Control conditions
CONTROL CONDITIONS DEFROSTING
• If the temperature on the evaporation sensor (BT16)
is below the start temperature for the defrosting
function, F2120 counts the time to "active defrosting"
each minute that the compressor is running, to create
a defrosting requirement.
• Time until "active defrosting" is shown in minutes on
the indoor module / control module. Defrosting starts
when this value is 0 minutes.
• "Passive defrosting" is started, if the compressor re-
quirement has been fulfilled, at the same time as there
is a defrosting requirement and the outdoor temperat-
ure (BT28)is greater than 4 °C.
• Defrosting occurs actively (with compressor on and
fan off) or passively (with compressor off and fan on).
• If the evaporator is too cold, a "safety defrost" starts.
This defrosting can be started earlier than the normal
defrosting. If there are ten safety defrostings in a row
the evaporator (EP1) on F2120 must be checked,
which is indicated by alarm 341.
• If "de-icing fan" is activated in menu 5.11.1.1, "de-icing
fan" starts at the next "active defrosting". "De-icing fan"
removes the build-up of ice on the fan blades and the
front fan grille.
Active defrosting:
1.
The four way valve shifts to defrosting.
2.
The fan stops and the compressor continues to run.
3.
When defrosting is complete, the four-way valve
switches back to heating operation. The compressor
speed is locked for a short period.
4.
The ambient temperature is locked and the high re-
turn temperature alarm is blocked for two minutes
after defrosting.
Passive defrosting:
1.
If there is no compressor demand, passive defrost-
ing can start.
2.
The four way valve does not shift.
3.
Fan runs at high speed.
4.
If there is a compressor demand, passive defrosting
stops and the compressor starts.
5.
When passive defrosting is complete, the fan stops.
6.
The ambient temperature is locked and the high re-
turn temperature alarm is blocked for two minutes
after defrosting.
There are several possible reasons for an active
defrosting to end:
1.
If the temperature of the evaporator sensor has
reached its stop value (normal stop).
2.
When defrosting has gone on for longer than 15
minutes. This may be due to too little energy in the
heat source, too strong a wind effect on the evapor-
ator and/or that the sensor on the evaporator is not
correct and therefore displays too low a temperature
(at cold outdoor air).
3.
When the temperature on the return line sensor,
BT3, falls below 10 °C.
4.
If the temperature of the evaporator (BP8) falls be-
low its lowest permitted value. After ten unsuccess-
ful defrostings, F2120 must be checked. This is in-
dicated as an alarm 228.
37Chapter 7 | Control - IntroductionNIBE F2120
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