Riello NXHM - General Symptoms

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13.2 General symptoms
Symptom 1: The unit is turned on but the unit is not heating or cooling as expected
POSSIBLE CAUSES CORRECTIVE ACTION
The temperature setting is not correct
Check the parameters.T4HMAX,T4HMIN in heat mode.
T4CMAX,T4CMIN in cool mode. T4DHWMAX,T4DHWMIN in DHW mode.
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• Make sure there is no air in the water system.
• Check the water pressure.
The water pressure must be >1 bar (water is cold).
• Make sure that the expansion vessel is not broken.
• Check that the resistance in the water circuit is not too high for the pump.
The water volume in the installation is too low.
Make sure that the water volume in the installation is above the minimum
required valve (refer to "9.4.2 Water volume and sizing expansion vessels").
Symptom 2: The unit is turned on but the compressor is not starting (space heating or domestic water heating)
POSSIBLE CAUSES CORRECTIVE ACTION
The unit maybe operate out of its operation range (the water
temperature is too low).
In case of low water temperature, the system utilizes the backup heater (if
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• Check that the backup heater power supply is correct.
• Check that the backup heater thermal fuse is closed.
• Check that the backup heater thermal protector is not activated.
• Check that the backup heater contactors are not broken.
Symptom 3: Pump is making noise (cavitation)
POSSIBLE CAUSES CORRECTIVE ACTION
There is air in the system. Purge air.
Water pressure at pump
inlet is too low.
• Check the water pressure.
The water pressure must be > 1 bar (water is cold).
• Check that the manometer is not broken.
• Check that the expansion vessel is not broken.
• Check that the setting of the pre- pressure of the expansion
vessel is correct (refer to "9.4.2 Water volume and sizing expansion
vessels").
Symptom 4: The water pressure relief valve opens
POSSIBLE CAUSES CORRECTIVE ACTION CORRECTIVE ACTION
The expansion vessel is broken. Replace the expansion vessel
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0.3MPa.
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0.15~0.20MPa (refer to "9.4.2 Water volume and sizing expansion vessels").
Symptom 5: The water pressure relief valve leaks
POSSIBLE CAUSES CORRECTIVE ACTION
Dirt is blocking the water pressure relief valve outlet.
Check for correct operation of the pressure relief valve by turning the red
knob on the valve counter clockwise:
• If you do not hear a clacking sound, contact your local dealer.
• In case the water keeps running out of the unit, close both the water inlet and
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Symptom 6: Space heating capacity shortage at low outdoor temperatures
Symptom 6: Space heating capacity shortage at low outdoor temperatures
POSSIBLE CAUSES CORRECTIVE ACTION
Backup heater operation is not activated.
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see "10.5.
Field settings" Check whether or not the thermal protector of the backup he-
ater has been activated (refer to "Controls parts for backup heater(IBH)").
Check if booster heater is running, the backup heater and booster heater
can’t operate simultaneously.
Too much heat pump capacity is used for heating domestic hot
water (applies only to installations with a domestic hot water
tank).
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red appropriately:
• Make sure that the "DHW PRIORITY" in the user interface is disabled.
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vate the booster heater for domestic water heating.
Symptom 6: Space heating capacity shortage at low outdoor temperatures