This group of building descriptors applies to all cooling systems.
Cooling Source 


Applicability 
All systems 
Definition 
The source of cooling for the system. The choices are:

Units 
List (see above) 
Input Restrictions 
As designed 
Baseline Rules 
The baseline building cooling source is direct expansion for systems 16 and chilled water for systems 78 and 1113. Systems 9 and 10 have no cooling capability. See Table 3.72. 
Total Cooling Capacity 


Applicability 
All cooling systems 

Definition 
The total cooling capacity (both sensible and latent) of a cooling coil or packaged DX system at AHRI test conditions. The building descriptors defined in this chapter assume that the fan is modeled separately, including any heat it adds to the air stream. The cooling capacity specified by this building descriptor should not consider the heat of the fan. 

Units 
kBtu/h 

Input Restrictions 
As designed. Fan energy shall be modeled separately from cooling, unless the fan cycles, so for packaged equipment that has the fan motor in the air stream the Total Cooling Capacity shall be adjusted for the heat generated by the fan using the following procedure . (Equation 3.7.5.11) $$Q_{Net} = Q_{Rated}  Q_{Fan}$$ (Equation 3.7.5.12) $$Q_{Fan}=\frac{Q_{Rated}}{COP_{cooling}}\frac{Q_{Rated}}{COP_{nfcooling}}$$
where


Baseline Rules 
The total cooling capacity of the baseline building system is oversized by 15%. Sizing calculations shall be based on 1% drybulb and 1% wetbulb design conditions. 
Sensible Cooling Capacity 


Applicability 
All cooling systems 

Definition 
The sensible heat cooling capacity of the coil or packaged equipment at ARI conditions. The building descriptors defined in this chapter assume that the fan is modeled separately, including any heat it adds to the air stream. The cooling capacity specified by this building descriptor should not consider the heat of the fan. 

Units 
kBtu/h 

Input Restrictions 
As designed. For packaged equipment that has the fan motor located in the air stream such that it adds heat to the cooled air, the software shall adjust the sensible cooling capacity as follows: (Equation 3.7.5.13) $$Q_{s.adj} = Q_{s,rated} + BHP_{supply} \times 2.545$$ ==Where


Baseline Rules 
The sensible cooling capacity of the baseline building is oversized by 15%. Sizing calculations shall be based on 1% drybulb and 1% wetbulb design conditions. 
Cooling Capacity Adjustment Curves 


Applicability 
All cooling systems 

Definition 
A curve that represents the available total cooling capacity as a function of cooling coil and/or condenser conditions. The common form of these curves is given as follows: (Equation 3.7.5.14) $$Q_{t,available}=CAP\_FT \times Q_{t,adj}$$ For air cooled direct expansion (Equation 3.7.5.15) $$CAP\_FT=a + b \cdot t_{wb}+ c \cdot t_{wb}^{2}+ d \cdot t_{odb}+ d \cdot t_{odb}^{2}+f\cdot t_{wb}\cdot t_{odb}$$ For water cooled direct expansion (Equation 3.7.5.16) $$CAP\_FT=a + b \cdot t_{wb}+ c \cdot t_{wb}^{2}+ d \cdot t_{wt}+ d \cdot t_{wt}^{2}+f\cdot t_{wb}\cdot t_{wt}$$ For chilled water coils (Equation 3.7.5.17) $$CAP\_FT=a + b \cdot t_{wb}+ c \cdot t_{wb}^{2}+ d \cdot t_{db}+ d \cdot t_{db}^{2}+f\cdot t_{wb}\cdot t_{db}$$ Where
Note: if an aircooled unit employs an evaporative condenser, t_{odb} is the effective drybulb temperature of the air leaving the evaporative cooling unit. 

Units 
Data structure 

Input Restrictions 
As designed. The equations and coefficients given above are the default. 

Baseline Rules 
The default curves shall be used for the baseline HVAC system. 
Coil Bypass Factor 


Applicability 
All cooling systems 

Definition 
The ratio of air that bypasses the cooling coil at design conditions to the total system airflow. 

Units 
Ratio 

Input Restrictions 
The rated building shall use the factors given below. Table 3.7.5.11: Default Coil Bypass Factors


Baseline Rules 
Same as the rated building 
Coil Bypass Factor Adjustment Curves 


Applicability 
All DX cooling systems (optional input) 

Definition 
Adjustments for the amount of coil bypass due to the following factors:


Units 
Data structure 

Input Restrictions 
Where applicable, the following default values shall be used for the coil bypass factor adjustment curve: (Equation 3.7.5.18) $$CBF_{adj}=CBF_{Rated} \times COIL\_BF\_FFLOW \times COIL\_BF\_FT \times COIL\_BF\_FPLR$$ (Equation 3.7.5.19) $$COIL\_BF\_FFLOW = a + b\cdot CFMR + c \cdot CFMR^{2} + d \cdot CFMR^{3}$$ (Equation 3.7.5.110) $$COIL\_BF\_FT = a + b\cdot T_{wb} + c \cdot T_{wb}^{2} + b\cdot T_{db} + c \cdot T_{db}^{2} +f\cdot T_{wb} \cdot T_{db}$$ Equation 3.7.5.111) $$COIL\_BF\_FPLR = a + b\cdot PLR$$ Where


Baseline Rules 
The above default values shall be used when applicable. 