles on and off to meet the load.MIN-HGB-RATIO is always equal to or less thanMIN-UNLOAD-RATIO (see M-H-R in Fig. IV.26).When,(M-U-RJsPLRsIO,no hotgas by-pass occurs (coil is notfully loadedJ(M-H-RJsPLR«M-U-RJ,hot gas by-pass occursI.0O.Os PLR< (M-H-RJ, coil cycles on and off, as requiredthat is,No Load(PLR=OJ M-H-R M-U-RDesign arFull Load(PLR=IO)~-----l------+--------';OO"Cycling Bypassing UnloadingCOOL-EIR-FPLRNote:If (M-U-R) ; (M-H-R), there is no hot gas bypasscapability, and the unit moves from unloading immediatelyto cycling as the PLR drops below this ratio. If (M-U-R) ;(M-H-R) ; 1.0, the unit does not unload and cycles fromfull load down to zero load.Fig. IV.26.Cooling coil operating strategy.IV.248 (Revised 5/81)