Fujitsu WATERSTAGE 112 Maintenance Document page 61

Heat Pump, Split System, Single Service, 3 phase
Outdoor unit does not defrost
•
Is condensation
(outdoor unit directly on the ground)?
•
Are the auxiliaries powered?
•
In boiler backup mode, is the boiler authorized?
•
In very cold areas, a fusing resistance value is
recommended.
Is the installation regularly subject to micro-
outages of power (frequent outages on the mains
power system may
problems)?
Is there a peak day clearing (EJP) outage on the
installation?
•
Does the heat pump regularly switch to high
pressure safety mode?
If this occurs at low temperatures (< 5 °C), we
recommend checking that the water pump is
operating properly.
Note:
Outdoor unit defrosting is controlled by the exchanger sensor and the controller board. If no frosting is observed
and no anomaly is otherwise noted, the sensor and board must be inspected and the faulty part will have to be
replaced.
Defrosting
a. Defrost beginning conditions
17' < t < 62'
O Exch T
≤ -9°C
OT – O Exch T >5°C
O Exch T : outdoor unit exchanger temperature
OT : outdoor temperature
t : Cumulative compressor operating time
Maintenance Document 1394-1
drain properly discharged
also cause defrosting
Start of heat mode
(Compressor ON)
(No defrost for 10 min)
st
1 defrost
Cumulative compressor operating time
62' < t < 240'
O Exch T O Exch T
≤ -5°C
•
Is the
temperature/pressure curve)?
Insufficient charging will result in frequent icing.
Overcharging will result in frequently switching to
HP safety mode.
(If you still have doubts as to the charge, perform the
charging with an electronic scale).
•
Outdoor unit defrosting is controlled by the
exchanger sensor and the controller board.
If the defrost sensor is not iced up while the rest of
the exchanger is, then:
⇒ Move the sensor between the exchanger blades
to a place where the exchanger is iced up.
⇒ If all these points have been checked, replace the
outdoor controller board.
Subsequent defrosts
240' < t 35' < t < 240'
≤ -3°C
Defrost
charge correct (refer
240' < t
O Exch T O Exch T
≤ -10°C ≤ -3°C
to the
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