Ariston NUOS, Manual, Page: 84 / 120

Heat pump water heater - OPERATING AND MAINTENANCE INSTRUCTIONS FOR THE USER
83
171
Pressure transducer:
decalibration
ON OFF
Replace the component
If the error persists, recover the residual gas, find the
leak in the cooling circuit and repair it, empty the cooling
circuit and recharge with 1300 grams of coolant
181
Electronic expansion valve:
KO
ON OFF
Replace the coil of the component
If the error persists, recover the residual gas and replace
the component; empty the cooling circuit and recharge
with 1300 grams of coolant
Encoding of domestic water circuit codes
210
High NTC sensor (hot water):
short circuit or open circuit
ON OFF Replace the component
220
Medium NTC sensor: short
circuit or open circuit
ON ON Replace the component
230
Low NTC sensor (heating
element zone): short circuit or
open circuit
OFF OFF Replace the component
231
Low NTC sensor (heating
element zone): safety
intervention (1st level)
OFF OFF Replace the mainboard
232
Low NTC sensor (heating
element zone): safety
intervention (2nd level)
OFF OFF Replace the mainboard
240
Impressed current anode:
short circuit
OFF OFF Replace the component
241
Impressed current anode:
open circuit
OFF OFF
Check the presence of water inside the product
If the error persists, replace the component
Encoding of electronic circuit codes
310 ON/OFF repeated OFF OFF
Wait 15 minutes before unblocking the product with the
ON/OFF button
321 Mainboard: internal fault OFF OFF Replace the component
331
Mainboard-display wiring: no
communication
OFF OFF
Replace the mainboard-display communication wiring
If the error persists, replace the mainboard and display.
8. MAINTENANCE (for authorized personnel)
WARNING! Observe the general warnings and safety instructions listed in the previous paragraphs
and strictly adhere to the indications therein contained.
All maintenance operations and interventions should be performed by qualified personnel (i.e. with the
necessary requirements as outlined in the applicable norms in force).
After routine or extraordinary maintenance, we recommend filling the appliance's tank with water and draining it
completely to remove any residual impurities.
8.1 Draining the appliance
The appliance must be drained if left inactive in a room subject to frost.
When necessary, empty the appliance as follows:
-
Permanently disconnect the appliance form the mains electricity.
-
Close the shut-off valve, if installed, or the central tap of the domestic water supply network.
-
Open the hot water tap (washbasin or bathtub).
-
Open the cock on the safety device (in countries which acknowledge EN 1487) or the special cock installed on
the "T" fitting, as described in paragraph 4.4.