## 2 Current Methodology (ASHRAE 90.1-2019 Standard)
It is appropriate that in a place of thermal load and air supply conditions constant at 8760 h, the priority is the efficiency in Net Sensible COP. However, although there is no variation internally, there is an external factor in the equipment: the temperature of the air inlet in the condenser constantly changes, implying a positive or negative change in the performance of the air conditioning equipment. This temperature variation has a relevant impact on the performance of the inverter or digital compressor equipment type. The integrated part load value (IPLV) is a performance characteristic developed and used in AHRI's methodology. This methodology considers variable air intake temperature in the condenser and variable thermal load based on the average temperature of the 29 major cities in the United States of America (U.S.A.). IPLV is a methodology in which COP is measured in partial loads. IPLV is a parameter to consider even in chillers for data centers. Its parameters are described in AHRI 550/590-2015 [12]. These parameters are in accordance with Equation (1) and described in Table 6.  
\[\text{IPLV (or NPLV)}=0.01\cdot\text{A}+0.42\cdot\text{B}+0.45\cdot\text{C}+0.1 2\cdot\text{D} \tag{1}\]  
where,  
A: COP at 100% capacity, (kW/kW). B: COP at 75% capacity, (kW/kW). C: COP at 50% capacity, (kW/kW). D: COP at 25% capacity, (kW/kW). \begin{table}
\begin{tabular}{c c c} \hline \hline
**System Type** & **Fluid Condition** & **Test Condition** \\ \hline Air-cooled units & Entering outdoor ambient DBT (\({}^{\circ}\)C) & 35.0 \\ \hline \multirow{3}{*}{Water-cooled units (typically connected to a common glycol loop)} & Entering water temperature (EWT) (\({}^{\circ}\)C) & 28.5 \\ \cline{2-3}  & Leaving water temperature (LWT) (\({}^{\circ}\)C) & 35.0 \\ \cline{2-3}  & Water Flow rate (L/s) & N/A \\ \hline \multirow{3}{*}{Glycol-cooled units (typically connected to a common glycol loop)} & Entering glycol temperature (\({}^{\circ}\)C) & 40.0 \\ \cline{2-3}  & Leaving glycol temperature (\({}^{\circ}\)C) & 46.0 \\ \cline{2-3}  & Glycol Flow rate (L/s) & N/A \\ \cline{2-3}  & Glycol solutions concentration & 40\% Propylene glycol by volume \\ \cline{2-3}  & Entering water temperature (EWT) (\({}^{\circ}\)C) & 10.0 \\ \cline{2-3}  & Leaving water temperature (LWT) (\({}^{\circ}\)C) & 16.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Heat rejection/cooling fluid standard rating conditions [11]. From a macro point of view, there is an index that analyzes the conditions of free cooling, evaporative system, and variable COP in data centers: the Energy Usage Effectiveness Design (EUED), with the following characteristics (see Figure 5) [13]:  
* When the outside air temperature is below 20 \({}^{\circ}\)C and the enthalpy is below 42.7979 kJ/kg, only free cooling will be used. * When the temperature is between 15 and 24 \({}^{\circ}\)C and the enthalpy is from 42.7979 to 55.8233 kJ/kg, the evaporative system will be used. * When the temperature is above 20 \({}^{\circ}\)C and the enthalpy is over 55.8233 kJ/kg, the normal system will be used under the following conditions: 1. Air intake temperature between 24.1 and 27 \({}^{\circ}\)C, called COP1. 2. Air intake temperature between 27.1 and 30 \({}^{\circ}\)C, called COP2. 3. Air intake temperature between 30.1 and 33 \({}^{\circ}\)C, called COP3. 4. Air intake temperature above 33.1 \({}^{\circ}\)C in any condition, called COP4. 5. If a geothermal temperature is available, it will be used to determine the COP, with a differential of 4 \({}^{\circ}\)C of the geothermal temperature.