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Description
Process
Notes
Siemens Building Technologies
HVAC Products
6.9.3
For the heating circuit
Frost protection for the heating circuit is active with both types of application, pump
heating circuit and mixing heating circuit. If the flow temperature of the heating circuit
(or in the case of a pump heating circuit, the temperature of the boiler) falls below 5 °C,
a valid heat demand signal of 10 °C will be generated. This causes the heating circuit
pump to be activated and – in case of the mixing heating circuit – the mixing valve ac-
tuator to be driven to the required position.
If the flow temperature reaches the switch-off threshold of 7 °C, the heat demand will
be maintained for another 5 minutes. This ensures that the hot water will reach the
entire heating circuit including the return.
6.9.4
For the d.h.w. storage tank
If the d.h.w. temperature drops significantly, the frost protection function will be acti-
vated. If a heat transfer pump (Q3 or Q11, operating line 531) has been defined and the
temperature differential required for the transfer of heat is available (operating line 534),
the transfer pump will be activated.
If no heat transfer pump has been defined, a heat demand signal is delivered to the
electric immersion heater, if fitted (ZuFu5, operating lines 146 and 172).
If there is no electric immersion heater either, the heat demand signal will be sent to a
controllable heat source (oil- or gas-fired boiler).
If...
If the actual value of the d.h.w. temperature at the coldest sen-
sor falls below the value given below...
• For oil- / gas-fired boiler (TBWx < 5 °C)
• For electric immersion heater / transfer pump: (TBWx < 7 °C)
If the actual value of the d.h.w. temperature at the coldest sen-
sor rises above the value given below...
(SDBW = d.h.w. switching differential, operating line 751
• For oil- / gas-fired boiler (TBWx > 5 °C + SDBW)
• For electric immersion heater / transfer pump: (TBWx > 10 °C)
• The frost protection setpoint for the d.h.w. is factory-set as indicated above and
cannot be changed.
• Pump overrun will be activated after d.h.w. heating is completed, if the d.h.w. was
not heated with the electric immersion heater.
• The frost protection function only acts in the case the d.h.w. storage tank is con-
nected directly to the RVA65.642. In the case of plant types with d.h.w. heating via
BMU, this function must be provided by the BMU
• The frost protection function is only active when using a temperature sensor. If the
d.h.w. is heated with the help of a control thermostat, no frost protection function is
possible because there is no actual value of the storage tank temperature
Basic Documentation RVP540 / RVP550
General control processes
then...
... the frost protection
function for the d.h.w.
becomes active
... the frost protection
function for d.h.w. will
)
be terminated
EXP
CE1P2488en
04.11.2009
331/348
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