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Siemens Building Technologies
Basic Documentation LMU54... / LMU64...
CC1P7494en
HVAC Products
7 DHW control (BWR)
07.11.2002
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:
DHW program
t
Nom.
Red. / frost.
Charging mode
t
Full charging
Recharging
Heating program
t
Nom.
Red. / frost.
7494f04E/0102
Forward shift
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.