Fujitsu WATERSTAGE WOYG160LJL Maintenance Document page 46

Outdoor unit does not defrost
Is condensation drain properly discharged
(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 also cause defrosting
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),
werecommend 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
- 46 -
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 charge correct
(refer to the temperature/pressure curve) ?
- Insuffi cient 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
240' < t
O Exch T O Exch T
-10°C -3°C
Waterstage / Maintenance Manual / 2105 - EN