Technical Information
Capacities and selection data
TCGB0079 rev.0 - 01/2013
52
the morning and the maximum required loads of room 2 (west zone) occurs at the afternoon.), select the outdoor unit that
cover the maximum simultaneous load on the installation and check that the total combination horsepower must not be
higher than the limits, using the following:
Total combination horsepower = (Total indoor unit horsepower / Outdoor unit horsepower) x 100
4 Calculation of f
LC
(Cooling piping length correction factor)
The length of the refrigerant piping used and the height difference between the outdoor unit and the indoor units directly
affect the performance of the unit. This concept is quantied in the piping length correction factor.
To determine this value it is necessary refer to the piping length correction factor tables that are based on the equivalent
piping length in meter and height between outdoor and indoor units. For the equivalent one-way piping length between
indoor unit and outdoor unit (m) consider the following:
One 90º elbow is 0.5 m.
One 180º bend is 1.5 m.
One Multi-kit is 0.5 m.
5 Cooling capacity correction (Q
C
) due to the piping lenght
The actual cooling capacity of the pre-selected unit must be calculated applying the necessary correction factors:
Q
C
= Q
MC
x f
LC
Q
C
: Actual cooling capacity of the outdoor unit (kW).
Q
MC
: Maximum cooling capacity of the outdoor unit (kW).
f
LC
: Cooling piping length correction factor.
6 Cooling capacity correction of the outdoor unit (
Q
AC
) depending of the humidity of the indoor unit
The correction ratio due to humidity is the coefcient that corrects the sensible heat capacity of a unit according to the rela-
tive humidity of the air entering the indoor unit. The greater the relative humidity the lower will be the sensible heat capacity
and vice versa.
The following formula is used to apply an adjustment to the cooling capacity showed in the tables due to the difference
between the real indoor air inlet dry bulb temperature vs the one used for calculate the nominal cooling capacity data.
Q
AC
=Q
C
+ (CR x (DB
R
- DB))
Q
AC
: Actual cooling capacity of the outdoor unit (kW) (at given real % humidity)
Q
C
: Corrected cooling capacity of the outdoor unit by piping length (kW) (at given 50 % humidity)
CR: Correction ratio due to humidity.
DB
R
: Real Dry Bulb evaporator temperature (ºC).
DB: Dry Bulb evaporator temperature (ºC) for each wet bulb temperature from the curves (HR = 50 %).
7 Actual indoor units capacity
Once it is known the actual outdoor units cooling capacity, it must be calculated the actual cooling capacity of each indoor
unit, according to the following formula:
Q
CI
= Q
AC
x (Q
NCI
/ Q
NCC
)
Q
CI
: Actual cooling capacity of the indoor unit (kW).
Q
AC
: Actual cooling capacity of the outdoor unit (kW).
Q
NCI
: Nominal cooling capacity of the indoor unit (kW).
Q
NCC
: Nominal cooling capacity of the combination (kW).
8 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
CI
x SHF
SHC: Sensible heat capacity (kW).
Q
CI
: Actual cooling capacity of the indoor unit (kW).
SHF: Sensible heat factor.
TCGB0079_rev0_11-2012.indb 52 29/01/2013 14:27:02