## 2 Current Methodology (ASHRAE 90.1-2019 Standard)
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**2008 Classes** & **2011 Classes** & **Applications** & **Information Technology Equipment** & **Environmental Control** \\ \hline
1 & **A1** & &
\begin{tabular}{c} Enterprise servers, \\ storage products \\ \end{tabular} & Tightly controlled \\ \hline
2 & **A2** & & & \begin{tabular}{c} Some control \\ \end{tabular} \\ \hline  & **A3** & \begin{tabular}{c} Data center \\ \end{tabular} & \begin{tabular}{c} Volume servers, \\ storage products, \\ personal computers, \\ workstations, \\ laptop, \\ printers \\ \end{tabular} & \begin{tabular}{c} Some control, \\ use of free cooling \\ techniques when \\ allowable \\ \end{tabular} \\ \hline  & **A4** & & \
\begin{tabular}{c} Office, \\ home, \\ transportable \\ environment, etc. \\ \end{tabular} & Personal computers, \\  & B &
\begin{tabular}{c} Workstations, \\ laptops, \\ printers \\ \end{tabular} & Minimal control \\ \hline
4 & C & \
\begin{tabular}{c} Point of sale, \\ industrial, \\ factory, etc. \\ \end{tabular} &
\begin{tabular}{c} Point of sale equipment, \\ ruggedized controllers or computers, \\ PDAs \\ \end{tabular} & No control \\ \hline \hline \end{tabular}  
\end{table} 
Table 2: Classes for certain characteristics of data center enclosures [9]. A2--Generally a technological production environment or an office or a laboratory with some control over environmental parameters. They are locations that shelter small racks; they can be personal servers or workstations. The values of return dry-bulb temperature (DBT) and dew-point temperature (DPT) of 29 and 11 \({}^{\circ}\)C, respectively (see Table 3), are recommended for Class 2. These values are not recommended for Class 1, but they could be allowable. It is also important to note that a return temperature does not mean the intake of air in the rack, which will certainly be at a lower temperature. The parameters and methodologies to arrive at the values of ASHRAE 90.1-2019 are specified in AHRI 1361-2017. The air supply parameters of Table 4 of the standard of the Air-Conditioning, Heating, and Refrigeration Institute (AFRI) corroborate with ASHRAE 90.1-2019. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Mounting Locations** & **Standard Model** & **Cooling (Return Air DBT/DPT) (\({}^{\circ}\)C)** & **Humidification (Return Air DBT/DPT) (\({}^{\circ}\)C)** \\ \hline Ceiling mounted unit & \begin{tabular}{c} Ceiling mounted \\ unit ducted \\ \end{tabular} & 24.0/11.0 & 24.0/5.6 \\ \hline \multirow{4}{*}{Floor mounted unit} & \begin{tabular}{c} Upflow unit \\ nonducted \\ \end{tabular} & 24.0/11.0 & 24.0/5.6 \\ \cline{2-3}  & \begin{tabular}{c} Upflow unit ducted \\ \end{tabular} & 29.5/11.0 & 29.5/11.0 \\ \cline{2-3}  & \
\begin{tabular}{c} Downflow unit \\ \end{tabular} & 29.5/11.0 & 29.5/11.0 \\ \cline{2-3}  &
\begin{tabular}{c} Horizontal flow unit \\ \end{tabular} & 35.0/11.0 & 35.0/11.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Indoor return air temperature standard rating conditions [11]. \begin{table}
\begin{tabular}{c} \(8\%\) RH to 28 \({}^{\circ}\)C(DPT) and 80\% RH \\ \end{tabular} & 28 & 3050 & N.A. & 5 to 45 & 8 to 80 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: ASHRAE 2015 Thermal Guidelines classes [10]. In contrast, AHRI 1361-2017 also offers the air intake temperatures in the condenser, as shown in Table 5. It must be noted that:  
1. All ratings are at standard atmospheric pressure. 2. For the NetSCOP calculation, add allowance for cooling tower fan(s) and heat rejection loop, water pump power input in kW to the unit total input in kW = 5% of the unit net sensible capacity. 3. For the NetSCOP calculation, add allowance for dry cooler fan(s) and heat rejection loop glycol pump power input in kW to the unit total input in kW = 7.5% of the unit net sensible capacity. 4. For the NetSCOP calculation, add allowance for chilled water pump power input in kW to unit total input in kW (See Equation (1)).