Ariston
The Ariston CLAS NET One 24 is a 24 kW condensing combi boiler with 94% seasonal efficiency, an A-rated ErP for heating and DHW, and a 12-year warranty.
The Ariston CLAS NET One 24 is a natural gas and LPG compatible condensing combi boiler designed for wall-hung installation in UK domestic properties. This appliance provides both central heating and domestic hot water, making it suitable for various residential applications. This page details technical specifications, performance data, installation requirements, and common fault codes, serving as a reference for heating engineers and homeowners researching the model.
Stick a QR tag on the case, scan it on every service and give your customer a permanent, shareable service history they can pull up from any phone.
Permanent, shareable service history
One QR scan on the boiler surfaces every previous fault, part change and visit — no paperwork to dig out.
Free AI fault diagnostics, built in
Every tag you fit unlocks the AI diagnostic tool for that exact model — paste a fault code, get a ranked cause list.
Your name on the boiler forever
When the next service or breakdown comes around the homeowner scans and sees your number first.
First 12 BoilerTags are free
Tag every install and service you do from now on — the subscription only kicks in once you scale past your first dozen.
Diagnosing a fault on a Ariston CLAS SYSTEM ONE 24 right now?
Try the free AI fault diagnostics tool — no signup needed.
Full technical specifications extracted from the manufacturer brochure. Empty sections are hidden.
A: Central Heating Flow, B: Domestic Hot Water Outlet, C: Gas Inlet, D: Domestic Cold Water Inlet, E: Central Heating Return
BS 7593
The Ariston CLAS NET One 24 is a wall-hung condensing combi boiler, offering a maximum central heating output of 21.4 kW and a domestic hot water output of 24.9 kW. It operates with a seasonal efficiency of 94% and holds an A-rating for both heating and domestic hot water under the ErP directive, with an XL DHW profile. The boiler delivers a domestic hot water flow rate of 12.1 litres per minute at a 30°C temperature rise, supported by a preheat feature for user convenience. Its primary heat exchanger is constructed from stainless steel, contributing to durability. The appliance features a modulating pump and is designed for compatibility with natural gas and LPG, with specific inlet pressures of 20 mbar and 37 mbar respectively. Installation requires clearances of 450mm front, 50mm sides, 350mm top, and 300mm bottom, and includes a 12-year standard warranty upon registration.
Every fault code listed in the manufacturer brochure, with likely causes and engineer actions. Each code has a permalink — paste a URL like https://www.boilertag.com/boilers/ariston/clas-system-one-24#fault-101 to jump straight to the entry.
| Code | Meaning | Details |
|---|---|---|
| 101 | Overheat | — |
| 103 | — | |
| 104 | — | |
| 105 | Insufficient circulation | — |
| 106 | — | |
| 107 | — | |
| 108 | Insufficient water (request filling) Show causes & actionsShut-off due to insufficient water pressure inside the heating circuit. User action Increase the pressure by filling the heating circuit. If re-balancing is frequent, switch off the boiler, turn the external electric switch to OFF, shut off the gas cock and contact a qualified technician to check for any leaks of water. Engineer action Check for leaks of water. | Details |
| 109 | System pressure > 3 bar | — |
| 110 | C.H. Flow temp. probe circuit open / short circuit | — |
| 112 | C.H. Return temp. probe circuit open / short circuit | — |
| 114 | External sensor circuit open / short circuit | — |
| 116 | Floor Thermostat contact open | — |
| 118 | Heating delivery probe problem | — |
| 1P1 | Show causes & actionsFIRST IGNITION ATTEMPT UNSUCCESSFUL | Details |
| 1P2 | Insufficient circulation indication | — |
| 1P3 | — | |
| 1P4 | — | |
| 205 | DHW In Probe Open Circuit (Solare temp. probe) | — |
| 301 | EEPROM error | — |
| 302 | Comunication error | — |
| 303 | Main P.C.B. error | — |
| 304 | Too many (> 5) resets in 15 minutes | — |
| 305 | Main P.C.B. error | — |
| 306 | Main P.C.B. error | — |
| 307 | Main P.C.B. error | — |
| 3P9 | Sched.Maintanace-Call Service | — |
| 411 | Room sensor circuit open or short circuit Zone 1 | — |
| 412 | Room sensor circuit open or short circuit Zone 2 | — |
| 413 | Room sensor circuit open or short circuit Zone 3 | — |
| 501Lockout | No flame detected Show causes & actionsReset procedure Press the Reset button on the control panel. | Details |
| 502 | Flame detected with gas valve closed | — |
| 504 | Flame lift | — |
| 5P1 | 1st Ignition Failed | — |
| 5P2 | 2nd Ignition Failed | — |
| 5P3 | Flame cut-off | — |
| 610 | Overheat (Main heat exchanger) | — |
| 612 | Insufficient fan speed | — |
| 701 | Zone 1 send sensor defective | — |
| 702 | Zone 2 send sensor defective | — |
| 703 | Zone 3 send sensor defective | — |
| 711 | Zone 1 return sensor defective | — |
| 712 | Zone 2 return sensor defective | — |
| 713 | Zone 3 return sensor defective | — |
| 722 | Zone 2 overheating | — |
| 723 | Zone 3 overheating | — |
| 750 | All Heating Zones locked | — |
Patterns that group across the manufacturer's fault-code table. Each entry links to the full code listing further down the page.
Triggered by fault code 501.
Triggered by fault code 101.
Triggered by fault code 105.
User: Increase the pressure by filling the heating circuit. If re-balancing is frequent, switch off the boiler, turn the external electric switch to OFF, shut off the gas cock and contact a qualified technician to check for any leaks of water.
Engineer: Check for leaks of water.
Triggered by fault code 108.
Triggered by fault code 109.
Common questions from engineers and homeowners about the Ariston CLAS SYSTEM ONE 24.
We hold the Ariston CLAS SYSTEM ONE 24 manual — and every other UK boiler and heat pump brochure. Sign up and pull any model up from your phone, on the job.
Sign up to access brochuresTag it before you leave. Next scan shows every service, fault and part change — and the AI diagnostic tool is free on every tag you fit.
Specifications on this page are extracted from the manufacturer brochure. Always cross-check against the latest datasheet before commissioning or quoting. Last updated 28 June 2026.