Siemens LMU54 Series Basic Documentation page 99

Full charging of the
stratification storage tank
Recharging of the
stratification storage tank
Siemens Building Technologies
HVAC Products
With full charging, the temperature of the entire storage tank is raised to the setpoint
temperature while the pump is running at low speed. When the temperature at the upper
sensor for «TbwIst1» is too high (> TbwSmax), the demand for heat will be stopped.
Demand for DHW is stopped when, at the sensors for «TbwIst2» and «TbwIst1»:
TbwIst2 < DHW setpoint – SdBwEin2
and
TbwIst1 < TbwSmax – SdBwEin1
Demand for DHW is stopped when, at the sensor for «TbwIst2» or «TbwIst1»:
TbwIst2 > DHW setpoint + SdBwAus2Max
or
TbwIst1 > TbwSmax + SdBwAus1Max
During full charging, the charging pump runs at low speed.
This speed can be adjusted independently of heating operation, which means that it has
its own parameter «NqmodMinBw».
The burner is put into operation when TkIst < (TkSoll – SdHzEin1) (TkSoll =
TbwSoll + TuebBw).
The output demand on the burner will be adjusted between «LmodTL» and «LmodVL»
or, with active speed limitation, between «N_TL» and «N_VL».
If, during active full charging, the release criterion for full charging becomes obsolete,
the demand for DHW will be stopped based on the criteria of recharging.
With recharging, it is only the upper part of the storage tank that is brought to the
setpoint temperature while the pump runs at full speed.
Function «Recharging of the stratification storage tank» will be activated when the
conditions for full charging are not satisfied or when, in full charging mode, the sensor
for «TbwIst2» is faulty.
The evaluation for DHW demand is made only based on the sensor for «TbwIst1».
Demand for DHW is stopped when, at the sensor for «TbwIst1»:
TbwIst1 < BwSoll – SdBwEin1
Demand for DHW is stopped when, at the sensor for «TbwIst1»:
TbwIst1 > BwSoll + SdBwAus1Max
In the case of DHW demand or pump overrun, the modulating pump runs at maximum
speed or with the minimum degree of modulation.
QmodMin: Minimum degree of modulation, that is, maximum pump speed
The burner is put into operation when «TkIst < (TkSoll – SdHzEin1)» (TkSoll =
TbwSoll + TuebBw).
The output demand on the burner will be adjusted between «LmodTL» and «LmodVL»
or, with active speed limitation, between «N_TL» and «N_VL».
If, during active recharging, the release criterion for recharging becomes obsolete, the
demand for DHW will be stopped based on the criteria of full charging.
Basic Documentation LMU54... / LMU64...
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CC1P7494en
07.11.2002