Selection Procedure (Step 2) - Hitachi UTOPIA R32 Series Technical Catalogue

4 Capacities and selection data
System selection procedure
9 Sensible heat capacity (SHC)
Once the calculation of the indoor units cooling capacity has been completed, the sensible heat capacity can be
calculated using the following formula:
SHC = Q x SHF
CI
SHC: Sensible heat capacity (kW).
: Actual cooling capacity of the indoor unit (kW).
Q
CI
SHF: Sensible heat factor.
10 Cheks
Check that the total capacity and sensible heat capacity (SHC) are greater than the estimated cooling load by the
different rooms to be conditioned. Therefore, it can be said that the selected outdoor unit meets the minimum cooling
requirements set for the system.
Corrected total cooling capacity (kW)
Corrected sensible heat capacity (kW)
Corrected total cooling capacity (kW)
Corrected sensible heat capacity (kW)

4.2.2 Selection procedure (step 2)

1 Calculate the heating requirements for each room
See if the pre-selected indoor units and outdoor units have the necessary nominal heating capacity for each room.
2 Heating capacity correction (Q
The actual heating capacity of the pre-selected outdoor unit (in cooling mode (step 1)) must be calculated applying
the necessary correction factors:
Q =Q x f x f x f
H MH LH D AL
Q : Actual heating capacity of the outdoor unit (kW)
H
Q : Maximum heating capacity of the outdoor unit (kW)
MH
: Heating piping length correction factor
f
LH
f : Defrost correction factor
D
f : Corrections factor according to altitude.
AL
Calculation of f
LH
Referring to the diagrams for
Calculation of f
D
In situations where the ambient temperature is lower than 7 ºC DB, frost may build up on the heat exchanger. In this
case, the heating capacity for the unit may be reduced because of the time spent by the unit in removing the frost up.
The defrost correction factor takes this time into account to apply the heating capacity correction.
3 Heating capacity of each indoor unit (Q
Once the real heating capacity of the outdoor unit has been determined, its heating capacity in combination with the
indoor units, can be calculated.
Q = Q x (Q / Q )
HI H NHI NHC
: Actual heating capacity of the indoor unit (kW).
Q
HI
Q : Actual heating capacity of the outdoor unit (kW)
H
Q : Nominal heating capacity of the indoor unit (kW)
NHI
Q : Nominal heating capacity of the combination (kW)
NHC
If the corrected heating capacity is greater than the estimated heating load by the different rooms to be conditioned, it
can be said that the selection is valid for both cooling and heating.
Actual heating capacity (kW)
Actual heating capacity (kW)
52 TCGB0136 rev.1 - 05/2021
≥ Estimated total cooling load (kW)
TOTAL
≥ Estimated sensible heat capacity (kW)
TOTAL
≥ Estimated total cooling load (kW)
ROOMn
≥ Estimated sensible heat capacity (kW)
ROOMn
)
H
"4.6 Piping length correction factor (fLC, fLH)".
)
H
≥ Estimated heating capacity (kW)
TOTAL
≥ Estimated heating capacity (kW)
ROOMn
TOTAL
TOTAL
ROOMn
ROOMn
TOTAL
ROOMn