Boiler Supplement Z K - Viessmann Vitocell 300-H Technical Manual

Sizing
(cont.)
Calculating the demand of residential units with centralised supply
systems
5 5.0
Σ n = 25
i
Σ(n · p · v · w ) 676710
v
N = = = 33.2
3.5 · 5820 20370
Now use the calculated demand factor N = 33.2 to select the
required DHW cylinder from the tables in the relevant datasheets at
the available heating water flow temperature (e.g. 80 °C) and a cylin-
der storage temperature of 60 °C. Select a DHW cylinder with an N
factor at least equal to N.
Note
The performance factor N varies subject to the following variables:
L
■ Flow temperature
■ Storage temperature
■ Available or transferable output
For deviating operating conditions, modify the performance factor N
from the values shown in the tables in the relevant datasheets.
Boiler supplement Z
K
According to DIN 4708-2 and VDI 3815, the rated heating output of a
boiler must be increased by the boiler supplement Z
DHW heating demand (see table 6).
Observe the explanations in DIN/VDI [or local regulations].
DIN 4708 specifies 3 main demands for the rated heating output
of the heat source:
Demand 1
The performance factor must be at least equal to or greater than the
demand factor:
N ≥ N
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Demand 2
Only if the rated boiler heating output ²
equal to the continuous output, can the DHW cylinder deliver the
performance factor N stated by the manufacturer:
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≥ ² or Φ ≥ Φ
²
K D K D
Demand 3
Heat generating systems used for both DHW and central heating
must cover the additional output Z
Φ EN 12831 (previously DIN 4701):
HL buil.
Φ ≥ Φ + Z
K HL buil. K
On the basis of DIN 4708-2, VDI 3815 is used for calculating a sup-
plement to the rated boiler heating output as a function of the
demand factor N and a minimum cylinder capacity (see table 6).
It has proved successful in practice to take the boiler supplement
into account according to the following relations:
Φ ≥ Φ · ϕ + Z
K HL buil. K
ϕ = Factor for utilisation of building heating (all rooms heated)
Number of residential units per building
Up to 20
21 to 50
> 50
DHW heating
5 4.3 21.5
Σ (n · p · v · w
to cover the
K
or Φ is higher or at least
K K
as well as the standard heat load
K
ϕ
0.9
0.8
Project no:
Part no:
1 NB2 6510
(0.5) NB1 5820
) = 676710 Wh
v
Possible DHW cylinders:
■ From the Vitocell 300-H datasheet:
Vitocell 300-H with 700 l capacity (N
prising 2 x Vitocell 300-H, each with 350 l capacity
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■ From the Vitocell 300-V datasheet:
Vitocell 300-V with 600 l capacity (N
comprising 2 × Vitocell 300-V, each with 300 l capacity
Selected DHW cylinder:
2 × Vitocell 300-V, each with 300 l capacity.
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Table 6 – Boiler supplement Z
Demand factor N
1
2
3
4
5
6
7
8
9
10
12
14
16
18
20
22
24
26
28
30
40
50
60
80
100
120
150
200
240
300
1
Note
In buildings with an extremely low heat load Φ
be carried out to determine whether the output of the heat source,
including supplement Z , is sufficient for the selected performance
K
factor. It may be necessary to select a larger DHW cylinder.
6510 139965
5820 62565 50 % w
per Tab. 3
on page 15
= 35) as cylinder bank com-
L
= 34.8) as cylinder bank
L
K
Boiler supplement Z
K
in kW
, a check must
HL buil.
VIESMANN
as
v
4
3.1
4.7
6.2
7.7
8.9
10.2
11.4
12.6
13.8
15.1
17.3
19.5
21.7
23.9
26.1
28.2
30.4
32.4
34.6
36.6
46.7
56.7
66.6
85.9
104.9
124.0
152.0
198.4
235.2
290.0
17