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Siemens Switzerland Ltd
User manual RVS61.843 CE1U2355en_02
HVAC Products 6 The settings in detail 23. November 2007
Defrosting with the fan is considered completed when one of the 2 following conditions
is satisfied:
• The temperature difference (8477) between incoming outside air (B91) and
evaporator (B84) is smaller than that set by your supplier
• When defrosting with the fan, the defrost time is reached
The defrost process at low outside temperatures takes more time than at higher outside
temperatures.
Heating mode is resumed after successful completion of the defrost process either
through process reversal or with the fan. “Duration defrost lock“, “Time up to forced
defrost“ and “Defrost settling time“ (2959 OEM) start to run again.
On completion of “Defrost settling time“ (2959 OEM), “Temp diff defrost icefree“ is
acquired and used to generate the new setpoint (8478).
When there is a heat pump lock pending, any active defrost process is completed.
Defrosting through process reversal can also be effected manually. Either via one of
the inputs EX1 – EX7 or via the operating line (7152). With manual defrosting, no
consideration is given to the release temperature (2951) and to “Duration defrost lock“
(2962).
Manual defrosting is also possible during ”Duration defrost lock” and above “Defrost
release below OT” (2951). A defrost process in progress is completed, independent of
“Defrost release below OT“.
Line no. Operating line
2951 Defrost release below OT
2958 Numb defrost attempts max
2962 Duration defrost lock
2963 Time up to forced defrost
2964 Defrost time max
2965 Dripping time evapor
The defrost function can be released only when the source inlet temperature (B91) lies
below the release temperature set here. Above this outside temperature, the automatic
defrost function is not active.
If the defrost process could not be successfully completed, another attempt is made
after a preheating phase (see “Duration defrost lock”). If, during the number of attempts
set here, it was still not possible to successfully complete the defrost process, the heat
pump is switched off and generates an error message.
For the heat pump to resume operation, the fault must be manually reset.
When the heat pump is switched on in heating mode, “Duration defrost lock” begins to
run. It is at the end of this period of time at the earliest the controller is allowed to start
the next evaporator defrost attempt.
Prerequisite for defrosting is that the source temperature (B91) lies below the set
release temperature (2951).
After a prematurely aborted defrosting attempt (see “Defrost time max“), the heating
water is preheated during the period of time “Duration defrost lock”. If an electric
immersion heater is installed in the flow or in the buffer / combi storage tank, it is
switched on to support preheating. Then, a direct change to defrost mode is made.
If the heat pump was in operation during the period of time set here, without defrosting
in the meantime, forced defrosting will take place.
The same prerequisite applies here: the source temperature (B91) must lie below the
set release temperature (2951).
Defrost end when
defrosting with the fan
Resuming heating mode
and preparing the next
defrost process
Manual defrosting
Defrost release
below OT
Numb defrost attempts
max
Duration defrost lock
Time up to forced defrost
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