Fix & Repair Engineers provides professional support for Keston combi, system and heat-only boilers, including current twin-flue models and many older Keston installations.
Whether your Keston boiler has stopped working, is showing a fault code, needs its annual service or you are considering a replacement, our engineers can assess the appliance and heating system and recommend the appropriate next step.
Keston Boiler Engineers for Domestic and Commercial Heating Systems
Keston boilers are different from many conventional domestic boilers because of their distinctive twin-flue system.
Instead of combining the air intake and combustion-gas outlet inside one concentric flue, a Keston installation can use separate air and flue pipes. This makes Keston particularly useful where a boiler cannot easily be positioned beside an external wall or where the route to a suitable flue termination is unusually long or complicated.
That flexibility means Keston boilers are commonly encountered in properties such as:
- Flats and apartments
- Basements and internal boiler rooms
- Larger houses
- Listed and heritage buildings
- High-rise residential buildings
- Commercial premises
- Schools, churches and institutional buildings
- Plant rooms with difficult or extended flue routes
It also means servicing, repairing or replacing a Keston boiler requires careful consideration of the complete installation, not only the appliance on the wall.
Our engineers can inspect the boiler, controls, system condition and relevant twin-flue arrangement before recommending repair, servicing or replacement work.
Complete Keston Boiler Services
Keston Boiler Repairs
Systematic fault finding for no heating, no hot water, intermittent lockouts, pressure loss, fan faults, and error codes.
Keston Boiler Servicing
Regular maintenance according to appliance type, age, and manufacturer requirements for homeowners, landlords, and businesses.
Installation & Replacement
Comprehensive survey, twin-flue assessment, sizing, high-rise compliance, and professional installation commissioning.
Planned Maintenance
Scheduled servicing, condition assessments, and preventative maintenance for commercial plant rooms and property portfolios.
Keston Boiler Repairs
A Keston boiler breakdown can leave a home without heating and hot water or interrupt heating to an entire commercial property. Our engineers diagnose Keston boiler faults systematically rather than replacing components unnecessarily.
We can investigate problems including:
- Boiler not firing
- No central heating
- No hot water
- Intermittent lockouts
- Ignition and flame-loss faults
- Boiler losing pressure
- Water leaking from the boiler or heating system
- Fan and airflow faults
- Pump or circulation problems
- Overheating
- Thermistor and temperature-sensor faults
- Condensate drainage problems
- Unusual noises
- Control, programmer and thermostat faults
- PCB and electrical-control faults
- Flue or combustion-related problems
- Recurring Keston fault or error codes
Keston has used different fault-code systems across different boiler generations. When booking a repair, send us the exact fault code together with the boiler model where possible. This makes it easier to prepare for the diagnostic visit.
Keston Boiler Servicing
Regular servicing helps identify deterioration before it develops into a breakdown and allows the boiler's safety and operating condition to be assessed. A Keston service is carried out according to the appliance type, age, condition and manufacturer's servicing requirements.
Depending on the model and findings, servicing may include:
- Visual inspection of the boiler and installation
- Checking appliance condition and signs of deterioration
- Inspection of relevant seals and combustion components
- Burner and heat-exchanger assessment
- Flue and air-supply checks
- Combustion testing where required
- Condensate system inspection
- Checking boiler pressure
- Inspection of controls and safety functions
- Checking for leaks or corrosion
- Assessment of pumps and circulation where relevant
- Cleaning components where required by the manufacturer's instructions
- Operational testing
- Recording defects, advisories or recommended repairs
- Updating the appropriate service record where applicable
We can service Keston boilers for homeowners, landlords, managing agents, businesses and facilities managers.
Keston Boiler Installation and Replacement
Keston boilers are particularly useful where the position of the boiler or the required flue route makes a conventional installation difficult. If you are replacing an existing Keston boiler, we first assess the existing installation rather than assuming that a new boiler can simply be connected in exactly the same way.
The survey can consider:
- Existing boiler type and output
- Property heating and hot-water demand
- Current boiler position
- Twin-flue route and termination
- Condition and compliance of existing flue arrangements
- Flues passing through voids
- High-rise requirements where applicable
- Gas supply
- Heating-system condition
- System water quality
- Controls and zoning
- Hot-water cylinder requirements
- Condensate drainage
- Access for future servicing
- Manufacturer installation requirements
Keston Boiler Maintenance
For properties where heating reliability is operationally important, planned maintenance provides an alternative to waiting for equipment to fail. We can support:
- Scheduled annual servicing
- Preventative maintenance
- Condition assessments
- Multiple-boiler systems
- Commercial plant rooms
- Landlord property portfolios
- Managed residential buildings
- Facilities-management schedules
Maintenance visits can also highlight ageing equipment where repair expenditure, reliability and parts availability need to be considered against replacement.
Current Keston Boiler Range
Keston is part of Ideal Heating and its current range concentrates on British-built twin-flue gas boilers for domestic and light-commercial applications.
Keston Combi 2 C30 & C35
The Keston Combi 2 is available in 30kW and 35kW versions. It provides central heating and instantaneous domestic hot water from one appliance, making it suited to properties where a separate hot-water cylinder is not required. Its twin-flue arrangement can accommodate unusually challenging boiler locations, subject to the manufacturer's installation requirements.
- Keston Combi 2 servicing
- C30 and C35 repairs
- Fault diagnosis
- Replacement and installation
- Twin-flue assessment
- Planned maintenance
Keston System 2 S30
The Keston System 2 S30 is a 30kW system boiler designed to operate with a separate hot-water cylinder. It can be particularly suitable for larger properties where stored hot water is preferable to a combination boiler.
- System 2 S30 servicing
- Keston S30 repairs
- Pressure and circulation fault diagnosis
- Boiler replacement
- Twin-flue installation assessment
- Controls and system checks
Keston Heat 2 45 & 55
The Keston Heat 2 range provides 45kW and 55kW heat-only boilers for larger domestic and light-commercial heating systems. These boilers are relevant to properties where the heating load exceeds that of a typical domestic boiler or where a modular plant arrangement is required. Heat 2 boilers can also form part of Keston cascade installations, allowing multiple boilers to serve larger heating loads.
- Keston Heat 2 service and maintenance
- Heat 2 fault diagnosis
- Commercial Keston boiler repairs
- Boiler replacement
- Multiple-boiler and cascade maintenance
- Plant-room heating assessments
- Planned preventative maintenance
For commercial installations, provide the number of boilers, model numbers, approximate system output and details of any cascade controls when contacting us.
Older and Legacy Keston Boilers
Many properties across London and the South East still contain earlier Keston boilers. These can include older C-series, Celsius, Qudos and previous-generation Combi, System and Heat boilers.
Older Keston installations deserve particular care because the appliance, controls and flue arrangement may differ substantially from the current Keston range.
When attending a legacy boiler we consider:
- Exact model and age
- Fault history
- Appliance condition
- Existing twin-flue installation
- Parts availability
- Previous repairs
- Heating-system condition
- Cost of further repair
- Practical replacement options
We will not recommend replacing an older boiler simply because of its age. Where a safe and economical repair is practical, we can advise accordingly.
Conversely, repeated failures, poor overall condition or unavailable components can make further repair uneconomical. In these cases, we can assess replacement options while taking the existing Keston twin-flue arrangement into consideration.
Why Keston's Twin-Flue System Matters
The twin-flue system is one of the main reasons Keston boilers are found in installations that other boilers cannot easily accommodate.
Keston separates the combustion-air intake from the flue-gas outlet. Depending on the model and installation design, this allows significantly longer and more flexible routing than many conventional concentric boiler flues.
- Current Keston Combi 2 and System 2 models can support twin-flue configurations of up to 27 metres, subject to equivalent-length calculations and the manufacturer's installation instructions.
- Keston Heat 2 models provide twin-flue capability of up to 18 metres, again subject to the particular installation.
This can be useful when boilers are situated:
- In basements
- Away from an external wall
- In internal cupboards or plant rooms
- Within high-rise buildings
- Where external appearance is restricted
- In heritage or listed properties
- Where an existing building layout creates a difficult flue route
Twin-flue flexibility does not remove the need for careful design. Pipe specification, equivalent length, bends, gradient, joints, support, inspection access and termination position all need to be appropriate.
Replacing an Existing Keston Twin-Flue Boiler
Replacing an old Keston is often more complex than replacing a conventional boiler installed directly against an external wall.
One of the first questions is whether the existing boiler position can be retained. Modern Keston twin-flue boilers can often make this possible, avoiding major changes to heating pipework or the need to reposition the boiler solely to accommodate a conventional concentric flue.
However, the existing installation must be surveyed carefully. An engineer should determine:
Current Boiler Model
Which Keston model is currently installed.
System Type
Whether it is a combi, system or heat-only boiler.
Heating Output
Its required heating output.
Flue Length & Route
The route and approximate length of the existing air and flue pipes.
Route Suitability
Whether the existing route remains appropriate.
Inspection Access
Whether concealed flue sections can be inspected.
Building Compliance
Whether current installation and building requirements can be met.
Product Suitability
Whether a current Keston boiler remains the most appropriate replacement.
Only after these points are understood should a replacement boiler and installation method be specified.
Keston Boilers for High-Rise and Difficult Installations
Keston also manufactures a dedicated high-rise flue solution for compatible Combi and System boilers.
This is relevant because penetrations through the external walls of taller residential buildings can be subject to additional fire-safety requirements.
If you require a Keston replacement in a high-rise apartment or managed residential building, tell us:
- Building height if known
- Floor number
- Existing boiler model
- Boiler location
- Existing flue termination position
- Whether the freeholder or managing agent controls external-wall works
- Whether access permits or RAMS are required
This helps determine whether additional site information or approvals will be required before installation work can proceed.
Commercial Keston Boiler Service and Maintenance
Keston is not limited to small domestic installations.
The Heat 2 range is designed for larger domestic and light-commercial heating applications, while modular Heat 2 cascade configurations can serve significantly larger heating loads.
We can support Keston heating systems in:
Commercial boiler work may involve more than the appliance itself. System pumps, hydraulic separation, controls, sequencing, water quality, expansion provision and the wider heating installation can all affect boiler performance.
Where recurring boiler faults are caused by the wider system, repairing the boiler alone may not provide a lasting solution.
Annual Keston Servicing, Warranty & Fault Diagnosis
Keston requires its gas boilers to be serviced regularly by a Gas Safe registered engineer, and annual servicing forms part of the manufacturer's warranty conditions.
Current warranty terms vary according to the boiler model and installation. For example, Keston currently offers extended warranty arrangements on eligible Combi 2 and System 2 boilers when specific conditions such as system-filter installation and timely warranty registration are met. Keston Heat 2 has separate commissioning and warranty requirements.
Because warranty terms can change, the documentation supplied with your particular boiler should always take precedence. If maintaining the manufacturer's warranty is important, keep:
- Installation documentation
- Benchmark commissioning information
- Warranty-registration confirmation
- Annual service records
- Repair invoices and reports
Keston Boiler Fault Diagnosis
A fault code identifies the condition detected by the boiler. It does not necessarily identify the component that should be replaced.
For example, an ignition lockout could relate to several different parts of the combustion process. Repeated pressure loss may originate from the boiler or somewhere else in the heating system. A circulation-related fault may be caused by the pump, system restriction, air, valves or other hydraulic problems. That is why our repair process starts with diagnosis.
No heating or hot water
The boiler may have locked out or another part of the heating system may not be responding correctly.
Boiler continually losing pressure
Repeatedly repressurising the boiler without investigating the cause can conceal a leak, expansion problem or other system fault.
Ignition or flame-loss fault
This requires investigation of the relevant gas, ignition, combustion and control functions.
Fan or airflow fault
The boiler relies on the correct movement of combustion air and flue gases. Fan and flue faults should be investigated by a competent Gas Safe engineer.
Overheating or circulation fault
Restricted flow, pump problems, system contamination or temperature-sensing faults can contribute to overheating.
Condensate problems
Blocked or poorly draining condensate systems can cause boiler lockouts, particularly during cold weather.
Gas Safety & Keston Combi 2 / System 2 Safety Upgrade
Gas boilers must be installed, serviced and repaired by appropriately qualified Gas Safe registered engineers. This is particularly important with Keston installations because work can involve combustion, gas controls and unusually configured flue systems.
Never attempt to:
- Remove the boiler combustion cover
- Alter the gas valve
- Adjust combustion settings
- Bypass a boiler safety device
- Repair internal gas components
- Modify the twin-flue system
- Seal or alter flue joints
- Carry out combustion testing without the correct equipment and competence
Keston Combi 2 and System 2 Safety Upgrade
Keston published a manufacturer safety notice concerning a small number of Keston Combi 2 and System 2 boilers manufactured between August 2022 and 7 January 2024. The manufacturer introduced a safety upgrade for affected appliances. Keston stated that boilers in current production and Keston Heat boilers were not affected by the notice. If you have a Combi 2 or System 2 from this manufacturing period and are unsure whether the manufacturer upgrade was completed, check your boiler documentation or contact Keston using the appliance serial number. This manufacturer programme is separate from routine boiler servicing or repair work.
Our Keston Boiler Service Process
Tell Us About the Boiler
Provide the Keston model, fault code if displayed, property postcode and a short description of what is happening. A photograph of the boiler display and data plate can be useful.
Engineer Attendance
We arrange an appropriately qualified engineer to inspect the boiler and relevant parts of the heating installation.
Diagnosis or Service
For repairs, the engineer investigates the underlying cause of the fault. For servicing, the appliance is inspected and tested according to its model and manufacturer's requirements.
Clear Recommendation
We explain what has been found and whether repair, further investigation, maintenance or replacement is recommended. Where additional parts or work are required, this can be quoted before proceeding.
Repair, Testing and Documentation
Following approved work, the boiler is tested and relevant documentation or service information is provided.
Why Choose Fix & Repair Engineers for Your Keston Boiler?
- Gas Safe Registered Engineers: Gas boiler servicing, repair and installation is carried out by appropriately qualified Gas Safe registered engineers.
- Keston Twin-Flue Experience: We understand the practical differences between conventional boiler installations and Keston's separate air-intake and combustion-flue arrangement.
- Repair Before Replacement: A boiler fault does not automatically mean a new boiler is required. We diagnose the problem and advise whether repair remains practical.
- Domestic and Commercial Support: We work with homeowners, landlords, managing agents, businesses and facilities managers.
- Current and Older Keston Systems: Our work covers current Keston boilers as well as assessment of many older Keston installations, subject to appliance condition and parts availability.
- Clear Reporting: We provide practical information about the condition of the boiler, work completed and any further maintenance or repairs recommended.
Keston Boiler Service Across London and the Home Counties
Fix & Repair Engineers provides Keston boiler servicing, repair, maintenance and installation across London and the Home Counties.
Core coverage includes:
Attendance depends on the appliance, site requirements and engineer availability. For an accurate response, send us your postcode, Keston model and service requirement when making an enquiry.
What to Tell Us When Booking a Keston Engineer
Providing the right information helps us understand the installation before attendance. Where possible, send:
- Full postcode
- Keston boiler model
- Approximate boiler age
- Serial number if available
- Fault or error code
- Description of the problem
- Whether heating or hot water is still working
- Photographs of the boiler and display
- Whether the property is domestic or commercial
- Details of multiple boilers or a cascade arrangement
- Whether the boiler is in a plant room, basement or high-rise building
- Previous repair or service information if relevant
For installation enquiries, photographs of the existing boiler position and visible flue arrangement are particularly useful.