Hisense Hi-Therma Serie Manual De Instalación Y Mantenimiento página 30

SPACE HEATING AND DHW
8.4 DHW TANK SELECTION AND
INSTALLATION
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N O T E
• This DHW tank is designed for heat pump type heating system. DHW
shall be selected according to the requirements in this instruction and
on-site use requirements.
• If the selection, installation and wiring are not carried out according
to the requirements in this instruction, we would not be responsible
for the problems caused by the DHW tank.
•
Hot water may cause serious burns. Test water temperature with
hands. Use after the water is mixed till proper temperature.
•
Connecting of water pipe with tap water pipe should be operated by
qualified staff using proper piping material according to local
regulations and standards.
•
When the high domestic hot water temperature can be a potential
risk for human injuries, a mixing valve (field supplied) shall be
installed at the hot water outlet connection of the DHW tank. This
mixing valve shall secure that the hot water temperature at the hot
water tap never rise above a set maximum value. This maximum
allowable hot water temperature shall be selected according to the
applicable legislation.
8.4.1 DHW tank selection
When selecting a tank for DHW operation, take into considera-
tion the following points:
- The volume of the tank has to meet with the daily consumption
in order to avoid stagnation of water.
- Fresh water must circulate inside the DHW tank water circuit
at least one time per day during the first days after the
installation has been performed. Additionally, flush the system
with fresh water when there is no consumption of DHW during
long periods of time.
- Try to avoid long runs of water piping between the tank and
the DHW installation in order to decrease possible
temperature losses.
- lf the domestic cold water entry pressure is higher than the
equipment's design pressure, a adequate pressure reducer
must be installed to ensure that the maximum pressure is
NOT exceeded.
1 Storage capacity
The storage capacity of the DHW tank depends on the daily
water demand and the combination method. The daily water
demand is estimated with the following calculation formula for
consumption:
D (T)= D (60 ºC) x (60-T
i i
Where:
D (T):
Water demand at T temperature
i
D (60ºC): Domestic hot water demand at 60 ºC
i
T: Temperature of the DHW tank
T :
Temperature of the inlet cold water
i
- Calculation of D (60 ºC):
i
The standard consumption, expressed in daily litres per person
and determined by technical installation regulations of each
country, is used to calculate the domestic hot water demand at
60 ºC, D (60 ºC). This quantity is then multiplied by the expected
i
number of users of the installation. In the following example, the
domestic hot water demand at 60 ºC has been considered as 30
litres per person, in a detached house with 4 residents.
/ T-T )
i i
Calculation of T:
-
The temperature of the DHW tank refers to the temperature of
the accumulated water inside the tank, prior to operation. This
temperature is usually between 45 ºC and 65 ºC. It has been
considered as 45 ºC in this example.
Calculation of T :
-
i
The temperature of the inlet cold water refers to the
temperature of the water being supplied to the tank. Since this
temperature is usually between 10 ºC and 15 ºC, it has been
considered as 12 ºC in this example.
Example:
-
(T)= 30 x 4 x (60-12 / 45-12) = 174.5 litres/day
D
i
174.5 x 2(*) = 349 litres/day approximate demand of hot water
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N O T E
(*) It is recommended to multiply the calculated consumption by two, in
case that the installation is in a detached house. This is done to ensure
a steady supply of hot water. In the case of a multifamily installation, it
is not necessary to increase the forecast of hot water demand, given
the lower simultaneity factor.
2 Coil Face Area
The coil face area is a key parameter for DHW tank. To improve
the heating efficiency, the coil face area should be adjusted
according to the capacity.
The coil face area should be no less than the values listed in the
table below.
Storage Capacity(L)
Coil Face Area(m
2
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N O T E
Smaller coil face area will lead to worse heating efficiency. In that
condition, the heat pump will start and stop frequently which causes
more time and more power consumption to heat up the DHW tank.
18
150 200
100
1.5
1.5
1.8
)
250
300
2.0
1.8