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Siemens Switzerland Ltd
User manual RVS61.843 CE1U2355en_02
HVAC Products 6 The settings in detail 23. November 2007
This defines the behavior of the heat pump in the case of forced buffer storage tank
charging.
Locked
The heat pump is not put into operation for forced buffer storage tank charging.
Released
The heat pump can be put into operation for forced buffer storage tank charging.
This defines the behavior of the heat pump in the case of full buffer storage tank
charging.
Off
The heat pump remains locked until the buffer storage tank is fully charged by some
other heat source. It is released only when there is not enough heat for satisfying the
current demand (4720).
On
The heat pump is released when the buffer storage tank is fully charged.
Defrost function for air-to-water HP
Defrosting of an iced-up evaporator is effected either with the fan or the compressor by
reversing the process – independent of the outside temperature:
• Above the set outside temperature with the fan
• Below the set outside temperature by reversing the process
The example below shows a heat pump in heating mode and in defrosting mode with
process reversal.
Plant in heating mode
In normal heating mode of an air-to-water heat pump, condensation can occur at low
temperatures, causing the evaporator to ice up. This reduces the heat pump’s output
and can lead to low-pressure malfunctions or damage to the evaporator.
B21
B71
Q9
B91
T
T
T
K19
B84
T
K1
Y22
E17
Gas low-pressure
Gas high-pressure
Liquid
Plant in defrost mode (process reversal)
The evaporator is defrosted either with the fan or – as shown in the example below –
with process reversing valve Y22. For process reversal, a HP partial diagram with
process reversing valve (Y22) must be used.
Demand-dependent defrost control ensures that the defrost energy drawn from the
heating circuit in the case of process reversal will be kept at a minimum. During the
defrost process with process reversal, the fan remains deactivated.
For forced buffer storage
tank charging
Full charging of buffer
storage tank
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