Viessmann Vitodens 222-F B2TB, Application Manual

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Product Information
Storage Tank Loading System (STLS)
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One key aspect of the Vitodens 222-F is its unique approach to
meeting varying loads of DHW demands. The Advanced Storage Tank
Loading System (STLS) technology ensures a reliable and efficient
DHW supply by combining storage and tankless technology. The
STLS utilizes a plate heat exchanger and innovative piping strategy to
combine the benefits of both a storage type water heater and on-de-
mand DHW. This allows the 222-F to meet a varying range of loads
from small to large without affecting the operation of the boiler.
Here’s how it works:
Micro DHW Loads
A demand for DHW is where the 222-F starts to outshine all other
products on the market. Imagine you turn the hot water tap on to
rinse a glass, or better yet trickle a little bit of hot water while you
shave. A typical on demand type water heater would short cycle or
may not even turn on for such a small amount of DHW. The 26 gallon
storage tank on the 222-F addresses this by simply storing a small
amount of hot water(1) for these types of situations. Therefore the
small volume of hot water(2) is taken from the onboard storage tank
preventing the boiler from short cycling and eliminating common is-
sues with on demand units. This will also allow the boiler to continue
to provide heat to the heating system uninterrupted(3).
Heating Mode
In heating mode the boiler functions in the exact same way as a
typical low mass hi efficiency condensing gas boiler. The internal
circulator(1) draws in cool return water from the system(2), pushes
it through the boiler where it is heated up and sent back out into the
system(3).