Viessmann Vitodens 222-F B2TB, Application Manual

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Product Information
Storage Tank Loading System (STLS))
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Entering DHW Mode
After the bottom 1/3 of the hot water is removed from the storage
tank(1), the diverting valve switches from heating mode to DHW(2)
and begins supplying heat to the plate heat exchanger(3). At the
same time, the DHW pump(4) is powered and begins circulating a
predefined amount of domestic water through the plate heat exchang-
er(3.3gpm). When in this mode, there is no circulation to the heating
system and this now gives the DHW load the priority.
Small-Medium DHW Loads (0.5-3.4 GPM)
As a result of the drop tube design in the storage tank(1), the boiler
has the ability to recharge the storage tank and satisfy the DHW
demand simultaneously when under small loads. Heres how this
works; If a DHW load of 1.8 GPM is exiting the boiler(2), then 1.8
GPM of cold water must enter the boiler(3). Now because the DHW
circulator(4) is drawing in 3.3 GPM of cold water, it will take the 1.8g
of fresh water, and the remaining 1.6g will come from the storage
tank(5). Unlike storage sytle water heaters the 222-F tank is charged
from the top-down. This ensures a more consistant supply tempera-
ture and prevents the incoming cold water from diluting the entire
temperature of the storage tank. This is the STLS!
Thermal image of the STLS