Carrier 50KC04-06 Service And Maintenance Instructions

48ENTHALPY SETTINGSWhen the OA temperature, enthalpy and dew point are below therespective set points, the Outdoor Air can be used for economiz-ing. Figure 62 shows the new single enthalpy boundaries in theW7220. There are 5 boundaries (set points ES1 through ES5),which are defined by dry bulb temperature, enthalpy and dewpoint.Refer to Table 18 for ENTH CURVE set point values.The W7220 calculates the enthalpy and dew point using the OAtemperature and humidity input from the OA enthalpy sensor.When the OA temperature, OA humidity and OA dew point areall below the selected boundary, the economizer sets the econo-mizing mode to YES, economizing is available.When all of the OA conditions are above the selected boundary,the conditions are not good to economize and the mode is set toNO.Figure 62 shows the 5 current boundaries. There is also a high lim-it boundary for differential enthalpy. The high limit boundary isES1 when there are no stages of mechanical cooling energized andHL (high limit) when a compressor stage is energized.Fig. 62 — Single Enthalpy Curve BoundariesECONOMIZINGAVAILABLENOT AVAILABLEENTHALPYRA HUM (%RH)RA TEMPTEMPERATUREABSOLUTE HUMIDITYES5 ES4 ES3 ES2 ES1 HLP1(T,RH)P2 (T,RH)SINGLE ENTHALPYDUAL ENTHALPYHIGH LIMITTable 18 — Single Enthalpy and Dual Enthalpy High Limit CurvesENTHALPYCURVETEMP. DRYBULB (F)TEMP.DEWPOINT (F)ENTHALPY(btu/lb/da)POINT P1 POINT P2TEMP. (F) HUMIDITY(%RH) TEMP. (F) HUMIDITY(%RH)ES1 80 60 28.0 80 36.8 66.3 80.1ES2 75 57 26.0 75 39.6 63.3 80.0ES3 70 54 24.0 70 42.3 59.7 81.4ES4 65 51 22.0 65 44.8 55.7 84.2ES5 60 48 20.0 60 46.9 51.3 88.5HL 86 66 32.4 86 38.9 72.4 80.3