Nibe S2125, Installer Manual, Page: 33 / 64

Control conditions
CONTROL CONDITIONS DEFROSTING
• If the temperature of the evaporator sensor (BT16) is below
the start temperature for the defrosting function, S2125
counts the time to "active defrosting" for each minute
that the compressor is running, to create a defrosting re-
quirement.
• 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 require-
ment has been fulfilled, at the same time as there is a de-
frosting requirement and the outdoor temperature
(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 start earlier than the normal defrosting. If
the safety defrosting occurs ten times in a row, the
evaporator (EP1) on S2125 must be checked, which is in-
dicated by an alarm.
• If "de-icing fan" is activated in the indoor module/control
module, "de-icing fan" starts at the next "active defrost-
ing". "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 return
temperature alarm is blocked for two minutes after de-
frosting.
Passive defrosting:
1. If there is no compressor demand, passive defrosting
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 return
temperature alarm is blocked for two minutes after de-
frosting.
33 Chapter 7 | Control NIBE S2125