Hitachi YUTAKI S80 Series Technical Catalogue page 73

4. Capacity and selection data
As the heating load has fallen to 9.0 kW as we are considering this point as regular heating load, it may be reselected
the needed unit. The RAS-5H(V)RNME-AF + RWH-5.0FS(V)NFE system would provide too much heating capacity so we
could take the RAS-4H(V)RNME-AF + RWH-4.0FS(V)NFE system for these new conditions.
RAS-4H(V)RNME-AF + RWH-4.0FS(V)NFE

RAS-6H(V)RNME-AF + RWH-6.0FS(V)NFE
RAS-6H(V)RNME-AF + RWH-6.0FS(V)NFE
The maximum heating capacity for this new system for an ambient temperature of -5 ºC WB and a water inlet/outlet tem-
perature of 47/55 ºC is 13.4 kW. We follow the same procedure as in point a.i) to apply the correction and the resulting
heating capacity for this system is 11.43 kW.
By help of the Maximum heating capacity tables the heating capacity for the new system has to be calculated for the cold-
est days conditions (-10ºC).
The maximum heating capacity for an ambient temperature of -10 ºC WB and a water inlet/outlet temperature of 47/55 ºC
is 13.0 kW.
• Step 2: Heating capacity correction for defrost and piping length
The actual heating capacity for the system selected in the coldest days of the year is calculated by applying correction fac-
tors for defrost and piping length, following the method used above.
Q : Actual heating capacity (kW)
H
Q : Maximum heating capacity (kW)
MH
f : Defrost correction factor
D
f : Heating piping length correction factor
LH
f
- Calculation of :
D
The resulting defrost correction factor for our outdoor ambient temperature of -10ºC WB is 0.89.
f
- Calculation of :
LH
The resulting piping length correction factor is 0.992.
- Calculation of :
Q
H
Once the correction factors to be applied have been determined, the formula for actual heating capacity
of the unit RAS-4H(V)RNME-AF + RHM-4.0FS(V)NFE system can be applied:
Q = 13.0 kW x 0.89 x 0.992 = 11.47 kW
H
73
TCGB0075 rev.0 - 11/2012
YUTAKI S80
Q = Q x f x f
H MH D LH
Maximum heating capacity (kW)
13.4
16.0
17.9
4