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Unitary Air Conditioner Cost Estimator

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Corrections to Tested Performance: Capacity and Condenser Power

  • DOE-2 Correction Curves:
    • Total Gross Capacity = TGCrated * fTC(ODB, EWB)
    • Condenser Power = CPrated * fTC(ODB, EWB) * fEIR(ODB, EWB)

Discussion:

Because of the binned analysis in the RTU Comparison Calculator, there is need to determine equipment performance at ambient conditions other than the ARI rating conditions (ODB=95 oF, EWB=67 oF). The DOE-2 cooling correction curves allow performance to be estimated at other environmental conditions. These corrections are functions of outside dry bulb temperature (ODB) and entering (mixed air) wet bulb temperature (EWB).

In making corrections to system power draw, the RTU Comparison Calculator makes use of two of these DOE-2 correction functions. In DOE-2 reference literature, these can be identified in the commercial package DX group of functions:

COOL-CAP-FT: correction to the rated total gross cooling capacity

COOL-EIR-FT: correction to cooling energy input ratio (EIR = Btuin/Btuout)

The RTU Comparison Calculator's correction function for condenser power draw is derived as the product of these two functions.

The system performance calculation page serves to demonstrate the correction methods described on this page and the next. The results of corrections to total gross capacity are seen in columns with header names "TCap (Gross)."