Viessmann VITOCELL 100-U - Calculation of the Cylinder Size Based on Water Volume; Calculation of the Cylinder Size Based on Heat Volume; 6 Installation - DHW Cylinders 6.1 Connection on the DHW Side

Calculation of the cylinder size based on water volume
Over a period of 30 min, a total water volume V
ttl
at a temperature of
40 ºC is required.
V
ttl.
= n
Z
· ´ · t
= 8 showers · 15 l/min · 30 min
= 3600 l
Of the 3600 l, the 100 kW connected load can deliver a water volume
V
D
over a period of 30 min.
L · t
V
D
=
c · ΔT
100 kW · 0.5 h · 860 l · K
V
D
=
1 kWh · (40 – 10) K
=1433 l
This means that the DHW cylinder must make the following water vol-
ume available at a temperature of 40 ºC:
3600 l – 1433 l = 2167 l
At a storage temperature of 60 ºC, the required cylinder volume V
cyl
results.
V
cyl.
=
(60 – 10) K
2167 l · (40 – 10) K
=1300 l
The calculated number n of Vitocell 100-L with a volume of 750 l each
results from the following:
n =
750 l
1300 l
= 1.73
Selected cylinder loading system:
2 Vitocell 100-L, each with 750 l cylinder capacity, and 1 Vitotrans 222
heat exchanger set with a heating output of 120 kW (in accordance
with max. available boiler output according to the sample calculation,
i.e. 100 kW).
Calculation of the cylinder size based on heat volume
Over a period of 30 min (as per calculation), a total water volume of
3600 l at a temperature of 40 ºC is required. This corresponds to a heat
volume of Φ
ttl.
.
Φ
ttl.
= V
ttl.
· ΔT · c
1 kWh
= 3600 l · 30 K ·
860 l · K
= 126 kWh
The connected load can, over the drawing period of 30 min, provide a
heat volume of Φ
D
.
Φ
D
= L · t
= 100 kW · 0.5 h = 50 kWh
This means that the DHW cylinder must store a heat volume of Φ
cyl
.
Φ
cyl.
= Φ
ttl.
– Φ
D
= 126 kWh – 50 kWh = 76 kWh
Each individual Vitocell 100-L DHW cylinder with 750 l cylinder
capacity stores the following heat volume Φ
cyl. ind.
:
860 l · K
Φ
cyl. ind.
= 750 l · (60 – 10) K ·
1 kWh
= 43.6 kWh
This results in the calculated number of cylinders n.
43.6 kWh
n =
Φ
cyl. ind.
Φ
cyl.
76 kWh
= = 1.74
Selected cylinder loading system:
2 Vitocell 100-L, each with 750 l cylinder capacity, and 1 Vitotrans 222
heat exchanger set with a heating output of 120 kW (in accordance
with max. available boiler output according to the sample calculation,
i.e. 100 kW).
Installation — DHW cylinders
6.1 Connection on the DHW side
See the diagrams from page 31 or 38 regarding the connection on
the DHW side of DHW cylinders installed as a cylinder bank.
Note
Dishwashers and washing machines can be connected to the central
hot water supply.
Washing machines must have separate cold and hot water connec-
tions. By supplying hot water directly from the DHW cylinder, the elec-
trical heating of the water in the dishwasher or washing machine is
reduced. This saves time, energy and costs. Please follow the manu-
facturer's recommendations.
The DHW temperature in the piping downstream must be limited to
60 ºC (according to the EnEV [Germany; check local regulations])
through the installation of a suitable mixing device, e.g. a thermostatic
mixing valve. This does not apply to DHW systems that demand higher
temperatures for their intended use or that require a pipe length of less
than 5 m.
Please note:
Consult the relevant manufacturer's installation instructions when fit-
ting thermostatic mixing valves. The mixing device does not prevent
the risk of scalding at the draw-off point. The installation of a mixer tap
at the draw-off point is essential.
Only for cylinder banks Vitocell 300-H:
With DHW outlet temperatures in excess of 60 ºC, the connecting line
on the DHW side can, in multi cylinder banks, also be connected in
series. Connect the connection line on the heating water side as shown
in the diagrams on page 36.
Cylinder loading systems — Vitocell 100-L with Vitotrans 222
(cont.)
28
VIESMANN
DHW heating
6
5414 646 GB