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Siemens Building Technologies Basic Documentation RVL471 CE1P2524E
HVAC Products 16 Function block "Basic settings d.h.w." 23.10.2002
16.4 Frost protection for d.h.w.
The frost protection for d.h.w. provided by the RVL471 is ensured by sensors B3, B31
and B32. The behavior depends on the type of plant.
16.4.1 Frost protection in the d.h.w. storage tank
This type of frost protection is used with plant types x–1, x–2, and x–3. It always en-
sures a minimum switch-on temperature of 5 °C. If the temperature acquired with sen-
sor B31 or B32 falls below 5 °C, storage tank charging will immediately be started (in-
dependent of other settings), which generates a heat requisition to the primary control-
ler. The switch-off temperature is at 5 °C plus the switching differential (set on operating
line 128).
When using thermostats, there is no frost protection for the d.h.w. storage tank.
16.4.2 Frost protection in the d.h.w. storage tank flow
This type of frost protection is used with plant types x–2.
If the d.h.w. flow temperature (acquired with sensor B3) falls below 5 °C, the charging
pump starts to run. The mixing valve will not be opened and there will be no heat requi-
sition to the primary controller.
The switch-off temperature is 6 °C.
16.4.3 Frost protection for the secondary d.h.w. flow
With plant types x–4, no frost protection for d.h.w. can be provided since it cannot be
made certain that sensor B3 will acquire the temperature in the heat exchanger when
d.h.w. heating is switched off (circulating pump OFF).
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