Function Description Of The Cylinder Loading System; Operation With Modulating Flow Temperature; Operation With Constant Flow Temperature - Viessmann Vitocell 300-H Technical Manual

Cylinder loading systems — Vitocell 100-L with Vitotrans 222

5.2 Function description of the cylinder loading system

Operation with modulating flow temperature

During the heating process (no draw-off), loading pump R within
the cylinder loading system withdraws cold water T from the bot-
tom of DHW cylinder U; this is then heated in heat exchanger set
C and resupplied to the top B of the DHW cylinder.
To avoid disturbing the thermal stratification layers inside the DHW
cylinder, cylinder loading pump R will only be switched on if tem-
perature sensor L signals that the set temperature has been
reached.
The required heat exchanger transfer output is set by line regulating
valve O.
Mixer assembly (accessories) N mixes the heating water on the pri-
mary side in accordance with the set DHW temperature. A set DHW
temperature of max. 60 °C prevents scaling of the plate heat
exchanger.
Pasteurisation is feasible in conjunction with Viessmann boilers with
the Vitotronic boiler control units or with the Vitotronic 200-H heating
circuit control units (accessories).
A
B
W
5
V
U
A DHW
B Hot water inlet from the heat exchanger
C Vitotrans 222 heat exchanger set
D Plate heat exchanger
E Heating circuit pump (primary), highly efficient
F Air vent valve
G Heating water flow
H Heating water return
K Boiler
L Temperature sensor

Operation with constant flow temperature

The Vitotrans 222 heat exchanger set is operated without a mixer
assembly. Limit the heating water temperature to 75 °C.
The required DHW temperature and transfer output are set by
adjusting the circulating volume for the heating process according to
the heating output of the heat exchanger at line regulating valve L.
If the available boiler output is below that of the Vitotrans 222, the
setting is done according to the boiler output.
VIESMANN
28
F F F
C
N
P
R
O
S
L
D
T
(cont.)
The base load is covered by the continuous output of the
Vitotrans 222.
Any additional hot water demand during peak times is covered by
the cylinder capacity.
During draw-off and once draw-off has ended, the cylinder volume is
reheated to the set temperature via the Vitotrans 222. In the fully
heated state (no draw-off), cylinder loading pump R and heating
circuit pump E in the Vitotrans 222 are switched OFF.
Provided the above set heating water and DHW temperatures are
observed, the Vitotrans 222 heat exchanger set can be operated up
to a total water hardness of 20 °dH (total of alkaline earths
3.6 mol/m 3 ).
F
G
H
E
N Mixer assembly
O Line regulating valve
P Non-return valve
R Cylinder loading pump (secondary), highly efficient
S Safety valve, does not replace the DHW cylinder safety valve to
DIN 1988.
T Shared cold water connection with safety assembly to DIN 1988
U Vitocell 100-L, (here: 500 l capacity)
V Lower cylinder temperature sensor (OFF)
W Upper cylinder temperature sensor (ON)
High or medium draw-off rates are covered by the DHW cylinder.
Cold water flows into the DHW cylinder to replace the hot water
drawn. If the cold water layer inside the DHW cylinder reaches upper
temperature controller T, the Vitotrans 222 starts.
The base load is covered by the continuous output of the
Vitotrans 222. Any additional hot water demand during peak times is
covered by the cylinder capacity.
K
DHW heating