On the basis of the calculated heating water flow rate, the pressure
drop on the heating water side can now be calculated as described in
the example on page 22 and with the aid of the diagram for
Vitocell 300-V (type EVI).
Result:
Pressure drop on the heating water side of the DHW cylinder =
80 mbar (8 kPa).
Cylinder loading systems — Vitocell 100-L with Vitotrans 222
5.1 Applications and advantages
The Viessmann cylinder loading system is a combination of a Vitocell
100-L DHW cylinder and a modular Vitotrans 222 heat exchanger
set.
The cylinder loading system for DHW heating is a preferred choice for
the following applications and conditions:
■ Heating circuits requiring low return temperatures or ones where the
return temperatures are limited, e.g. for district heating or condens-
ing boilers.
The heating/final temperature (10/60 ºC) is achieved in one pass
through the Vitotrans 222 heat exchanger. The wide DHW spread
leads to a low return temperature on the primary side. This brings
advantages through high condensation rates when utilising con-
densing technology.
■ Large cylinder capacities with offset heating and draw-off times,
e.g. water is drawn off in bursts at schools, sports centres, hospitals,
army barracks, social buildings, apartment buildings, etc.
■ Short-term peak loads, i.e. high draw-off rates and varying reheat
times, e.g. DHW heating in swimming pools, sports facilities, indus-
trial enterprises, and abattoirs.
■ Limited space as the cylinder loading system can transfer a high
output.
Vitocell 100-L with Vitotrans 222
■ Corrosion-resistant cylinder made from steel, with Ceraprotect
enamel coating. Additional cathodic protection via a magnesium
anode; impressed current anode available as an accessory.
■ Easy handling through low weight and removable thermal insulation.
■ Low heat losses through high grade, all-round thermal insulation.
■ No critical germination zones through thorough heating of the entire
water content.
■ In conjunction with the Vitotrans 222 heat exchanger set (accesso-
ries) as a cylinder loading system, particularly suitable for combina-
tion with condensing boilers.
■ Accurate cylinder heating to the right degree even with modulating
flow temperature.
■ Vitotrans 222, comprising a plate heat exchanger, highly efficient
cylinder loading pump and heating water pump, available as an
accessory.
■ Electric immersion heater and heating lance for use in conjunction
with heat pumps, available as accessories.
5.2 Function description of the cylinder loading system
Operation with modulating flow temperature
During the cylinder heating process (no draw-off), cylinder loading
pump
R
within the cylinder loading system withdraws cold water
T
from the bottom 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 strata inside the DHW cylinder, cylinder
loading pump
R
will only be switched on if temperature sensor
L
signals that the set temperature has been reached.
The required heat exchanger transfer output is set by the line regulat-
ing valve
O
.
Mixer assembly
N
(accessories) mixes the heating water on the pri-
mary side in accordance with the set DHW temperature. A set DHW
temperature of max. 60 ºC prevents scaling of the plate heat
exchanger.
Pasteurisation (controlling legionella bacteria) is feasible in conjunc-
tion with Viessmann boilers with the Vitotronic boiler control units or
with the Vitotronic 200-H heating circuit control units (accessories).
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.
Either at the end of drawing or whilst DHW is drawn off, the cylinder
volume is reheated to its 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.
Bearing in mind the stated set heating water and DHW temperatures,
the Vitotrans 222 heat exchanger set can be operated up to a total
hardness of 20 ºdH (total of alkaline earths 3.6 mol/m
3
).
Sizing
(cont.)
24
VIESMANN
DHW heating
5
5414 646 GB
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