Viessmann VITOCELL 100-U - General Formulas for Calculating the Cylinder Loading System; Sample Calculation

M
A
B
AB
A
P
O
N
E E E E
F
G
M
L
K
D
C
B
H
A
DHW
B
Hot water inlet from the heat exchanger
C
Heating lance
D
Plate heat exchanger
E
Air vent valve
F
Heating water flow from the heat pump
G
Heating water return to the heat pump
H
Heat pump
K
Line regulating valve
L
Non-return valve
M
Cylinder primary pump
N
Common cold water connection with safety assembly to
DIN 1988
O
Vitocell 100-L
P
Cylinder temperature sensor of the heat pump
5.3 General formulas for calculating the cylinder loading system
With reference to EN 12831, Q = Φ is used for heat volume and
²
= L for heating output (continuous output) instead of the values cur-
rently used by DIN 4701 .
Calculation based on water volume
L · t
V
D
=
c · ΔT
in l
V
ttl.
= V
D
+ V
cyl.
in l
= n
Z
· ´ · t in l
Calculation based on heat volume
Φ
D
= L · t in kWh
Φ
ttl.
= V
ttl.
· ΔT · c in kWh
= Φ
cyl.
+ Φ
D
in kWh
= V
ttl.
· ΔT · c = Φ
cyl.
+ Φ
D
Φ
cyl.
= V
cyl.
· c · (T
a
– T
e
) in kWh
5.4 Sample calculation
A sports centre is equipped with 16 showers which are limited to
15 l/min.
According to design requirements, 8 showers are operated simulta-
neously for up to 30 min continuously. The drawing temperature
should be 40 ºC. A max. of 100 kW boiler output is available for DHW
heating.
c = Spec. thermal capacity
1 kWh
860 l · K
n = Number of DHW cylinders
n
Z
= Number of draw-off points
Φ
D
= Heat volume in kWh available by continuous out-
put
L = Continuous output in kW
Φ
ttl.
= Total heat demand in kWh (for production and de-
mand)
Φ
cyl.
= Useable heat volume of the total cylinder capacity
in kWh
Φ
cyl. ind.
= Useable heat volume of a single DHW cylinder in
kWh
t = Time in h
T
a
= Cylinder storage temperature in ºC
T
e
= Cold water inlet temperature in ºC
ΔT = Temperature differential between draw-off temper-
ature and cold water inlet temperature in K
´ = Draw-off rate per draw-off point in l/h
V
D
= DHW heated by continuous output in l
V
ttl
= Total draw-off volume in l
V
cyl
= Useable cylinder capacity in l
Cylinder loading systems — Vitocell 100-L with Vitotrans 222
(cont.)
DHW heating
VIESMANN
27
5414 646 GB
5