D – 508 C – 07/02 D – EN pag. 35/36
Troubleshooting chart
PROBLEM
POSSIBLE CAUSES
POSSIBLE CORRECTIVE STEPS
High discharge
pressure.
1. Discharge shutoff valve partially closed.
2. Non condensable in the system.
3. Fans not running.
4. Fan control out of adjustment.
5. Heat recovery condensers dirty.
6. System overcharged with refrigerant.
7. Dirty condenser coil.
8. Air re-circulation from outlet into unit coils.
9. Air restriction in the unit.
1. Open shutoff valve.
2. Purge the non condensable from the
condenser coil after shutdown.
3. Check fan fuses and electrical circuits.
4. Check that unit set-up in Microprocessor
matches the unit model number. Check
Microprocessor condenser pressure
sensor for proper operation.
5. Clean the condenser tubes by mechanical
or chemical tools
6. Check for excessive sub-cooling. Remove
the excess charge.
7. Clean the condenser coil.
8. Remove the cause of re-circulation.
9. Remove obstructions near unit.
Low discharge
pressure
1. Wind effect at low ambient temperature.
2. Condenser fan control not correct.
3. Low suction pressure.
4. Compressor operating unloaded.
1. Protect unit against excessive wind into
vertical coils.
2. Check that unit set-up in Microprocessor
matches the unit model number.
3. See Corrective steps for low suction
pressure.
4. See Corrective steps for failure to load.
Low suction
pressure
1. Inadequate refrigerant charge quantity.
2. Evaporator dirty.
3. Clogged liquid line filter-drier.
4. Expansion valve malfunctioning.
5. Insufficient water flow to evaporator.
6. Water temperature leaving evaporator is
too low.
7. Evaporator head ring gasket slippage.
1. Check liquid line sight-glass. Check unit
for leaks.
2. Carry out chemical cleaning.
3. Replace.
4. Check expansion valve superheat and
valve opening position. Replace the valve
only if certain that the valve is not working.
5. Check water pressure drop across the
evaporator and adjust the flow.
6. Adjust water temperature to higher value.
7. Low suction pressure and low superheat
both present may indicate an internal
problem. Consult factory.
High suction
pressure
1. Excessive load - high water temperature.
2. Compressor unloaders open.
3. Superheat is too low.
1. Reduce load or add additional equipment.
2. See Corrective Steps below for failure of
compressor to load.
3. Check superheat on Microprocessor
display. Check suction line sensor
installation and the sensor itself.
Unit doesn’t
switch in Heat
Recovery
operation Mode
1. “Q7” selector switch doesn’t work.
2. No Heating load required.
3. Flow switch not operating.
4. 4-way solenoid valve not working.
5. “W10” sensor element not fixed in the well
pocket.
6. “W10” sensor element gives wrong signal.
7. “TC10” Microprocessor control doesn’t
work.
1. Replace the selector switch
2. Add additional equipment.
3. Check water pump.
4. Check the solenoid valve and if the 4-way
valve is blocked. Replace the wrong
components.
5. Fix the element in the well pocket properly.
6. Replace the element.
7. Check the supply connections or replace
them.
