Ariston
CLAS Net ONE 24
Combi Boiler
24kW
2020-present
ErP A
46 fault codes
<p>The CLAS Net ONE 24 is a combi boiler from Ariston, available at 24kW output. Produced 2020-present.</p>
CLAS Net ONE 24 Fault Codes 46
Code
Description
Severity
Type
101
Overheat — Safety Thermostat Triggered
The boiler has overheated and the safety thermostat has shut it down. Usually caused by poor…
High
Engineer
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102
Pressure Sensor Error (E-Combi Evo)
On Ariston E-Combi Evo boilers, code 102 indicates a pressure sensor fault.
Medium
Engineer
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103
Insufficient Water Circulation
The boiler is not detecting adequate water circulation through the primary heating circuit. Usually caused by…
Medium
Engineer
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104
Insufficient Circulation / Pump Fault
The pump is not providing adequate water circulation. The temperature rise is too fast, indicating restricted…
High
Engineer
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105
Insufficient Circulation on DHW Circuit
The domestic hot water circuit has poor circulation. The flow rate through the plate heat exchanger…
Medium
Engineer
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106
Low Water Pressure
System water pressure has dropped below the safe operating level. The boiler cannot operate without adequate…
Low
DIY
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107
Low Water Pressure with No Reset
System pressure is critically low and the boiler has locked out. Unlike code 106, this will…
Medium
DIY
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108
Insufficient Water — Refill Required
On Ariston combi boilers, code 108 indicates the system has insufficient water and needs to be…
Low
DIY
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109
System Pressure Too High (Clas Net One)
On Ariston Clas Net One boilers, code 109 indicates system pressure has exceeded 3 bar.
Medium
Engineer
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110
CH Flow Temperature Sensor Fault
The central heating flow temperature sensor (probe) has an open circuit or short circuit fault.
Medium
Engineer
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112
CH Return Temperature Sensor Fault
The central heating return temperature sensor has an open circuit or short circuit fault.
Medium
Engineer
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118
Flame Detected After Shutdown
Flame signal present when gas valve should be closed.
High
Engineer
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120
Flow/Return Sensors Reversed
The sensors are fitted to the wrong pipes.
Medium
Engineer
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201
Flow Temperature Sensor Fault
The flow NTC temperature sensor has an open circuit or short circuit. The boiler cannot monitor…
Medium
Engineer
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202
DHW Temperature Sensor Fault
The domestic hot water NTC temperature sensor has developed a fault. The boiler cannot accurately monitor…
Medium
Engineer
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203
Return Temperature Sensor Fault
The return NTC temperature sensor has an open circuit or is giving incorrect readings.
Medium
Engineer
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301
EEPROM Error — PCB Fault
There is an EEPROM (memory chip) fault on the main PCB. The boiler cannot read or…
High
Engineer
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302
Communication Error — PCB
A communication error has occurred on the main PCB, possibly between the PCB and display or…
Medium
Engineer
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303
Main PCB Error
The main Printed Circuit Board has detected an internal error.
High
Engineer
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304
Too Many Resets — 5 in 15 Minutes
The boiler has been reset 5 or more times within 15 minutes and has entered a…
Medium
DIY
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305
PCB / EEPROM Error
The printed circuit board has an internal memory error. The boiler's configuration data may be corrupted.
High
Engineer
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306
Air Pressure Switch Fault
The air pressure switch is not closing when the fan runs. The boiler cannot verify adequate…
High
Engineer
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501
No Flame Detected / Ignition Failure
The most common Ariston fault code. The burner has failed to ignite or the ionisation signal…
Medium
DIY
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502
Flame Detected With Gas Valve Closed
The boiler's ionisation circuit is detecting a flame when the gas valve should be completely closed.…
High
Engineer
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504
Flame Lift
The boiler has detected 'flame lift' — the flame has lifted away from the burner surface,…
High
Engineer
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5P1
First Ignition Failed (Warning)
The first ignition attempt failed — the boiler will try again. This is a warning (non-lockout)…
Low
DIY
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5P2
Second Ignition Failed (Warning)
The second ignition attempt has also failed. The boiler may escalate to a 501 lockout.
Medium
DIY
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601
Fan Fault
The fan is not starting, running too slowly, or has stopped unexpectedly. The boiler cannot safely…
High
Engineer
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604
Insufficient Fan Speed
The boiler fan is not reaching the required speed for safe combustion — preventing ignition.
High
Engineer
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607
Gas Valve Relay Fault
The gas valve relay on the PCB is not operating correctly. The boiler cannot safely control…
High
Engineer
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610
Thermal Fuse Open
The thermal fuse (a one-time safety device) has activated due to extreme overheating. Once blown, it…
High
Engineer
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612
Fan Speed Incorrect Measurement
The fan speed sensor is giving an incorrect reading — fan speed cannot be confirmed as…
High
Engineer
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