55
LOW PRESSURE SHUTDOWN - HEATING
LOW PRESSURE ALARM
Operation of outdoor unit
normal?
Check operation of outdoor
unit ( 1 )
Filter dryer working
correctly ?
Refrigerant charge correct ?
Suction line valve completel
open ?
Suction temperature and/or
pressure correct ?
Unit operates correctly
Check working conditions
of outdoor unit ( 2 )
Check connecting pipes
( 3 )
Control
subcooling/subheating (5)
Check and open if
necessary
Check operation of indoor
unit ( 6 )
Control
∆
t around filter
( 4 )
NO
NO
NO
NO
SI
SI
SI
SI
SI
NO
Note:
1) Check that there is sufficient airflow, with an outdoor air temperature below 10°C the fan speed must be at its maximum
(output voltage of fan card 220V).
Check that the defrost completely melts all ice, if not the accumulation of ice on the coil can cause a reduction of heat
exchange which is necessary for a correct operation of the unit. Also check that the melt water from the defrost is adequately
drained.
2) Check that the outdoor air temperature/humidity are within the project conditions. Check that the same air is not recirculating
or for air stratification if the unit is installed below ground level.
3) Check that the length and diameter of the pipes are correcrt (see the REFRIGERANT PIPES manual). If not this could cause
excessive pressure drops and not allow the unit to operate correctly.
4) Using a contact thermometer control the temperature before and after the filter dryer (the two-way type). If the temperature
difference is over 1°C this indicates the filter is no longer effective or undersized filter and should be changed in both cases.
5) See the STARTUP manual for the check procedure.
6) If the condensing pressure is below 1200Kpa guage pressure this may cause an irregular supply to the expansion device
which would give too low a suction pressure.
Check that the airflow of the indoor unit is in order.
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