Siemens LMU54 Series Basic Documentation page 97

Siemens Building Technologies
HVAC Products
In the case of the stratification storage tank, a differentiation is made between 2 types of
DHW charging modes:
1. Full charging.
2. Recharging.
The criteria for these 2 operating modes are dependent on the compensation variant of
DHW.
• With compensation variant Bw = «RU-dependent»
Full charging is released only when the switching program is in the first DHW forward
shift period of the respective day.
This is transmitted from the QAA73... via bus interface.
Note: Other types of OpenTherm RU do not support this function; this means that
when using an RU of other manufacture, only recharging will be activated.
Release of full charging:
0: Full charging of stratification storage tank locked
1: Full charging of stratification storage tank released
Depending on the DHW mode on the RU (heating program with forward shift of DHW or
own DHW program), full charging is released in 1 of 2 different ways.
1. Full charging during the DHW forward shift against the heating program:
Heating program
Nom.
Red. / frost.
DHW program
Nom.
Red. / frost.
Forward shift
Charging mode
Full charging
Recharging
7494f04E/0102
Charging of stratification storage tank with DHW forward shift
During the DHW forward shift time, the QAA73... sends:
FreigabeDurchladung = 1
This gives rise to the release of the stratification storage tank's full charging. If there are
further changes from «Reduced» to «Nominal level» on the same day, there will be no
more forward shifts. After the first forward shift:
FreigabeDurchladung = 0
This gives rise to the release of the stratification storage tank's recharging.
Basic Documentation LMU54... / LMU64...
7 DHW control (BWR)
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CC1P7494en
07.11.2002