2.5 Air Handling Unit Group

2.5 Primary Energy Consumption of an Air Handling Unit Group

2.5.1 Daily Integrated Room Load Handled by an Air Handling Unit Group

The daily integrated room load handled by each air handling unit group is calculated by totalizing the room loads of the rooms where the air handling unit group handles the load.

Table 47. Input

Variable Name	Description	Unit	Reference
\(A_{room,i,r}\)	Area of room r belonging to air handling unit group	m2	Form 2-1: (1) Floor Area
\(EquipmentName_{AC,ahu,room,i,r}\)	Air handling unit group name for room load handling of room r belonging to air handling unit group	-	Form 2-1: (3) Room Load Handling
\(Q_{AC,room,c,r,d}\)	Daily integrated room load (cooling) of room r on date \(d\)	Wh/(m2・d)	2.4.4
\(Q_{AC,room,h,r,d}\)	Daily integrated room load (heating) of room r on date \(d\)	Wh/(m2・d)	2.4.4

Table 48. Output

Variable Name	Description	Unit	References
\(OnlyOALoad_{AC,ahu,i}\)	Whether or not the air handling unit group i handles only outside air load	Boolean value	2.5.2
\(Q_{AC,ahu,room,c,i,d}\)	Daily integrated room load (cooling) of the air handling unit group i on date \(d\)	MJ/d	2.5.2, 2.5.5, 2.5.4
\(Q_{AC,ahu,room,h,i,d}\)	Daily integrated room load (heating) on date \(d\) for air handling unit group	MJ/d	2.5.2, 2.5.5

Whether or not the air handling unit group i handles only outside air load \(OnlyOALoad_{AC,ahu,i}\) is False if the name of the air handling unit group i matches at least one of the names of the air handling unit group for handling room load of room r belonging to the air handling unit group i \(EquipmentName_{AC,ahu,room,i,r}\) , and True otherwise.

\[ OnlyOALoad_{AC,ahu,i} = \begin{cases} {\mathrm{False}} & ,(EquipmentName_{AC,ahu,room,i,r} = \mbox{name of air handling unit group i}) \\ {\mathrm{True}} & ,(\mbox{otherwise}) \end{cases} \]

The daily integrated room load (cooling) \(Q_{AC,ahu,room,c,i,d}\) and daily integrated room load (heating) \(Q_{AC,ahu,room,h,i,d}\) of the air handling unit group i on date \(d\) are calculated by the following formula. For the air handling unit group that handles only outside air load, the daily integrated room load should be set to 0, and only the outside air load should be integrated as described below.

a) If only the outside air load is processed ( \(OnlyOALoad_{AC,ahu,i} = {\mathrm{True}}\) ),

\[ Q_{AC,ahu,room,c,i,d} = 0 \]

\[ Q_{AC,ahu,room,h,i,d} = 0 \]

b) Otherwise,

\[ Q_{AC,ahu,room,c,i,d} = \sum_{r=1} \left( Q_{AC,room,c,r,d} \times A_{room,i,r} \right) \times 3600 \times 10^{-6} \]

\[ Q_{AC,ahu,room,h,i,d} = \sum_{r=1} \left( Q_{AC,room,h,r,d} \times A_{room,i,r} \right) \times 3600 \times 10^{-6} \]

2.5.2 Operating Hours of an Air conditioner Group

The operating hours of an air handling unit group are calculated as the total value of the used hours of the rooms in which the relevant air handling unit group performs air conditioning.

Table 49. Input

Variable Name	Description	Unit	Reference
\(O_{AC,room,r,d,t}\)	Presence or Absence of air conditioning operation of room r at date \(d\), time \(t\)	Boolean value	2.3.3
\(Q_{AC,ahu,room,c,i,d}\)	Daily integrated room load (cooling) of the air handling unit group i on date \(d\)	MJ/d	2.5.1
\(Q_{AC,ahu,room,h,i,d}\)	Daily integrated room load (heating) on date \(d\) for air handling unit group	MJ/d	2.5.1
\(OnlyOALoad_{AC,ahu,i}\)	Whether or not the air handling unit group i handles only outside air load	Boolean value	2.5.1

Table 50. Output

Variable Name	Description	Unit	References
\(T_{AC,ahu,i,d}\)	Operating hours of the air handling unit group i on date \(d\)	h/d	2.5.3, 2.5.5, 2.5.10
\(T_{AC,ahu,aex,i,d}\)	Operating hours of the total heat exchangers of the air handling unit group i on date \(d\)	h/d	2.5.12
\(T_{AC,ahu,c,i,d}\)	Cooling operation hours of the air handling unit group i on date \(d\)	h/d	2.5.4, 2.5.10, 2.5.6, 2.5.12
\(T_{AC,ahu,h,i,d}\)	Heating operation hours of the air handling unit group i on date \(d\)	h/d	2.5.10, 2.5.6, 2.5.12
\(O_{AC,ahu,i,d,t}\)	Operation status of the air handling unit group i at date \(d\), time \(t\)	Boolean value	2.6.2

The operating hours of the air handling unit group i on date \(d\) \(T_{AC,ahu,i,d}\) is calculated by totalizing the operating status of the air handling unit group i at each time on a daily basis, assuming that the air handling unit group i is operating if any one of the rooms r that are air-conditioned by the air conditioner j belonging to the air handling unit group i, is performing air conditioning at each time.

First, calculate the operating status of the air handling unit group i at date \(d\), time \(t\)\(O_{AC,ahu,i,d,t}\). For a room air conditioned by the air handling unit group i, if \(O_{AC,room,r,d,t}\) is True in one room, then \(O_{AC,ahu,i,d,t}\) is True; if \(O_{AC,room,i,d,t}\) is False in all rooms, then \(O_{AC,ahu ,i,d,t}\) is False.

The operating hours of the air handling unit group i on date \(d\) \(T_{AC,ahu,i,d}\) is calculated by counting the number of hours for which \(O_{AC,ahu,i,d,t}\) is True on each day.

Next, calculate the cooling and heating operation hours of each air handling unit group. The daily integrated room load for each air handling unit group was calculated as above, but both the absolute values of the cooling room load and heating room load can be greater than zero on the same day. This means that both loads occur in a day, for example, the heating room load occurs in the morning, but the cooling room load occurs in the afternoon. However, since this calculation method calculates the daily integrated room load, it is not known at what time of the day the cooling room load and heating room load occurred. Therefore, it was decided to determine the cooling and heating operation hours by proportionally dividing the daily integrated air conditioning operation hours by the ratio of the absolute values of the cooling room load and the heating room load. However, the terms "cooling" and "heating" here indicate that the room load generated is the cooling (or heating) load. And the air conditioning load that is the room load plus the outside air load is not necessarily the cooling (or heating) load. In addition, as discussed in detail below, when the heat source system does not have a simultaneous cooling and heating supply function (i.e., it has a switching function between cooling and heating operations depending on the season), the heating load in the cooling and intermediate seasons and the cooling load in the heating season are assumed to be ignored without being processed (this is called the "unprocessed load").

The cooling operation hours \(T_{AC,ahu,c,i,d}\) and heating operation hours \(T_{AC,ahu,h,i,d}\) of the air handling unit group i are obtained by the following formula.

a) If only the outside air load is processed ( \(OnlyOALoad_{AC,ahu,i} = {\mathrm{True}}\) ) For the air handling unit groups that process only outside air load, the room load to be processed is 0 for both cooling and heating, so the following formula is used for convenience.

\[ T_{AC,ahu,c,i,d} = T_{AC,ahu,i,d} \]

\[ T_{AC,ahu,h,i,d} = 0 \]

b) In other cases,

b-1) If there is no operating hours for the air handling unit group i ( \(T_{AC,ahu,i,d}=0\)),

\[ T_{AC,ahu,c,i,d} = 0 \]

\[ T_{AC,ahu,h,i,d} = 0 \]

b-2) In other cases,

b-2-1) If the absolute value of the room load (heating) is greater than the absolute value of room load (cooling) ( \(| Q_{AC,ahu,room,c,i,d}| < |Q_{AC,ahu,room,h,i,d}|\) ),

\[ T_{AC,ahu,c,i,d} = ceil( T_{AC,ahu,i,d} \times \frac{|Q_{AC,ahu,room,c,i,d}|}{|Q_{AC,ahu,room,c,i,d}|+|Q_{AC,ahu,room,h,i,d}|} ) \]

\[ T_{AC,ahu,h,i,d} = T_{AC,ahu,i,d} - T_{AC,ahu,c,i,d} \]

b-2-2) Otherwise,

\[ T_{AC,ahu,h,i,d} = ceil( T_{AC,ahu,i,d} \times \frac{|Q_{AC,ahu,room,h,i,d}|}{|Q_{AC,ahu,room,c,i,d}|+|Q_{AC,ahu,room,h,i,d}|} )\]

\[ T_{AC,ahu,c,i,d} = T_{AC,ahu,i,d} - T_{AC,ahu,h,i,d} \]

In the formula, "ceil" is a function that means to round up the decimal point and obtain an integer value.

Assume that the operating hours of the total heat exchanger \(T_{AC,ahu,aex,i,d}\) is the same as that of the air handling unit group i.

\[ T_{AC,ahu,aex,i,d} = T_{AC,ahu,i,d} \]

2.5.3 Outside Air Load

Calculate the outside air load handled by an air handling unit group.

Table 51. Input

Variable Name	Description	Unit	Reference
\(A_{room,i,r}\)	Area of room r belonging to air handling unit group	m2	Form 2-1: (1) Floor Area
\(EquipmentName_{AC,ahu,oa,i,r}\)	Name of the air handling unit group for outside air load treatment of room r belonging to air handling unit group	-	Form 2-1: (4) Outside Air Load Handling
\(EquipmentName_{AC,ahu,i}\)	Name of the air handling unit group	-	Form 2-7: (1) Name of the Air Handling Unit Group
\(N_{AC,ahu,i,j}\)	Number of fans j belonging to the air handling unit group	Number of devices	Form 2-7: (2) Number of Devices
\(TotalHeatExchanger_{AC,ahu,i,j}\)	Presence or Absence of total heat exchangers of fan j belonging to the air handling unit group	Present/Absent	Form 2-7: (15) Presence or Absence of a Total Heat Exchanger
\(V_{AC,ahu,aex,i,j}\)	Design airflow rate of the total heat exchangers of fan j belonging to air handling unit group	m3/ (h・device)	Form 2-7: (16) Design Airflow Volume of a Total Heat Exchanger
\(\eta_{ahu,aex,i,j}\)	The total heat exchange efficiency of total heat exchangers of fan j belonging to the air handling unit group	%	Form 2-7: (16) Total Heat Exchange Efficiency
\(AutoChangeCtrl_{ahu,aex,i,j}\)	Presence or Absence of automatic ventilation switching function of total heat exchangers of fan j belonging to air handling unit group	Present/Absent	Form 2-7: (18) Presence or Absence of Automatic Ventilation Switching Function
\(V_{AC,room,oa,i,r}\)	Fresh outside air volume into room r belonging to the air handling unit group	m3/(h・m2)	2.3.5
\(T_{AC,ahu,i,d}\)	Operating hours of the air handling unit group i on date \(d\)	h/d	2.5.2
\(H_{AC,oa,d,alltime}\)	Outside air enthalpy on date \(d\).	kJ/kg	2.2.4
\(H_{AC,oa,d,daytime}\)	Outside air enthalpy during daytime on date \(d\)	kJ/kg	2.2.4
\(H_{AC,oa,d,nighttime}\)	Outside air enthalpy during nighttime on date \(d\)	kJ/kg	2.2.4
\(H_{AC,room,d}\)	Inside air enthalpy during air conditioning on date \(d\)	kJ/kg	2.3.2
\(Season_{d}\)	Cooling/heating season (cooling, intermediate, or heating seasons) on date \(d\)	-	2.2.2
\(OperatingTime_{AC,room,r}\)	Operating time zone of room r air conditioners (all day, daytime, nighttime)	-	2.3.3

Table 52. Output

Variable Name	Description	Unit	References
\(V_{AC,ahu,oa,i}\)	Fresh outside air volume by the air handling unit group	kg/s	2.5.4
\(\Delta H_{AC,oa,d}\)	Enthalpy difference between outside and inside air on date \(d\)	kJ/kg	2.5.4
\(q_{AC,ahu,oa,i,d}\)	Outside air load of the air handling unit group i on date \(d\)	kW	2.5.5

First, calculate the outside air volume by air handling unit group i \(V_{AC,ahu,oa,i}\). The integrated value of the outside air volume by air handling unit group i to all rooms to be air conditioned \(V_{AC,room,oa,i,r}\) should be the outside air volume by air handling unit group i \(V_{AC,ahu,oa,i}\).

\[ V_{AC,ahu,oa,i} = \sum_{r} \left( V_{AC,room,oa,i,r} \times A_{room,i,r} \right) \times \frac{1.293}{3600} \]

Next, calculate the supply airflow rate \(V_{AC,ahu,aex,i}\) [kg/s] of the total heat exchangers belonging to the air handling unit group i.

\[ V_{AC,ahu,aex,i} = \sum_{j} \left( V_{AC,ahu,aex,i,j} \times N_{AC,ahu,i,j} \right) \times \frac{1.293}{3600} \]

The daily average outside air enthalpy on date \(d\) is obtained by the following formula. If an air handling unit group runs all day, the daily average of outside air enthalpy is used; when it runs at night over several days, the night-time average of outside air enthalpy is used; and when it runs only during the day, the daytime average is used.

\[ H_{AC,oa,d} = \begin{cases} H_{AC,oa,d,alltime} & ,(\mbox{all-day operation}) \\ H_{AC,oa,d,daytime} & ,(\mbox{daytime operation}) \\ H_{AC,oa,d,nighttime} & ,(\mbox{night-time operation}) \end{cases} \]

The operating time zone of a air handling unit group depends on the used time zone of the rooms to which they are connected. If the use time zones of all connected rooms are the same, the operating time zone of the air handling unit group is equal to it. However, if the use time zones differ depending on the connected room, it is considered as an "all-day operation" without depending on the combination of them.

The enthalpy difference between inside and outside is calculated by the following formula.

\[ \Delta H_{AC,oa,d} = H_{AC,oa,d} - H_{AC,room,d} \]

\(OnlyRoomLoad_{AC,ahu,i}\), which indicates whether the air handling unit group i handles only room load, is False if the name of the air handling unit group i matches at least one of the names of the air handling unit groups for handling outside air load of room r belonging to the air handling unit group i \(EquipmentName_{AC,ahu,oa,i,r}\). Otherwise, it is assumed to be True.

\[ OnlyRoomLoad_{AC,ahu,i} = \begin{cases} {\mathrm{False}} & ,(EquipmentName_{AC,ahu,oa,i,r} = EquipmentName_{AC,ahu,i}) \\ {\mathrm{True}} & ,(\mbox{otherwise}) \end{cases} \]

\(AutoChangeCtrl_{ahu,aex,i}\), which indicates whether the automatic ventilation switching function is enabled for the total heat exchangers of the air handling unit group i, is "Enabled" if the automatic ventilation switching function is enabled in at least one of the total heat exchangers of fan j belonging to the air handling unit group i. Otherwise, it is assumed to be "Disabled".

a) If there is one or more total heat exchangers (\(AutoChangeCtrl_{ahu,aex,i,j} = \mbox{Enabled}\)) for which the automatic ventilation switching function is enabled,

\[ AutoChangeCtrl_{ahu,aex,i} = \mbox{Enabled} \]

b) In other cases,

\[ AutoChangeCtrl_{ahu,aex,i} = \mbox{Disabled} \]

The outside air load of the air handling unit group i on date \(d\) \(q_{AC,ahu,oa,i,d}\) is calculated by the following formula. When calculating the outside air load, the load reduction effect is expected when each air handling unit group includes a total heat exchanger, but the calculation method differs depending on whether the total heat exchanger is equipped with an automatic ventilation switching function.

a) If only the inside load is handled, or if there is no operating hour for the air handling unit group i, ( \(OnlyRoomLoad_{AC,ahu,i} = {\mathrm{True}} \lor T_{AC,ahu,i,d} = 0\) )

\[ q_{AC,ahu,oa,i,d} = 0 \]

b) In other cases,

b-1) For the heating season ( \(Season_{d} = \mbox{heating season}\)),

b-1-1) If the automatic ventilation switching function of the total heat exchangers is enabled and the difference value between inside and outside enthalpies is positive, ( \(AutoChangeCtrl_{ahu,aex,i} = \mbox{Enabled} \land \Delta H_{AC,oa,d}>0\))

\[ q_{AC,ahu,oa,i,d} = \Delta H_{AC,oa,d} \times V_{AC,ahu,oa,i} \]

b-1-2) In other cases,

\[ q_{AC,ahu,oa,i,d} = \Delta H_{AC,oa,d} \times \max⁡(0,V_{AC,ahu,oa,i} - V'_{AC,ahu,aex,i} \times \eta'_{ahu,aex,i}) \]

b-2) In other cases,

b-2-1) If the automatic ventilation switching function of the total heat exchangers is enabled and the difference value between inside and outside enthalpies is not positive, (\(AutoChangeCtrl_{ahu,aex,i} = \mbox{Enabled} \land ΔH_{AC,oa,d} \leqq 0\))

\[ q_{AC,ahu,oa,i,d} = \Delta H_{AC,oa,d} \times V_{AC,ahu,oa,i} \]

b-2-2) In other cases,

\[ q_{AC,ahu,oa,i,d} = \Delta H_{AC,oa,d} \times \max⁡(0,V_{AC,ahu,oa,i} - V'_{AC,ahu,aex,i} \times \eta'_{ahu,aex,i}) \]

\(V'_{AC,ahu,aex,i}\) in the formula is the supply airflow rate of total heat exchangers belonging to the air handling unit group i, capped by the outside air volume, and is calculated by the following formula.

\[ V'_{AC,ahu,aex,i} = \min⁡(V_{AC,ahu,aex,i},V_{AC,ahu,oa,i}) \]

The \(\eta'_{ahu,aex,i}\) [-] in the formula is the total heat exchange efficiency of total heat exchangers belonging to the air handling unit group i corrected by considering the actual operating performance, and is calculated by the following formula \(C_{tol}\) is a coefficient related to the indicated value, \(C_{eff}\) is a coefficient related to the effective ventilation rate, and \(C_{bal}\) is a coefficient related to the balance between supply air volume and exhaust air volume.

\[ \eta'_{ahu,aex,i} = \begin{cases} \frac{\eta_{ahu,aex,i}}{100} \times C_{tol} \times C_{eff} \times C_{bal} & ,(\eta_{ahu,aex,i} > 0) \\ 0 & ,(\eta_{ahu,aex,i} = 0) \end{cases} \]

\[ C_{tol} = 0.95 \]

\[ C_{eff} = 1 - \left(\frac{1}{0.85} - 1\right) \times \frac{1 - \frac{\eta_{ahu,aex,i}}{100}} {\frac{\eta_{ahu,aex,i}}{100}} \]

\[ C_{bal} = 0.67 \]

\(\eta_{ahu,aex,i}\) [%] in the formula is the total heat exchange efficiency of total heat exchangers belonging to the air handling unit group i before correction, and you should adopt the worst total heat exchange efficiency among the total heat exchangers of fan j belonging to air handling unit group i.

a) If there is more than one fan with a total heat exchanger ( \(TotalHeatExchanger_{AC,ahu,i,j} = \mbox{Yes}\)),

\[ \eta_{ahu,aex,i} = \min \{ \eta_{ahu,aex,i,j} \mid TotalHeatExchanger_{AC,ahu,i,j} = \mbox{Yes} \} \]

b) In other cases,

\[ \eta_{ahu,aex,i} = 0 \]

\(C_{tol}\) is a coefficient considering the allowable range of indicated value specified in JIS B 8628:2003, \(C_{eff}\) is a coefficient considering the allowable range of effective ventilation rate in the same standard, and \(C_{bal}\) is the reduction ratio of the total heat exchange efficiency when the ratio of actual supply air volume and exhaust air volume is assumed to be 2:1 while considering the description (the use of a total heat exchanger should be considered only in such cases as where the exhaust air volume can be maintained at approximately 40% of the outside air volume) in the Building Equipment Design Standards (supervised by the Building Equipment and Environment Division, Government Buildings Department, Minister’s Secretariat, Ministry of Land, Infrastructure, Transport and Tourism). In practice, it is possible to obtain better total heat exchange efficiency by using the effective ventilation rate, and total heat exchange efficiency under the design conditions of the adopted model. However, at present, there are issues on how to specify these in the design documents and how to adjust and check the building equipment after construction and completion. Therefore, the calculation is based on a coefficient that assumes the safe side (lower efficiency) as described above.

2.5.4 Load Reduction by Outside Air Cooling Control

Calculate the load reduction by outside air cooling control of the air handling unit group i on date \(d\).

Table 53. Input

Variable Name	Description	Unit	Reference
\(N_{AC,ahu,i,j}\)	Number of air conditioners j belonging to the air handling unit group	Number of devices	Form 2-7: (2) Number of Devices
\(V_{AC,ahu,oacool,i,j,max,unit}\)	Design maximum outside airflow rate per air conditioner j belonging to the air handling unit group	m3/ (h・device)	Form 2-7: (6) Design Maximum Outside Airflow Volume
\(OACoolingCtrl_{AC,ahu,i}\)	Presence or Absence of outside air cooling control	Present/Absent	Form 2-7: (14) Presence or Absence of Outside Air Cooling Control
\(T_{AC,ahu,c,i,d}\)	Air conditioning operation hours of (cooling) air handling unit group i on date \(d\)	h/d	2.5.2
\(Q_{AC,ahu,room,c,i,d}\)	Daily integrated room load (cooling) of the air handling unit group i on date \(d\)	MJ/d	2.5.1
\(V_{AC,ahu,oa,i}\)	Fresh outside air volume by the air handling unit group	kg/s	2.5.3
\(ΔH_{AC,oa,d}\)	Enthalpy difference between outside and inside air on date \(d\)	kJ/kg	2.5.3

Table 54. Output

Variable Name	Description	Unit	References
\(Q_{AC,ahu,oacool,i,d}\)	Load reduction by outside air cooling control of the air handling unit group i on date \(d\)	MJ/d	2.6.1

First, calculate the design maximum outside air volume for air handling unit group i \(V_{AC,ahu,oacool,max,i}\) [kg/s]. If Form 2-7: (6) Design maximum Outside Airflow Volume is blank, \(V_{AC,ahu,oacool,max,i}\) is assumed to be 0.

\[ V_{AC,ahu,oacool,max,i} = \sum \left( V_{AC,ahu,oacool,max,i,j,unit} \times N_{AC,ahu,i,j} \right) \times \frac{1.293}{3600} \]

Next, calculate the airflow rate during outside air cooling \(V_{AC,ahu,oacool,i,d}\). The supply airflow rate during outside air cooling should not exceed the design maximum outside airflow rate \(V_{AC,ahu,oacool,max,i}\).

a) Outside air cooling control is enabled and the cooling operation hours is a positive number ( \(OACoolingCtrl_{AC,ahu,i} = \mbox{Yes} \land T_{AC,ahu,c,i,d}>0\) ).

\[ V_{AC,ahu,oacool,i,d} = \min\left( V_{AC,ahu,oacool,i,max},\ \max(V_{AC,ahu,oa,i},\, V) \right) - V_{AC,ahu,oa,i} \]

\[ V = \frac{ Q_{AC,ahu,room,c,i,d} \times 10^{3} } { 3600 \times ( - \Delta H_{AC,oa,d} ) \times T_{AC,ahu,c,i,d} } \]

b) outside air cooling control is disabled or there is no cooling operation hour ( \(OACoolingCtrl_{AC,ahu,i} = \mbox{none} \lor T_{AC,ahu,c,i,d}=0\) ).

\[ V_{AC,ahu,oacool,i,d} = 0 \]

The load reduction by outside air cooling control \(Q_{AC,ahu,oacool,i,d}\) is calculated by the following formula.

\[ Q_{AC,ahu,oacool,i,d} = V_{AC,ahu,oacool,i,d} \times ( - \Delta H_{AC,oa,d} ) \times T_{AC,ahu,c,i,d} \times \frac{ 10^{-3} }{ 3600 } \]

2.5.5 Daily Integrated Air Conditioning Load

The daily integrated air conditioning load is calculated by adding the outside air load to the room load of each air handling unit group. In this calculation, consider the effect of introducing the "Control to Stop Outside Air Introduction During Preheating".

Table 55. Input

Variable Name	Description	Unit	Reference
\(OACutCtrl_{AC,ahu,i}\)	Presence or Absence of the "Control to Stop Outside Air Introduction During Preheating"	Present/Absent	Form 2-7 (13) : Presence or Absence of the "Stop Outside Air Introduction During Preheating" process
\(SimultenousCtrl_{AC,ref,j}\)	Presence or Absence of providing simultaneous cooling and heating by the heat source group j, to which air handling unit group i belongs	Present/Absent	Form 2-5 (2): Presence or Absence of Simultaneous Supply Function of Heating and Cooling
\(T_{AC,ahu,i,d}\)	Operating hours of the air handling unit group i on date \(d\)	h/d	2.5.2
\(T_{AC,ahu,c,i,d}\)	Cooling operation hours of the air handling unit group i on date \(d\)	h/d	2.5.2
\(T_{AC,ahu,h,i,d}\)	Heating operation hours of the air handling unit group i on date \(d\)	h/d	2.5.2
\(q_{AC,ahu,oa,i,d}\)	Outside air load of the air handling unit group i on date \(d\)	kW	2.5.3
\(Q_{AC,ahu,room,h,c,d}\)	Daily integrated room load (cooling) of the air handling unit group i on date \(d\)	MJ/d	2.5.1
\(Q_{AC,ahu,room,h,i,d}\)	Daily integrated room load (heating) to air handling unit group i on date \(d\)	MJ/d	2.5.1
\(Season_{d}\)	Cooling/heating season (cooling, intermediate, or heating seasons) on date \(d\)	-	2.2.2
\(OnlyOALoad_{AC,ahu,i}\)	Whether or not the air handling unit group i handles only outside air load	Boolean value	2.5.1

Table 56. Output

Variable Name	Description	Unit	References
\(Q_{AC,ahu,c,i,d}\)	Daily integrated air conditioning load (cooling) of the air handling unit group i on date \(d\)	MJ/d	2.6.1, 2.5.6
\(Q_{AC,ahu,h,i,d}\)	Daily integrated air conditioning load (heating) of the air handling unit group i on date \(d\)	MJ/d	2.6.1, 2.5.6

Calculate the daily integrated air conditioning load (cooling) using the following procedure.

• a) If only the outside air load is handled (\(OnlyOALoad_{AC,ahu,i} = {\mathrm{True}}\)),

  • a-1) If there is no control to stop outside air introduction during preheating (\(OACutCtrl_{AC,ahu,i} = \mbox{no}\)),

    \[ Q_{ahu,c} = q_{AC,ahu,oa,i,d} \times T_{AC,ahu,i,d} \times 3600 \times 10^{-3} \]

  • a-2) If there is a control to stop introduction of outside air during preheating (\(OACutCtrl_{AC,ahu,i} = \mbox{Present}\)),

    • a-2-1) If the operating hours of the air handling unit group i is greater than 1 (\(T_{AC,ahu,i,d} > 1\)),

      \[ Q_{ahu,c} = q_{AC,ahu,oa,i,d} \times (T_{AC,ahu,i,d} - 1) \times 3600 \times 10^{-3} \]

    • a-2-2) In other cases,

      \[ Q_{ahu,c} = q_{AC,ahu,oa,i,d} \times T_{AC,ahu,i,d} \times 3600 \times 10^{-3} \]

• b) In other cases,

  • b-1) If the cooling operation hours of the air handling unit group i is a positive number (\(T_{AC,ahu,c,i,d}>0\)),

    • b-1-1) If there is a control to stop introduction of outside air during preheating, and the cooling operation hours of the air handling unit group i is greater than 1, and the cooling operation hours of the air handling unit group i is greater than heating operation hours (\(OACutCtrl_{AC,ahu,i} = \mbox{Present} \land T_{AC,ahu,c,i,d} > 1 \land T_{AC,ahu,c,i,d} \geqq T_{AC,ahu,h,i,d}\)),

      \[ Q_{ahu,c} = Q_{AC,ahu,room,c,i,d} + q_{AC,ahu,oa,i,d} \times (T_{AC,ahu,c,i,d} - 1) \times 3600 \times 10^{-3} \]

    • b-1-2) In other cases,

      \[ Q_{ahu,c} = Q_{AC,ahu,room,c,i,d} + q_{AC,ahu,oa,i,d} \times T_{AC,ahu,c,i,d} \times 3600 \times 10^{-3} \]

  • b-2) In other cases,

    \[ Q_{ahu,c} = 0 \]

Calculate the daily integrated air conditioning load (heating) using the following procedure. However, if only the outside air load is handled, the daily integrated air conditioning load (heating) is 0 because the outside air load is handled as the cooling load for processing purposes.

• a) If only the outside air load is handled (\(OnlyOALoad_{AC,ahu,i} = {\mathrm{True}}\)),

  \[ Q_{ahu,h} = 0 \]

• b) In other cases,

  • b-1) If the heating operation hours of the air handling unit group i is a positive number (\(T_{AC,ahu,c,i,d} > 0\)),

    • b-1-1) If there is a control to stop introduction of outside air during preheating, and the heating operation hours of the air handling unit group i is greater than 1, and the cooling operation hours of air handling unit group i is smaller than heating operation hours (\(OACutCtrl_{AC,ahu,i} = \mbox{Present} \land T_{AC,ahu,h,i,d} > 1 \land T_{AC,ahu,c,i,d} < T_{AC,ahu,h,i,d}\)),

      \[ Q_{ahu,h} = Q_{AC,ahu,room,h,i,d} + q_{AC,ahu,oa,i,d} \times (T_{AC,ahu,h,i,d} - 1) \times 3600 \times 10^{-3} \]

    • b-1-2) In other cases,

      \[ Q_{ahu,h} = Q_{AC,ahu,room,h,i,d} + q_{AC,ahu,oa,i,d} \times T_{AC,ahu,h,i,d} \times 3600 \times 10^{-3} \]

  • b-2) In other cases,

    \[ Q_{ahu,h} = 0 \]

2.5.6 Load Factor of an Air Handling Unit Group

The load factor of an air handling unit group is determined by the air conditioning load (coil load) handled by relevant air handling unit group.

Table 57. Input

Variable Name	Description	Unit	Reference
\(N_{AC,ahu,i,j}\)	Number of air conditioners j belonging to the air handling unit group	Number of devices	Form 2-7: (2) Number of Devices
\(q_{AC,ahu,c,i,j,rated}\)	Rated cooling capacity of the air conditioner j belonging to the air handling unit group	kW/device	Form 2-7: (4) Rated Cooling Capacity
\(q_{AC,ahu,h,i,j,rated}\)	Rated heating capacity of air conditioner j belonging to air handling unit group	kW/device	Form 2-7: (5) Rated Heating Capacity
\(SimultenousCtrl_{AC,ref,i}\)	Presence or Absence of providing simultaneous cooling and heating by the heat source group i, to which air handling unit group i belongs	Present/Absent	Form 2-5 (2): Presence or Absence of Simultaneous Supply Function of Heating and Cooling
\(Q_{AC,ahu,c,i,d}\)	Daily integrated air conditioning load (cooling) of the air handling unit group i on date \(d\)	MJ/d	2.5.5
\(Q_{AC,ahu,h,i,d}\)	Daily integrated air conditioning load (heating) of the air handling unit group i on date \(d\)	MJ/d	2.5.5
\(T_{AC,ahu,c,i,d}\)	Cooling operation hours of the air handling unit group i on date \(d\)	h/d	2.5.2
\(T_{AC,ahu,h,i,d}\)	Heating operation hours of the air handling unit group i on date \(d\)	h/d	2.5.2
\(Season_{d}\)	Cooling/heating season (cooling, intermediate, or heating seasons) on date \(d\)	-	2.2.2

Table 58. Output

Variable Name	Description	Unit	References
\(L_{AC,ahu,c,i,d}\)	Load factor during cooling operation of the air handling unit group i on date \(d\)	-	2.5.10, 2.5.7, 2.5.12
\(L_{AC,ahu,h,i,d}\)	Load factor during heating operation of the air handling unit group i on date \(d\)	-	2.5.10, 2.5.7, 2.5.12

First, calculate the load factor in the cooling season of the air handling unit group i on date \(d\) \(L_{AC,ahu,mix,c,i,d}\) and the load factor in the heating season of the air handling unit group i on date \(d\) \(L_{AC,ahu,mix,h,i,d}\). In this calculation method, the daily average load factor is calculated using the daily integrated load, and then, the energy consumption is calculated assuming that the equipment operates at this constant load factor throughout a day.

\[ q_{AC,ahu,c,i,rated} = \sum_{j} \left( q_{AC,ahu,c,i,j,rated} \times N_{AC,ahu,i,j} \right) \]

\[ q_{AC,ahu,h,i,rated} = \sum_{j} \left( q_{AC,ahu,h,i,j,rated} \times N_{AC,ahu,i,j} \right) \]

\[ L_{AC,ahu,mix,c,i,d} = \begin{cases} F(0) & ,(T_{AC,ahu,c,i,d} = 0) \\ F\left( \frac{Q_{AC,ahu,c,i,d} / T_{AC,ahu,c,i,d}} {q_{AC,ahu,c,i,rated} \times 3600 \times 10^{-3}} \right) & ,(T_{AC,ahu,c,i,d} > 0 \land Q_{AC,ahu,c,i,d} \ge 0) \\ F\left( \frac{Q_{AC,ahu,c,i,d} / T_{AC,ahu,c,i,d}} {q_{AC,ahu,h,i,rated} \times 3600 \times 10^{-3}} \right) & ,(T_{AC,ahu,c,i,d} > 0 \land Q_{AC,ahu,c,i,d} < 0) \end{cases} \]

\[ L_{AC,ahu,mix,h,i,d} = \begin{cases} F(0) & ,(T_{AC,ahu,h,i,d} = 0) \\ F\left( \frac{Q_{AC,ahu,h,i,d} / T_{AC,ahu,h,i,d}} {q_{AC,ahu,c,i,rated} \times 3600 \times 10^{-3}} \right) & ,(T_{AC,ahu,h,i,d} > 0 \land Q_{AC,ahu,h,i,d} \ge 0) \\ F\left( \frac{Q_{AC,ahu,h,i,d} / T_{AC,ahu,h,i,d}} {q_{AC,ahu,h,i,rated} \times 3600 \times 10^{-3}} \right) & ,(T_{AC,ahu,h,i,d} > 0 \land Q_{AC,ahu,h,i,d} < 0) \end{cases} \]

where the function F in the above formula is defined as follows. The function \(floor(x)\) finds the largest integer smaller than or equal to x for a real number x. The function \(ceil(x)\) finds the smallest integer greater than or equal to x for a real number x.

\[ F(L) = \begin{cases} \frac{\mathrm{floor}(L \times 10)}{10} + 0.05 & ,(L > 0) \\[0.7em] \frac{\mathrm{ceil}(L \times 10)}{10} - 0.05 & ,(L < 0) \\[0.7em] 0 & ,(L = 0) \end{cases} \]

The load factor during cooling operation and the load factor during heating operation of the air handling unit group i on date \(d\) are calculated by the following formula. In systems without simultaneous cooling and heating operation, the load factor is not set to 0 but to a small value ε (= 0.01) in order to calculate energy consumption assuming that the air conditioners are running at a low load rather than completely shutting down.

In addition, the presence or absence of simultaneous cooling/heating supply of heat source group i to which air handling unit group i belongs \(SimultenousCtrl_{AC,ref,i}\) obtains the value of Form 2-5: (2) Presence or Absence of Simultaneous Supply Function of Heating and Cooling by using the heat source group name (Form 2-7: (22) Cooling, (23) Heating) to which the air handling unit group i belongs as the search key.

a) If the operation of the air handling unit group i includes "simultaneous cooling and heating operation" ( \(SimultenousCtrl_{AC,ref,i} = \mbox{Yes}\) ),

\[ L_{AC,ahu,c,i,d} = L_{AC,ahu,mix,c,i,d} \]

\[ L_{AC,ahu,h,i,d} = L_{AC,ahu,mix,h,i,d} \]

b) If the operation of the air handling unit group i does not include "simultaneous cooling and heating operation" (\(SimultenousCtrl_{AC,ref,i} = \mbox{No}\)),

b-1) If the cooling/heating season \(Season_{d}\) is the "cooling season" or "intermediate season" （ \(Season_{d} = \mbox{cooling season} \lor Season_{d} = \mbox{intermediate season}\) ）

\[ L_{AC,ahu,c,i,d} = \max ⁡(L_{AC,ahu,mix,c,i,d},ε) \]

\[ L_{AC,ahu,h,i,d} = \max⁡ (L_{AC,ahu,mix,h,i,d},ε) \]

b-2) If the heating/cooling season \(Season_{d}\) is the "heating season" ( \(Season_{d} = \mbox{heating season}\)),

\[ L_{AC,ahu,c,i,d} = \min⁡(L_{AC,ahu,mix,c,i,d},-ε) \]

\[ L_{AC,ahu,h,i,d} = \min⁡(L_{AC,ahu,mix,h,i,d},-ε) \]

2.5.7 Coefficients Determined by Airflow Volume Control Method

Calculate the coefficients for calculating the energy saving effect due to airflow rate control.

Table 59. Input

Variable Name	Description	Unit	Reference
\(FanCtrlType_{AC,ahu,i,j}\)	Airflow rate control method of fan j belonging to the air handling unit group i (constant airflow rate control or rotational speed control)	-	Form 2-7: (11) Airflow Volume Control Method
\(L_{AC,ahu,i,j,min}\)	Minimum airflow rate ratio of fan j belonging to the air handling unit group	%	Form 2-7: (12) Minimum Airflow Volume Ratio at Variable Airflow Volume
\(L_{AC,ahu,c,i,d}\)	Load factor during cooling operation of the air handling unit group i on date \(d\)	-	2.5.6
\(L_{AC,ahu,h,i,d}\)	Load factor during heating operation of the air handling unit group i on date \(d\)	-	2.5.6

Table 60. Output

Variable Name	Description	Unit	References
\(f_{AC,ahu,c,i,j,d}\)	Coefficient determined by the airflow rate control method of fan j belonging to air handling unit group i (cooling)	-	2.5.9
\(f_{AC,ahu,h,i,j,d}\)	Coefficient determined by the airflow rate control method of fan j belonging to air handling unit group i (heating)	-	2.5.9

The coefficient determined by the airflow rate control method of fan j belonging to the air handling unit group i \(f_{AC,ahu,c,i,j,d}\) is obtained by the following formula.

If the minimum airflow rate ratio of fan j belonging to the air handling unit group i \(L_{AC,ahu,i,j,min}\) is blank in Form 2-7, it should be \(L_{AC,ahu,i,j,min} = 100\).

a) If \(|L_{AC,ahu,c,i,d}| > 1.0\),

\[ f_{AC,ahu,c,i,d} = 1.2 \]

b) If \(|L_{AC,ahu,c,i,d}| = 0\),

\[ f_{AC,ahu,c,i,d} = 0 \]

c) If \(|L_{AC,ahu,c,i,d}| < \frac{L_{AC,ahu,i,j,min}} {100}\),

\[ f_{AC,ahu,c,i,d} = F_{AC,ahu,i,j}\!\left( \frac{L_{AC,ahu,i,j,min}}{100} \right) \]

d) If \(\frac{L_{AC,ahu,i,j,min}} {100} ≤ |L_{AC,ahu,c,i,d}| ≤ 1.0\),

\[ f_{AC,ahu,c,i,d} = F_{AC,ahu,i,j}\!\left( |L_{AC,ahu,c,i,d}| \right) \]

The coefficient determined by the airflow rate control method of fan j belonging to the air handling unit group i is given by the following formula:

\[ f_{AC,ahu,h,i,j,d} \]

a) If \(|L_{AC,ahu,h,i,d}| > 1.0\),

\[ f_{AC,ahu,h,i,d} = 1.2 \]

b) If stem:[|L_{AC,ahu,h,i,d}| = 0,

\[ f_{AC,ahu,h,i,d} = 0 \]

c) If \(|L_{AC,ahu,h,i,d}| < \frac{L_{AC,ahu,i,j,min}} {100}\),

\[ f_{AC,ahu,h,i,d} = F_{AC,ahu,i,j}\!\left( \frac{L_{AC,ahu,i,j,min}}{100} \right) \]

d) If \(\frac{L_{AC,ahu,i,j,min}} {100} ≤ |L_{AC,ahu,h,i,d}| ≤ 1.0\),

\[ f_{AC,ahu,h,i,d} = F_{AC,ahu,i,j}\!\left( |L_{AC,ahu,h,i,d}| \right) \]

where the function \(F_{AC,ahu,i,j}(L)\) is a fourth-degree polynomial expressed as the following formula.

\[ F_{AC,ahu,i,j}(L) = a_{i,j} \times L^{4} + b_{i,j} \times L^{3} + c_{i,j} \times L^{2} + d_{i,j} \times L + e_{i,j} \]

The coefficient \(a_{i,j},b_{i.j},c_{i,j},d_{i,j},e_{i,j}\) is the coefficient representing energy consumption characteristic of each fan and is determined by the airflow rate control method \(FanCtrlType_{AC,ahu,i,j}\). If \(FanCtrlType_{AC,ahu,i,j}\) is not specified, it is assumed to be "constant airflow rate control".

Airflow rate control method \(FanCtrlType_{AC,ahu,i,j}\)	\(a_{i,j}\)	\(b_{i,j}\)	\(c_{i,j}\)	\(d_{i,j}\)	\(e_{i,j}\)
Constant airflow rate control	0	0	0	0	1
Rotational Speed Control	0	0	0	1	0

This energy consumption characteristic was defined based on the results of a field survey conducted by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) in its 2011 and 2012 Building Standard Improvement Promotion Project, Survey Item 36: "Empirical Evaluation of Energy Saving Effects through Optimal Control of Air Conditioning Systems, etc." The variable airflow rate control refers to the control in which the rotational speed of the fan automatically changes according to the room temperature, etc., and does not cover manual switching of airflow rate, as is often the case with fan coil units and indoor units of packaged air conditioners. If variable airflow rate control is used, the minimum airflow rate ratio (ratio to the rated airflow rate) is set, and if the load factor falls below this minimum airflow rate ratio, the value of the coefficient at the minimum load factor where the load factor does not fall below the minimum airflow rate ratio \(f_{AC,ahu,i,j,min}\) is used for the load factor below that. If the load to be handled exceeds the rated capacity (overload), 1.2 is assumed for both constant and variable airflow rate control. Originally, in the case of an overload, the room temperature would deviate from the setpoint without the load being processed, but this calculation method does not reproduce this phenomenon and calculates energy consumption assuming that 1.2 times the rated power consumption was consumed to reach the set temperature and humidity (the load was processed) for the overload condition.

2.5.8 Rated Power Consumption of Single Fan

The rated power consumption of an air handling unit group should be the sum of the power consumption of the fans belonging to the relevant air handling unit group.

Table 61. Input

Variable Name	Description	Unit	Reference
\(N_{AC,ahu,i,j}\)	Number of fans j belonging to the air handling unit group	Number of devices	Form 2-7: (2) Number of Devices
\(E_{AC,ahu,i,j,fsa}\)	Rated power consumption of the supply air fan of fan j belonging to the air handling unit group	kW/device	Form 2-7: (7) Rated Power Consumption of Fan (air supply)
\(E_{AC,ahu,i,j,fra}\)	Rated power consumption of the return air fan of fan j belonging to the air handling unit group	kW/device	Form 2-7: (7) Rated Power Consumption of Fan (return air)
\(E_{AC,ahu,i,j,foa}\)	Rated power consumption of the outside air fan of fan j belonging to the air handling unit group	kW/device	Form 2-7: (7) Rated Power Consumption of Fan (outside air)
\(E_{AC,ahu,i,j,fea}\)	Rated power consumption of the exhaust air fan of fan j belonging to the air handling unit group	kW/device	Form 2-7: (7) Rated Power Consumption of Fan (exhaust)

Table 62. Output

Variable Name	Description	Unit	References
\(E_{AC,ahu,i,j,rated}\)	Rated power consumption of fan j belonging to the air handling unit group	kW	2.5.9

\[ E_{AC,ahu,i,j,rated} = \left( E_{AC,ahu,i,j,fsa} + E_{AC,ahu,i,j,fra} + E_{AC,ahu,i,j,foa} + E_{AC,ahu,i,j,fea} \right) \times N_{AC,ahu,i,j} \]

2.5.9 Power Consumption of Fan

Calculate the power consumption of fans belonging to air handling unit group.

Table 63. Input

Variable Name	Description	Unit	Reference
\(E_{AC,ahu,i,j,rated}\)	Rated power consumption of fan j belonging to the air handling unit group	kW	2.5.8
\(f_{AC,ahu,c,i,j,d}\)	Coefficient determined by the airflow rate control method of fan j belonging to air handling unit group i (cooling)	-	2.5.7
\(f_{AC,ahu,h,i,j,d}\)	Coefficient determined by the airflow rate control method of fan j belonging to air handling unit group i (heating)	-	2.5.7

Table 64. Output

Variable Name	Description	Unit	References
\(E_{AC,ahu,c,i,d}\)	Power consumption during cooling operation of fan belonging to the air handling unit group i on date \(d\)	kW	2.5.10, 2.5.12
\(E_{AC,ahu,h,i,d}\)	Power consumption during heating operation of fan belonging to the air handling unit group i on date \(d\)	kW	2.5.10, 2.5.12

The power consumption in cooling operation \(E_{AC,ahu,c,i,j,d}\) and in heating operation \(E_{AC,ahu,h,i,j,d}\) of fan j in air handling unit group i are calculated by the following formula.

\[ E_{AC,ahu,c,i,j,d} = E_{AC,ahu,i,j,rated} \times f_{AC,ahu,c,i,j,d} \]

\[ E_{AC,ahu,h,i,j,d} = E_{AC,ahu,i,j,rated} \times f_{AC,ahu,h,i,j,d} \]

The power consumptions of the fan belonging to the air handling unit group i \(E_{AC,ahu,c,i,d}\) and \(E_{AC,ahu,h,i,d}\) are calculated by the following formula.

\[ E_{AC,ahu,c,i,d} = \sum_{j} E_{AC,ahu,c,i,j,d} \]

\[ E_{AC,ahu,h,i,d} = \sum_{j} E_{AC,ahu,h,i,j,d} \]

2.5.10 Fan Heat Generation

Calculate the heat generation by the fans of the air handling unit group.

Table 65. Input

Variable Name	Description	Unit	Reference
\(ACType_{i,j}\)	Air conditioner type of air conditioner j belonging to the air handling unit group	-	Form 2-7: (3) Air Conditioner Type
\(T_{AC,ahu,i,d}\)	Operating hours of the air handling unit group i on date \(d\)	h/d	2.5.2
\(T_{AC,ahu,c,i,d}\)	Cooling operation hours of the air handling unit group i on date \(d\)	h/d	2.5.2
\(T_{AC,ahu,h,i,d}\)	Heating operation hours of the air handling unit group i on date \(d\)	h/d	2.5.2
\(E_{AC,ahu,c,i,d}\)	Power consumption during cooling operation of fan belonging to the air handling unit group i on date \(d\)	kW	2.5.9
\(E_{AC,ahu,h,i,d}\)	Power consumption during heating operation of fan belonging to the air handling unit group i on date \(d\)	kW	2.5.9
\(L_{AC,ahu,c,i,d}\)	Load factor during cooling operation of the air handling unit group i on date \(d\)	-	2.5.6
\(L_{AC,ahu,h,i,d}\)	Load factor during heating operation of the air handling unit group i on date \(d\)	-	2.5.6

Table 66. Output

Variable Name	Description	Unit	References
\(Q_{AC,ahu,heat,c,i,d}\)	Fan heat generation of the air handling unit group i on date \(d\) (during chilled water operation)	MJ/d	2.6.1
\(Q_{AC,ahu,heat,h,i,d}\)	Fan heat generation of the air handling unit group i on date \(d\) (during hot water operation)	MJ/d	2.6.1

The heat generations by the fans of an air handling unit group \(Q_{AC,ahu,heat,c,i,d}\) and \(Q_{AC,ahu,heat,h,i,d}\) are calculated by the following formula. Note that the heat generation should be included only when the type of air conditioner belonging to the air handling unit group i is "air conditioner".

where \(ACExists_{i}\) is a boolean value that is True if at least one of the air conditioner types of air conditioner j belonging to air handling unit group i \(ACType_{i,j}\) is "air conditioner", and is False otherwise.

Also, \(f_{fan,heat}\) is the fan heat generation ratio.

a) If "air conditioner" is included in the types of air conditioners belonging to the air handling unit group i ( \(ACExists_{i} = {\mathrm{True}}\)),

a-1) If the load factor during cooling operation is not negative and the load factor during heating operation is negative, (\(L_{AC,ahu,c,i,d} \geqq 0 \land L_{AC,ahu,h,i,d}<0\) )

\[ Q_{AC,ahu,heat,c,i,d} = f_{fan,heat} \times E_{AC,ahu,c,i,d} \times T_{AC,ahu,c,i,d} \times 3.6 \]

\[ Q_{AC,ahu,heat,h,i,d} = f_{fan,heat} \times E_{AC,ahu,h,i,d} \times T_{AC,ahu,h,i,d} \times 3.6 \]

a-2) If the load factor during cooling operation is not negative and the load factor during heating operation is not negative, (\(L_{AC,ahu,c,i,d} \geqq 0 \land L_{AC,ahu,h,i,d} \geqq 0\) )

\[ Q_{AC,ahu,heat,c,i,d} = f_{fan,heat} \times (E_{AC,ahu,c,i,d} + E_{AC,ahu,h,i,d} ) \times T_{AC,ahu,i,d} \times 3.6 \]

\[ Q_{AC,ahu,heat,h,i,d} = 0 \]

a-3) If the load factor during cooling operation is negative and the load factor during heating operation is negative, (\(L_{AC,ahu,c,i,d} < 0 \land L_{AC,ahu,h,i,d} < 0\) )

\[ Q_{AC,ahu,heat,c,i,d} = 0 \]

\[ Q_{AC,ahu,heat,h,i,d} = f_{fan,heat} \times (E_{AC,ahu,c,i,d} + E_{AC,ahu,h,i,d}) \times T_{AC,ahu,i,d} \times 3.6 \]

a-4) If the load factor during cooling operation is negative and the load factor during heating operation is not negative, (\(L_{AC,ahu,c,i,d} < 0 \land L_{AC,ahu,h,i,d} \geqq 0\) )

\[ Q_{AC,ahu,heat,c,i,d} = f_{fan,heat} \times E_{AC,ahu,h,i,d} \times T_{AC,ahu,c,i,d} \times 3.6 \]

\[ Q_{AC,ahu,heat,h,i,d} = f_{fan,heat} \times E_{AC,ahu,c,i,d} \times T_{AC,ahu,h,i,d} \times 3.6 \]

b) In other cases,

\[ Q_{AC,ahu,heat,c,i,d}=0 \]

\[ Q_{AC,ahu,heat,h,i,d}=0 \]

2.5.11 Total Heat Exchanger Power Consumption

Calculate the power consumption of the total heat exchangers belonging to air handling unit group i.

Table 67. Input

Variable Name	Description	Unit	Reference
\(E_{AC,ahu,aex,R,i,j}\)	Rated power consumption of the total heat exchanger rotor of fan j belonging to air handling unit group	kW/device	Form 2-7: (19) Rotor Power Consumption
\(N_{AC,ahu,i,j}\)	Number of air conditioners j belonging to the air handling unit group	Number of devices	Form 2-7: (2) Number of Devices

Table 68. Output

Variable Name	Description	Unit	References
\(E_{AC,ahu,aex,i,d}\)	Power consumption of the total heat exchanger rotor belonging to the air handling unit group	kW	2.5.12

The power consumption of a total heat exchanger belonging to the air handling unit group i \(E_{AC,ahu,aex,i,d}\) is calculated by the following formula.

\[ E_{AC,ahu,aex,i,d} = \sum_{j} \left( E_{AC,ahu,aex,R,i,j} \times N_{AC,ahu,i,j} \right) \]

2.5.12 Annual Primary Energy Consumption of an Air Handling Unit Group

Calculate the annual primary energy consumption of an air handling unit group.

Table 69. Input

Variable Name	Description	Unit	Reference
\(E_{AC,ahu,c,i,d}\)	Power consumption during cooling operation of fan belonging to the air handling unit group i on date \(d\)	kW	2.5.9
\(E_{AC,ahu,h,i,d}\)	Power consumption during heating operation of fan belonging to the air handling unit group i on date \(d\)	kW	2.5.9
\(E_{AC,ahu,aex,i,d}\)	Power consumption of the total heat exchangers belonging to the air handling unit group	kW	2.5.11
\(T_{AC,ahu,c,i,d}\)	Air conditioning operation hours of (cooling) air handling unit group i on date \(d\)	h/d	2.5.2
\(T_{AC,ahu,h,i,d}\)	Air conditioning (heating) operation hours of an air handling unit group i on date \(d\)	h/d	2.5.2
\(T_{AC,ahu,aex,i,d}\)	Operating hours of the total heat exchangers of the air handling unit group i on date \(d\)	h/d	2.5.2
\(L_{AC,ahu,c,i,d}\)	Load factor during cooling operation of the air handling unit group i on date \(d\)	-	2.5.6
\(L_{AC,ahu,h,i,d}\)	Load factor during heating operation of the air handling unit group i on date \(d\)	-	2.5.6

Table 70. Output

Variable Name	Description	Unit	References
\(E_{AC,ahu,i}\)	Annual primary energy consumption of the air handling unit group	MJ/year	2.8

The annual primary energy consumption of an air handling unit group \(E_{AC,ahu,i}\) is calculated by the following formula.

\[ E_{AC,ahu,i} = \left( E_{AC,ahu,c,i} + E_{AC,ahu,h,i} + E_{AC,ahu,aex,i} \right) \times 3600 \times 10^{-3} \times f_{prim,e} \]

where \(E_{AC,ahu,c,i}\) and \(E_{AC,ahu,h,i}\) are calculated by the following formula.

\[ E_{AC,ahu,c,i} = \sum_{d=1}^{365} \left\{ \max(C_{i,d}, 0) + \max(H_{i,d}, 0) \right\} \times 10^{-3} \]

\[ E_{AC,ahu,h,i} = \sum_{d=1}^{365} \left\{ \max(-C_{i,d}, 0) + \max(-H_{i,d}, 0) \right\} \times 10^{-3} \]

\[ C_{i,d} = \begin{cases} 0 & ,\left( L_{AC,ahu,c,i,d} = 0 \right) \\[6pt] E_{AC,ahu,c,i,d} \times T_{AC,ahu,c,i,d} \times \dfrac{L_{AC,ahu,c,i,d}}{|L_{AC,ahu,c,i,d}|} & ,\left( \text{otherwise} \right) \end{cases} \]

\[ H_{i,d} = \begin{cases} 0 & ,\left( L_{AC,ahu,h,i,d} = 0 \right) \\[6pt] E_{AC,ahu,h,i,d} \times T_{AC,ahu,h,i,d} \times \dfrac{L_{AC,ahu,h,i,d}}{|L_{AC,ahu,h,i,d}|} & ,\left( \text{otherwise} \right) \end{cases} \]

where \(E_{AC,ahu,aex,i}\) is calculated by the following formula.

\[ E_{AC,ahu,aex,i} = \sum_{d=1}^{365} \left( E_{AC,ahu,aex,i,d} \times T_{AC,ahu,aex,i,d} \right) \times 10^{-3} \]