Ideal
The Ideal Logic Heat 12 is a 12 kW wall-hung regular gas boiler with 89.4% seasonal efficiency, introduced in 2014. It features an aluminium heat exchanger and operates with a 4.8-12 kW modulation range.
The Ideal Logic Heat 12 is a wall-hung, condensing regular boiler designed for natural gas central heating systems. Introduced in 2014, this 12 kW model (GC number 41-399-99) is part of Ideal's Logic Heat family, manufactured in the UK and Ireland. It provides a maximum central heating output of 12 kW, making it suitable for various domestic installations requiring a system boiler. This page offers technical specifications, fault code diagnostics, and installation details for heating engineers and homeowners.
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Full technical specifications extracted from the manufacturer brochure. Empty sections are hidden.
Pipework from the boiler is routed upwards.
Ideal stelrad group recommend Water Treatment in accordance with the Benchmark Guidance Notes on Water Treatment in Central Heating Systems. If water treatment is used Ideal stelrad group recommend only the use of Scalemaster Gold 100, FERNOX, MB-1, ADEy MC1 or SENTINEL-X100 inhibitors and associated water treatment products, which must be used in accordance with the manufacturers' instructions.
The Ideal Logic Heat 12 delivers a nominal heat output of 12 kW, with a modulation range from 4.8 kW to 12 kW, ensuring efficient operation across varying demand. Its seasonal efficiency is rated at 89.4%, classifying it as a high-efficiency condensing appliance. The boiler operates at a natural gas inlet pressure of 20 mbar and has a maximum gas rate of 1.246 m³/h.
Physically, the unit measures 700mm high, 395mm wide, and 278mm deep, with a dry weight of 23 kg, facilitating compact installation. Key connections include 22mm flow and return pipes, a 15mm gas pipe, and a 21.5mm condensate drain. The primary heat exchanger is constructed from aluminium. The Logic Heat 12 is compatible with standard heating controls, including thermostatic radiator valves and room thermostats, and features weather compensation capabilities. Safety features include frost protection, a safety valve, and overheat protection.
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/ideal/logic-heat-18#fault-c 0 to jump straight to the entry.
| Code | Meaning | Details |
|---|---|---|
| C 0 | BCC Activation Fault Show causes & actionsUser action Reset the appliance - if the boiler fails to operate then please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII). Engineer action Reset the appliance - if the boiler fails to operate then please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII). | Details |
| C 2 | BCC Fault Show causes & actionsUser action Reset the appliance - if the boiler fails to operate then please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII). Engineer action Reset the appliance - if the boiler fails to operate then please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII). | Details |
| F 0 | Unconfigured PCB | — |
| F 2 | Flame Loss Show causes & actionsEngineer action See Action - Fault Code L 2 | Details |
| F 3 | Fan Fault Show causes & actionsUser action Reset the appliance - if the boiler fails to operate then please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII). Engineer action Reset the appliance - if the boiler fails to operate then please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII). | Details |
| F 4 | Flow Thermistor Show causes & actionsUser action Reset the appliance - if the boiler fails to operate then please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII). Engineer action Reset the appliance - if the boiler fails to operate then please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII). | Details |
| F 5 | Return Thermistor Show causes & actionsUser action Reset the appliance - if the boiler fails to operate then please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII). Engineer action Reset the appliance - if the boiler fails to operate then please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII). | Details |
| F 6 | Outside Sensor Failure Show causes & actionsUser action Reset the appliance - if the boiler fails to operate then please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII). Engineer action Reset the appliance - if the boiler fails to operate then please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII). | Details |
| F 7 | Low Mains Voltage Show causes & actionsUser action Contact a qualified electrician or your electricity provider. Engineer action Contact a qualified electrician or your electricity provider. | Details |
| F 9 | PCB Fault Show causes & actionsUser action Please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII). Engineer action Please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII). | Details |
| F A | Flow/Return Reversed Show causes & actionsUser action Please contact a Gas Safe Registered Engineer. In IE contact a Registered Gas Installer (RGII). Engineer action Please contact a Gas Safe Registered Engineer. In IE contact a Registered Gas Installer (RGII). | Details |
| F d | No Water Flow Show causes & actionsUser action Please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII). Engineer action Please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII). | Details |
| L 1Lockout | Flow Temperature Overheat or Unconfigured PCB Show causes & actionsUser action Check system pressure is between 1 & 1.5bar on the pressure gauge. If the boiler fails to operate then please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII). Engineer action Check system pressure is between 1 & 1.5bar on the pressure gauge. If the boiler fails to operate then please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII). | Details |
| L 2Lockout | Ignition Lockout Show causes & actionsUser action 1. Check other gas appliances in the house are working to confirm a supply is present in the property. 2. If other appliances do not work or there are no other appliances, check the gas supply is on at the meter and/or pre payment meter has credit. If the boiler fails to operate then please contact Ideal (if under warranty) or alternatively a Gas Safe Registered engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII). Engineer action 1. Check other gas appliances in the house are working to confirm a supply is present in the property. 2. If other appliances do not work or there are no other appliances, check the gas supply is on at the meter and/or pre payment meter has credit. If the boiler fails to operate then please contact Ideal (if under warranty) or alternatively a Gas Safe Registered engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII). | Details |
| L 5Lockout | 5 Boiler Resets in 15 minutes Show causes & actionsUser action 1. Turn power off and on at the fused spur. 2. If the boiler fails to operate please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII). Engineer action 1. Turn power off and on at the fused spur. 2. If the boiler fails to operate please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII). | Details |
| L 6Lockout | False Flame Lockout Show causes & actionsUser action Reset the appliance - if the boiler fails to operate then please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII). Engineer action Reset the appliance - if the boiler fails to operate then please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII). | Details |
Patterns that group across the manufacturer's fault-code table. Each entry links to the full code listing further down the page.
User: Check system pressure is between 1 & 1.5bar on the pressure gauge. If the boiler fails to operate then please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII).
Engineer: Check system pressure is between 1 & 1.5bar on the pressure gauge. If the boiler fails to operate then please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII).
Triggered by fault code L 1.
User: 1. Check other gas appliances in the house are working to confirm a supply is present in the property. 2. If other appliances do not work or there are no other appliances, check the gas supply is on at the meter and/or pre payment meter has credit. If the boiler fails to operate then please contact Ideal (if under warranty) or alternatively a Gas Safe Registered engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII).
Engineer: 1. Check other gas appliances in the house are working to confirm a supply is present in the property. 2. If other appliances do not work or there are no other appliances, check the gas supply is on at the meter and/or pre payment meter has credit. If the boiler fails to operate then please contact Ideal (if under warranty) or alternatively a Gas Safe Registered engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII).
Triggered by fault code L 2.
User: 1. Turn power off and on at the fused spur. 2. If the boiler fails to operate please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII).
Engineer: 1. Turn power off and on at the fused spur. 2. If the boiler fails to operate please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII).
Triggered by fault code L 5.
User: Reset the appliance - if the boiler fails to operate then please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII).
Engineer: Reset the appliance - if the boiler fails to operate then please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII).
Triggered by fault code L 6.
User: Reset the appliance - if the boiler fails to operate then please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII).
Engineer: Reset the appliance - if the boiler fails to operate then please contact Ideal (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period. In IE contact a Registered Gas Installer (RGII).
Triggered by fault code C 0.
Diagnostic checklists from engineer-submitted Ideal faults, with step-by-step checks and safety notes.
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Common questions from engineers and homeowners about the Ideal Logic Heat 18.
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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.