Ideal
The Ideal Logic MAX Combi C24 is a 24 kW natural gas combi boiler, introduced in 2019, offering 94% seasonal efficiency and a 9.9 lpm DHW flow rate.
The Ideal Logic MAX Combi C24 is a wall-hung natural gas condensing combi boiler, introduced in 2019. Designed for domestic heating and hot water, this model delivers a maximum central heating output of 24.2 kW and a domestic hot water flow rate of 9.9 litres per minute at a 35°C temperature rise. It is engineered for efficiency and reliability in UK residential applications, providing an ErP A-rating for both heating and hot water.
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Full technical specifications extracted from the manufacturer brochure. Empty sections are hidden.
Pipework from the boiler is routed downwards.
Water treatment in accordance with Benchmark Guidance Notes on Water Treatment in Central Heating Systems. Use SCALEMASTER SM-1 PRO, FERNOX, MBI, ADEY MC1, SENTINEL X100 or CALMAG CM100 inhibitors. Not permitted to use artificially softened water.
The Logic MAX Combi C24 operates with a central heating output range of 4.8 kW to 24.2 kW, ensuring modulated performance for varying demand. Its condensing technology contributes to a seasonal efficiency of 94% and an ErP A-rating for both heating and domestic hot water. For DHW, it provides a flow rate of 9.9 litres per minute at a 35°C temperature rise, supported by a preheat feature. The appliance weighs 36.5 kg dry and has compact dimensions, measuring 700mm high, 395mm wide, and 278mm deep, facilitating installation in typical UK properties. Flue options include horizontal, vertical, and concentric configurations, with a maximum horizontal length of 9 metres. Installation requires adherence to water quality guidelines, prohibiting artificially softened water, and ensuring appropriate clearances.
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-max-combi-c35#fault-overheat lockout 1/4 to jump straight to the entry.
| Code | Meaning | Details |
|---|---|---|
| Overheat Lockout 1/4Lockout | With Boiler Off & System Cold Show causes & actionsBoiler and CH System not filled with water or isolation, system filter and radiator valves not open. Likely causes
User action Fill system to 1.0 Bar Engineer action Fill and vent the system and open all isolation valves, then restart boiler Reset procedure RESTART PROCEDURE: TO RESTART BOILER PRESS THE RESTART BUTTON. | Details |
| Overheat Lockout 2/4Lockout | Bleed Radiators Show causes & actionsOverheat lockout due to air in radiators. Likely causes
User action Refill System to 1.0 Bar Engineer action Bleed Radiators Refill System to 1.0 Bar Restart Reset procedure RESTART PROCEDURE: TO RESTART BOILER PRESS THE RESTART BUTTON. | Details |
| Overheat Lockout 3/4Lockout | Check Radiator Valves And Boiler Valves Are Open Show causes & actionsOverheat lockout due to closed radiator or boiler valves. Likely causes
User action Restart Engineer action Check Radiator Valves And Boiler Valves Are Open Restart Reset procedure RESTART PROCEDURE: TO RESTART BOILER PRESS THE RESTART BUTTON. | Details |
| Overheat Lockout 4/4Lockout | Restart Boiler Show causes & actionsOverheat lockout persists after initial checks. Likely causes
User action Restart Boiler Engineer action If Fault Persists Contact Installer Reset procedure RESTART PROCEDURE: TO RESTART BOILER PRESS THE RESTART BUTTON. | Details |
| Ignition Lockout 1/2Lockout | Check Other Gas Appliances Work Show causes & actionsBoiler fails to ignite after a short time and then extinguishes. Likely causes
User action Check Other Gas Appliances Work Restart Boiler Engineer action Check gas supply and rectify fault Reset procedure RESTART PROCEDURE: TO RESTART BOILER PRESS THE RESTART BUTTON. | Details |
| Ignition Lockout 2/2Lockout | Check Other Gas Appliances Work Show causes & actionsBoiler fails to ignite after a short time and then extinguishes. Likely causes
User action Check Other Gas Appliances Work Restart Boiler Engineer action Check gas supply and rectify fault Reset procedure RESTART PROCEDURE: TO RESTART BOILER PRESS THE RESTART BUTTON. | Details |
| Too Many RestartsLockout | 5 restarts within 15 minutes Show causes & actionsBoiler has attempted to restart 5 times within 15 minutes. Likely causes
User action Turn power off and on Engineer action Contact Installer Reset procedure RESTART PROCEDURE: TO RESTART BOILER PRESS THE RESTART BUTTON. | Details |
| Flame On Before Gas On | Flame On Before Gas On Show causes & actionsFlame detected before gas valve opens. Likely causes
User action Restart Engineer action Check routing and integrity of internal boiler wiring is OK. Check condition of Flame Sense Electrode and replace if deteriorated. Reset procedure RESTART PROCEDURE: TO RESTART BOILER PRESS THE RESTART BUTTON. | Details |
| Water Pressure 1/3 | With Boiler Off & System Cold Show causes & actionsLow water pressure in the boiler and CH system. Likely causes
User action Fill system to 1.0 Bar Engineer action Fill and vent the system and open all isolation valves | Details |
| Water Pressure 2/3 | Bleed Radiators Show causes & actionsLow water pressure due to air in radiators. Likely causes
User action Refill System to 1.0 Bar Engineer action Bleed Radiators Refill System to 1.0 Bar | Details |
| Water Pressure 3/3 | If fault persists Show causes & actionsLow water pressure persists after initial checks. Likely causes
User action Contact Installer Engineer action Contact Installer | Details |
| Flame Loss | Flame Loss Show causes & actionsBoiler ignites for a short time and then extinguishes. Likely causes
User action Restart Engineer action Check the detection electrode and associated harness for: continuity, visual condition and position. Check if condensate pipe is blocked. Check if flue is blocked. Replace as necessary. Is the Gas Pressure available at the Boiler Inlet (>18 mbar)? Is 24Vdc supply available at the Gas Valve while the flame is on? Check spark generator and associated harness for: continuity and visual condition. Are these functioning correctly? Check ignition electrode and associated harness for: continuity, visual condition and position. Are these functioning correctly? Check siphon and condensate drain pipe work for blockage and rectify if necessary. Boiler now working OK? Reset procedure RESTART PROCEDURE: TO RESTART BOILER PRESS THE RESTART BUTTON. | Details |
| Fan Fault | Fan Fault Show causes & actionsIssue with fan wiring or operation. Likely causes
User action Restart Engineer action Rectify Wiring & connections Replace PCB Replace Fan Reset procedure RESTART PROCEDURE: TO RESTART BOILER PRESS THE RESTART BUTTON. | Details |
| Flow Thermistor Fault | Flow Thermistor Fault Show causes & actionsIssue with flow thermistor wiring or value. Likely causes
User action Restart Engineer action Securely connect the wiring to the Flow Thermistor Fit a new Thermistor Securely connect the wiring to the PCB Replace PCB Reset procedure RESTART PROCEDURE: TO RESTART BOILER PRESS THE RESTART BUTTON. | Details |
| Return Thermistor Fault | Return Thermistor Fault Show causes & actionsIssue with return thermistor wiring or value. Likely causes
User action Restart Engineer action Fit a new Thermistor Check and replace wiring as necessary Replace PCB Reset procedure RESTART PROCEDURE: TO RESTART BOILER PRESS THE RESTART BUTTON. | Details |
| Outside Sensor Fault | Outside Sensor Fault Show causes & actionsIssue with outside sensor wiring or value. Likely causes
User action Restart Engineer action Securely connect the wiring at both the boiler and Outside Sensor Fit a new Outside Sensor Securely connect the wiring at the Terminal Block and the PCB Replace PCB Reset procedure RESTART PROCEDURE: TO RESTART BOILER PRESS THE RESTART BUTTON. | Details |
| Low Mains Voltage | Low Mains Voltage Show causes & actionsMains voltage supplied to the boiler is too low. Likely causes
User action Contact Electricity Provider Engineer action Contact Electricity Provider | Details |
| PCB Fault | PCB Fault Show causes & actionsIndicates a fault with the Printed Circuit Board. Likely causes
User action Restart Engineer action Contact Installer Replace PCB Reset procedure RESTART PROCEDURE: TO RESTART BOILER PRESS THE RESTART BUTTON. | Details |
| Spare PCB Not Set | Spare PCB Not Set Show causes & actionsNew PCB needs to be initialized. Likely causes
User action Switch Off Wait 5s Switch On Engineer action Follow instructions in Section 3.19 Reset procedure RESTART PROCEDURE: TO RESTART BOILER PRESS THE RESTART BUTTON. | Details |
| High Mains Voltage | High Mains Voltage Show causes & actionsMains voltage supplied to the boiler is too high. Likely causes
User action Contact Electricity Provider Engineer action Contact Electricity Provider | Details |
| Flow/Return Reversed | Flow/Return Reversed Show causes & actionsFlow and return pipes are connected incorrectly. Likely causes
User action Contact Installer Engineer action Check Return Thermistor | Details |
| Room Stat Fault | Room Stat Fault Show causes & actionsIssue with the room thermostat, possibly due to low batteries. Likely causes
User action Check Room Stat Batteries Engineer action Check Room Stat Batteries | Details |
| No CH operation but DHW operates OK | No CH operation but DHW operates OK Show causes & actionsCentral heating is not working, but domestic hot water is. Likely causes
Engineer action Move the mode knob to the Winter position Switch the Timer and Room Thermostat On Open the Radiator Valves There is no Voltage from the Timer/Room Stat. This is not boiler fault. Ensure Voltage is supplied to boiler by rectifying external wiring. Replace the Divertor Valve | Details |
| No DHW operation but CH operates OK | No DHW operation but CH operates OK Show causes & actionsDomestic hot water is not working, but central heating is. Likely causes
Engineer action Adjust flow rates to achieve 35° temp rise and check filter is not blocked with debris. Reconnect wiring or replace wiring harness if no continuity. Re-engage diverter head and secure clip to wateset Replace PCB Remove the turbine, and check for debris in the turbine & filter. Replace turbine if necessary. Is DHW OK? Replace turbine sensor Re-connect wiring Change diverter Valve motor | Details |
| No Display | No Display Show causes & actionsBoiler display is not working. Likely causes
Engineer action Supply power to the boiler Connect the wiring from the terminal block to the PCB securely. Replace the PCB? | Details |
Patterns that group across the manufacturer's fault-code table. Each entry links to the full code listing further down the page.
User: Fill system to 1.0 Bar
Engineer: Fill and vent the system and open all isolation valves, then restart boiler
Triggered by fault code Overheat Lockout 1/4.
User: Refill System to 1.0 Bar
Engineer: Bleed Radiators Refill System to 1.0 Bar Restart
Triggered by fault code Overheat Lockout 2/4.
User: Restart
Engineer: Check Radiator Valves And Boiler Valves Are Open Restart
Triggered by fault code Overheat Lockout 3/4.
User: Restart Boiler
Engineer: If Fault Persists Contact Installer
Triggered by fault code Overheat Lockout 4/4.
User: Check Other Gas Appliances Work Restart Boiler
Engineer: Check gas supply and rectify fault
Triggered by fault code Ignition Lockout 1/2.
Diagnostic checklists from engineer-submitted Ideal faults, with step-by-step checks and safety notes.
The Ideal Logic MAX Combi C24 is displaying an 'Overheat Lockout' fault (sometimes referred to as L1), with no heating or hot water and the…
The Ideal Vogue Max Combi 26 displaying 'IGNITION LOCKOUT' indicates that the boiler has failed to ignite after several attempts and has…
Common questions from engineers and homeowners about the Ideal Logic MAX Combi C35.
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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.