Hitachi YUTAKI S80 Series - Page 75

4. Capacity and selection data
TCGB0075 rev.0 - 11/2012
75
4
b) Selection of the Domestic Hot Water Tank accessory
The Domestic Hot Water Tank accessory applicable to the YUTAKI S80 system is the DHWS195S-2.0H1E or DHWS260S-
2.0H1E depending on the water demand and the combination system. In order to meet the suitable tank it is necessary to
estimate the daily domestic hot water demand. The following expression is used to calculate this consumption:
D
i
(T)= D
i
(60ºC) x (60-T
i
/ T-T
i
)
Where:
D
i(T): Water demand at T temperature.
D
i(60ºC):Domestichotwaterdemandat60ºC.
T: Domestic hot water tank’s temperature.
T
i: Inlet cold water temperature.
- Calculation of D
i(60ºC):
To calculate the domestic hot water demand at 60ºC, Di(60ºC), it must be referred the current technical
installation legislation of the country where the installation will be performed, in order to know the standard
liters per person each day. This is necessary to estimate the consumption in relation with the users of the
installation. For the next example the domestic hot water demand at 60º it has been taken 30 liters per
person, in a detached house with 4 persons (3 bedrooms).
- Calculation of T:
The domestic hot water tank’s temperature should be estimated. It is referred to the accumulated water
temperature inside the tank, before the use. Habitually the temperature’s rank is between 45ºC - 65ºC. In
the example below, it has been taken 45ºC.
- Calculation of T
i:
The inlet cold water temperature is the temperature of the water that is lling the tank. The cold water
rank’s temperature is 10ºC - 15ºC. To calculate an approximate water demand it has been used 12ºC.
- Example:
D
i
(T)= 120 x (60-12 / 45-12) = 174.6litres/day(*)
N O T E
(*):Dependingontheelectrictariff,theinstallationspaceandthecost/efciencyrelationtherearedifferent
strategies of accumulation to follow. In case a low cost electric tariff strategy is choosen (accumulation strat-
egy) the daily water demand could double the normal case (semiaccumulation strategy).
The election of the water tank depends on the next table:
Daily water demand Domestic Hot Water Tank
<185 Litres DHWS195S-2.0H1E
>185 Litres DHWS260S-2.0H1E
YUTAKI S80 Domestic Hot Water Tank
RAS-(4/5/6)H(V)RNME-AF + RWH-(4.0/5.0/6.0)FS(V)NFE
DHWS195S-2.0H1E
DHWS260S-2.0H1E
N O T E
• The storage capacity of the tank has to meet with the daily consumption in order to avoid stagnation of water.
• The YUTAKI S80 is designed for combination with HITACHI Domestic Hot Water Tank. In case of another tank
is being used in combination with YUTAKI S80, HITACHI cannot guarantee neither good operation or reliability
of the system.
• This Domestic Hot Water Tank selection procedure is just orientated, be sure of consulting the local legislation
to ensure a good water demand value.